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cosmopolitan/third_party/stb/stb_image.c
Justine Tunney 957c61cbbf
Release Cosmopolitan v3.3 
This change upgrades to GCC 12.3 and GNU binutils 2.42. The GNU linker
appears to have changed things so that only a single de-duplicated str
table is present in the binary, and it gets placed wherever the linker
wants, regardless of what the linker script says. To cope with that we
need to stop using .ident to embed licenses. As such, this change does
significant work to revamp how third party licenses are defined in the
codebase, using `.section .notice,"aR",@progbits`.

This new GCC 12.3 toolchain has support for GNU indirect functions. It
lets us support __target_clones__ for the first time. This is used for
optimizing the performance of libc string functions such as strlen and
friends so far on x86, by ensuring AVX systems favor a second codepath
that uses VEX encoding. It shaves some latency off certain operations.
It's a useful feature to have for scientific computing for the reasons
explained by the test/libcxx/openmp_test.cc example which compiles for
fifteen different microarchitectures. Thanks to the upgrades, it's now
also possible to use newer instruction sets, such as AVX512FP16, VNNI.

Cosmo now uses the %gs register on x86 by default for TLS. Doing it is
helpful for any program that links `cosmo_dlopen()`. Such programs had
to recompile their binaries at startup to change the TLS instructions.
That's not great, since it means every page in the executable needs to
be faulted. The work of rewriting TLS-related x86 opcodes, is moved to
fixupobj.com instead. This is great news for MacOS x86 users, since we
previously needed to morph the binary every time for that platform but
now that's no longer necessary. The only platforms where we need fixup
of TLS x86 opcodes at runtime are now Windows, OpenBSD, and NetBSD. On
Windows we morph TLS to point deeper into the TIB, based on a TlsAlloc
assignment, and on OpenBSD/NetBSD we morph %gs back into %fs since the
kernels do not allow us to specify a value for the %gs register.

OpenBSD users are now required to use APE Loader to run Cosmo binaries
and assimilation is no longer possible. OpenBSD kernel needs to change
to allow programs to specify a value for the %gs register, or it needs
to stop marking executable pages loaded by the kernel as mimmutable().

This release fixes __constructor__, .ctor, .init_array, and lastly the
.preinit_array so they behave the exact same way as glibc.

We no longer use hex constants to define math.h symbols like M_PI.
2024-02-20 13:27:59 -08:00

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2023 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "third_party/stb/stb_image.h"
#include "libc/assert.h"
#include "libc/calls/calls.h"
#include "libc/fmt/conv.h"
#include "libc/serialize.h"
#include "libc/intrin/bswap.h"
#include "libc/limits.h"
#include "libc/log/gdb.h"
#include "libc/log/log.h"
#include "libc/macros.internal.h"
#include "libc/math.h"
#include "libc/mem/mem.h"
#include "libc/nexgen32e/x86feature.h"
#include "libc/runtime/runtime.h"
#include "libc/stdio/stdio.h"
#include "libc/str/str.h"
#include "libc/x/x.h"
#include "third_party/aarch64/arm_neon.internal.h"
#include "third_party/intel/ammintrin.internal.h"
__notice(stb_image_notice, "\
stb_image (Public Domain)\n\
Credit: Sean Barrett, et al.\n\
http://nothings.org/stb");
#ifdef __x86_64__
#define STBI_SSE2
#define idct_block_kernel stbi__idct_simd
#elif defined(__aarch64__)
#define STBI_NEON
#define idct_block_kernel stbi__idct_simd
#else
#define idct_block_kernel stbi__idct_block
#endif
#define ROL(w, k) (((w) << (k)) | ((w) >> (-(k) & (sizeof(w) * CHAR_BIT - 1))))
#ifndef STBI_MAX_DIMENSIONS
#define STBI_MAX_DIMENSIONS (1 << 24)
#endif
// stbi__context structure is our basic context used by all images, so it
// contains all the IO context, plus some basic image information
typedef struct {
uint32_t img_x, img_y;
int img_n, img_out_n;
stbi_io_callbacks io;
void *io_user_data;
int read_from_callbacks;
int buflen;
unsigned char buffer_start[128];
int callback_already_read;
unsigned char *img_buffer, *img_buffer_end;
unsigned char *img_buffer_original, *img_buffer_original_end;
} stbi__context;
static const unsigned char kPngSig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
static void stbi__refill_buffer(stbi__context *s);
// initialize a memory-decode context
static void stbi__start_mem(stbi__context *s, unsigned char const *buffer,
int len) {
s->io.read = NULL;
s->read_from_callbacks = 0;
s->callback_already_read = 0;
s->img_buffer = s->img_buffer_original = (unsigned char *)buffer;
s->img_buffer_end = s->img_buffer_original_end =
(unsigned char *)buffer + len;
}
// initialize a callback-based context
static void stbi__start_callbacks(stbi__context *s, stbi_io_callbacks *c,
void *user) {
s->io = *c;
s->io_user_data = user;
s->buflen = sizeof(s->buffer_start);
s->read_from_callbacks = 1;
s->callback_already_read = 0;
s->img_buffer = s->img_buffer_original = s->buffer_start;
stbi__refill_buffer(s);
s->img_buffer_original_end = s->img_buffer_end;
}
static int stbi__stdio_read(void *user, char *data, int size) {
return fread(data, 1, size, user);
}
static void stbi__stdio_skip(void *user, int n) {
int ch;
fseek(user, n, SEEK_CUR);
ch = fgetc(user);
if (ch != EOF) {
ungetc(ch, user);
}
}
static int stbi__stdio_eof(void *user) {
return feof(user) || ferror(user);
}
static stbi_io_callbacks stbi__stdio_callbacks = {
stbi__stdio_read,
stbi__stdio_skip,
stbi__stdio_eof,
};
static void stbi__start_file(stbi__context *s, FILE *f) {
stbi__start_callbacks(s, &stbi__stdio_callbacks, (void *)f);
}
static void stbi__rewind(stbi__context *s) {
// conceptually rewind SHOULD rewind to the beginning of the stream,
// but we just rewind to the beginning of the initial buffer, because
// we only use it after doing 'test', which only ever looks at at most 92
// bytes
s->img_buffer = s->img_buffer_original;
s->img_buffer_end = s->img_buffer_original_end;
}
enum { STBI_ORDER_RGB, STBI_ORDER_BGR };
typedef struct {
int bits_per_channel;
int num_channels;
} stbi__result_info;
static int stbi__jpeg_test(stbi__context *);
static void *stbi__jpeg_load(stbi__context *, int *, int *, int *, int,
stbi__result_info *);
static int stbi__jpeg_info(stbi__context *, int *, int *, int *);
static int stbi__png_test(stbi__context *);
static void *stbi__png_load(stbi__context *, int *, int *, int *, int,
stbi__result_info *);
static int stbi__png_info(stbi__context *, int *, int *, int *);
static int stbi__png_is16(stbi__context *);
static int stbi__gif_test(stbi__context *);
static void *stbi__gif_load(stbi__context *, int *, int *, int *, int,
stbi__result_info *);
static void *stbi__load_gif_main(stbi__context *, int **, int *, int *, int *,
int *, int);
static int stbi__gif_info(stbi__context *, int *, int *, int *);
static int stbi__pnm_test(stbi__context *);
static void *stbi__pnm_load(stbi__context *, int *, int *, int *, int,
stbi__result_info *);
static int stbi__pnm_info(stbi__context *, int *, int *, int *);
static const char *stbi__g_failure_reason;
static int stbi__vertically_flip_on_load = 0;
const char *stbi_failure_reason(void) {
return stbi__g_failure_reason;
}
static int stbi__err(const char *specific_details,
const char *general_details) {
// DebugBreak();
// WARNF("%s: %s", general_details, specific_details);
stbi__g_failure_reason = general_details;
return 0;
}
// stb_image uses ints pervasively, including for offset calculations.
// therefore the largest decoded image size we can support with the
// current code, even on 64-bit targets, is INT_MAX. this is not a
// significant limitation for the intended use case.
//
// we do, however, need to make sure our size calculations don't
// overflow. hence a few helper functions for size calculations that
// multiply integers together, making sure that they're non-negative
// and no overflow occurs.
// return 1 if the sum is valid, 0 on overflow.
// negative terms are considered invalid.
static int stbi__addsizes_valid(int a, int b) {
if (b < 0) return 0;
// now 0 <= b <= INT_MAX, hence also
// 0 <= INT_MAX - b <= INTMAX.
// And "a + b <= INT_MAX" (which might overflow) is the
// same as a <= INT_MAX - b (no overflow)
return a <= INT_MAX - b;
}
// returns 1 if the product is valid, 0 on overflow.
// negative factors are considered invalid.
static int stbi__mul2sizes_valid(int a, int b) {
if (a < 0 || b < 0) return 0;
if (b == 0) return 1; // mul-by-0 is always safe
// portable way to check for no overflows in a*b
return a <= INT_MAX / b;
}
// returns 1 if "a * b + add" has no negative terms/factors
// and doesn't overflow
static int stbi__mad2sizes_valid(int a, int b, int add) {
return stbi__mul2sizes_valid(a, b) && stbi__addsizes_valid(a * b, add);
}
// returns 1 if "a * b * c + add" has no negative terms/factors
// and doesn't overflow
static int stbi__mad3sizes_valid(int a, int b, int c, int add) {
return stbi__mul2sizes_valid(a, b) && stbi__mul2sizes_valid(a * b, c) &&
stbi__addsizes_valid(a * b * c, add);
}
// returns 1 if "a * b * c * d + add" has no negative terms/factors
// and doesn't overflow
static int stbi__mad4sizes_valid(int a, int b, int c, int d, int add) {
return stbi__mul2sizes_valid(a, b) && stbi__mul2sizes_valid(a * b, c) &&
stbi__mul2sizes_valid(a * b * c, d) &&
stbi__addsizes_valid(a * b * c * d, add);
}
// mallocs with size overflow checking
static void *stbi__malloc_mad2(int a, int b, int add) {
if (!stbi__mad2sizes_valid(a, b, add)) return NULL;
return xmalloc(a * b + add);
}
static void *stbi__malloc_mad3(int a, int b, int c, int add) {
if (!stbi__mad3sizes_valid(a, b, c, add)) return NULL;
return xmalloc(a * b * c + add);
}
static void *stbi__malloc_mad4(int a, int b, int c, int d, int add) {
if (!stbi__mad4sizes_valid(a, b, c, d, add)) return NULL;
return xmalloc(a * b * c * d + add);
}
// returns 1 if the sum of two signed ints is valid
// (between -2^31 and 2^31-1 inclusive), 0 on overflow.
static int stbi__addints_valid(int a, int b) {
if ((a >= 0) != (b >= 0)) {
// a and b have different signs, so no overflow
return 1;
}
if (a < 0 && b < 0) {
// same as a + b >= INT_MIN; INT_MIN - b cannot overflow since b < 0.
return a >= INT_MIN - b;
}
return a <= INT_MAX - b;
}
// returns 1 if the product of two ints fits in a signed short,
// 0 on overflow.
static int stbi__mul2shorts_valid(int a, int b) {
if (b == 0 || b == -1) {
// multiplication by 0 is always 0;
// check for -1 so SHRT_MIN / b doesn't overflow
return 1;
}
if ((a >= 0) == (b >= 0)) {
// product is positive, so similar to mul2sizes_valid
return a <= SHRT_MAX / b;
}
if (b < 0) {
// same as a * b >= SHRT_MIN
return a <= SHRT_MIN / b;
}
return a >= SHRT_MIN / b;
}
#define stbi__errpf(x, y) \
({ \
stbi__err(x, y); \
NULL; \
})
#define stbi__errpuc(x, y) \
({ \
stbi__err(x, y); \
NULL; \
})
void stbi_image_free(void *retval_from_stbi_load) {
free(retval_from_stbi_load);
}
void stbi_set_flip_vertically_on_load(int flag_true_if_should_flip) {
stbi__vertically_flip_on_load = flag_true_if_should_flip;
}
static void *stbi__load_main(stbi__context *s, int *x, int *y, int *comp,
int req_comp, stbi__result_info *ri) {
bzero(ri, sizeof(*ri));
ri->bits_per_channel = 8;
ri->num_channels = 0;
// test the formats with a very explicit header first (at least a FOURCC
// or distinctive magic number first)
if (stbi__png_test(s)) return stbi__png_load(s, x, y, comp, req_comp, ri);
if (stbi__gif_test(s)) return stbi__gif_load(s, x, y, comp, req_comp, ri);
// then the formats that can end up attempting to load with just 1 or 2
// bytes matching expectations; these are prone to false positives, so
// try them later
if (stbi__jpeg_test(s)) return stbi__jpeg_load(s, x, y, comp, req_comp, ri);
if (stbi__pnm_test(s)) return stbi__pnm_load(s, x, y, comp, req_comp, ri);
return stbi__errpuc("unknown image type",
"Image not of any known type, or corrupt");
}
unsigned char *stbi__convert_16_to_8(uint16_t *orig, int w, int h,
int channels) {
int i;
int img_len = w * h * channels;
unsigned char *reduced = xmalloc(img_len);
for (i = 0; i < img_len; ++i) {
// top half of each byte is sufficient
// approx of 16->8 bit scaling
reduced[i] = (orig[i] >> 8) & 0xff;
}
free(orig);
return reduced;
}
uint16_t *stbi__convert_8_to_16(unsigned char *orig, int w, int h,
int channels) {
int i;
int img_len = w * h * channels;
uint16_t *enlarged = xmalloc(img_len * 2);
for (i = 0; i < img_len; ++i) {
// replicate to high and low byte, maps 0->0, 255->0xffff
enlarged[i] = (uint16_t)((orig[i] << 8) + orig[i]);
}
free(orig);
return enlarged;
}
static void stbi__vertical_flip(void *image, int w, int h,
int bytes_per_pixel) {
int row;
size_t bytes_per_row, bytes_left, bytes_copy;
unsigned char *row0, *row1, *bytes, temp[2048];
bytes = image;
bytes_per_row = bytes_per_pixel * w;
for (row = 0; row < (h >> 1); row++) {
row0 = bytes + row * bytes_per_row;
row1 = bytes + (h - row - 1) * bytes_per_row;
// swap row0 with row1
bytes_left = bytes_per_row;
while (bytes_left) {
bytes_copy = bytes_left < sizeof(temp) ? bytes_left : sizeof(temp);
memcpy(temp, row0, bytes_copy);
memcpy(row0, row1, bytes_copy);
memcpy(row1, temp, bytes_copy);
row0 += bytes_copy;
row1 += bytes_copy;
bytes_left -= bytes_copy;
}
}
}
static void stbi__vertical_flip_slices(void *image, int w, int h, int z,
int bytes_per_pixel) {
unsigned char *bytes;
int slice, slice_size;
bytes = image;
slice_size = w * h * bytes_per_pixel;
for (slice = 0; slice < z; ++slice) {
stbi__vertical_flip(bytes, w, h, bytes_per_pixel);
bytes += slice_size;
}
}
static unsigned char *stbi__load_and_postprocess_8bit(stbi__context *s, int *x,
int *y, int *comp,
int req_comp) {
void *result;
stbi__result_info ri;
result = stbi__load_main(s, x, y, comp, req_comp, &ri);
if (result == NULL) return NULL;
assert(ri.bits_per_channel == 8 || ri.bits_per_channel == 16);
if (ri.bits_per_channel != 8) {
// https://github.com/nothings/stb/pull/1497
unsigned char *converted = stbi__convert_16_to_8(
(uint16_t *)result, *x, *y, req_comp == 0 ? *comp : req_comp);
if (converted == NULL) {
free(result);
return NULL;
}
result = converted;
ri.bits_per_channel = 8;
}
// @TODO: move stbi__convert_format to here
if (stbi__vertically_flip_on_load) {
int channels = req_comp ? req_comp : *comp;
stbi__vertical_flip(result, *x, *y, channels * sizeof(unsigned char));
}
return (unsigned char *)result;
}
static uint16_t *stbi__load_and_postprocess_16bit(stbi__context *s, int *x,
int *y, int *comp,
int req_comp) {
void *result;
stbi__result_info ri;
result = stbi__load_main(s, x, y, comp, req_comp, &ri);
if (result == NULL) return NULL;
assert(ri.bits_per_channel == 8 || ri.bits_per_channel == 16);
if (ri.bits_per_channel != 16) {
// https://github.com/nothings/stb/pull/1497
uint16_t *converted = stbi__convert_8_to_16(
(unsigned char *)result, *x, *y, req_comp == 0 ? *comp : req_comp);
if (converted == NULL) {
free(result);
return NULL;
}
result = converted;
ri.bits_per_channel = 16;
}
// @TODO: move stbi__convert_format16 to here
// @TODO: special case RGB-to-Y (and RGBA-to-YA) for 8-bit-to-16-bit case to
// keep more precision
if (stbi__vertically_flip_on_load) {
int channels = req_comp ? req_comp : *comp;
stbi__vertical_flip(result, *x, *y, channels * sizeof(uint16_t));
}
return (uint16_t *)result;
}
static FILE *stbi__fopen(char const *filename, char const *mode) {
return fopen(filename, mode);
}
unsigned char *stbi_load(char const *filename, int *x, int *y, int *comp,
int req_comp) {
FILE *f = stbi__fopen(filename, "rb");
unsigned char *result;
if (!f) return stbi__errpuc("can't fopen", "Unable to open file");
result = stbi_load_from_file(f, x, y, comp, req_comp);
fclose(f);
return result;
}
unsigned char *stbi_load_from_file(FILE *f, int *x, int *y, int *comp,
int req_comp) {
unsigned char *result;
stbi__context s;
stbi__start_file(&s, f);
result = stbi__load_and_postprocess_8bit(&s, x, y, comp, req_comp);
if (result) {
// need to 'unget' all the characters in the IO buffer
// https://github.com/nothings/stb/pull/1420
if (fseek(f, -(int)(s.img_buffer_end - s.img_buffer), SEEK_CUR)) {
// fseek() failed; we can no longer maintain the file cursor position
// guarantee of this function, so return null.
free(result);
return stbi__errpuc("bad file",
"fseek() failed; seek position unreliable");
}
}
return result;
}
uint16_t *stbi_load_from_file_16(FILE *f, int *x, int *y, int *comp,
int req_comp) {
uint16_t *result;
stbi__context s;
stbi__start_file(&s, f);
result = stbi__load_and_postprocess_16bit(&s, x, y, comp, req_comp);
if (result) {
// need to 'unget' all the characters in the IO buffer
// https://github.com/nothings/stb/pull/1420
if (fseek(f, -(int)(s.img_buffer_end - s.img_buffer), SEEK_CUR)) {
// fseek() failed; we can no longer maintain the file cursor position
// guarantee of this function, so return null.
free(result);
return (uint16_t *)stbi__errpuc(
"bad file", "fseek() failed; seek position unreliable");
}
}
return result;
}
unsigned short *stbi_load_16(char const *filename, int *x, int *y, int *comp,
int req_comp) {
FILE *f = stbi__fopen(filename, "rb");
uint16_t *result;
if (!f) return stbi__errpuc("can't fopen", "Unable to open file");
result = stbi_load_from_file_16(f, x, y, comp, req_comp);
fclose(f);
return result;
}
unsigned short *stbi_load_16_from_memory(unsigned char const *buffer, int len,
int *x, int *y, int *channels_in_file,
int desired_channels) {
stbi__context s;
stbi__start_mem(&s, buffer, len);
return stbi__load_and_postprocess_16bit(&s, x, y, channels_in_file,
desired_channels);
}
unsigned short *stbi_load_16_from_callbacks(stbi_io_callbacks const *clbk,
void *user, int *x, int *y,
int *channels_in_file,
int desired_channels) {
stbi__context s;
stbi__start_callbacks(&s, (stbi_io_callbacks *)clbk, user);
return stbi__load_and_postprocess_16bit(&s, x, y, channels_in_file,
desired_channels);
}
unsigned char *stbi_load_from_memory(unsigned char const *buffer, int len,
int *x, int *y, int *comp, int req_comp) {
stbi__context s;
stbi__start_mem(&s, buffer, len);
return stbi__load_and_postprocess_8bit(&s, x, y, comp, req_comp);
}
unsigned char *stbi_load_from_callbacks(stbi_io_callbacks const *clbk,
void *user, int *x, int *y, int *comp,
int req_comp) {
stbi__context s;
stbi__start_callbacks(&s, (stbi_io_callbacks *)clbk, user);
return stbi__load_and_postprocess_8bit(&s, x, y, comp, req_comp);
}
unsigned char *stbi_load_gif_from_memory(unsigned char const *buffer, int len,
int **delays, int *x, int *y, int *z,
int *comp, int req_comp) {
unsigned char *result;
stbi__context s;
stbi__start_mem(&s, buffer, len);
result =
(unsigned char *)stbi__load_gif_main(&s, delays, x, y, z, comp, req_comp);
if (stbi__vertically_flip_on_load) {
stbi__vertical_flip_slices(result, *x, *y, *z, *comp);
}
return result;
}
enum { STBI__SCAN_load = 0, STBI__SCAN_type, STBI__SCAN_header };
static void stbi__refill_buffer(stbi__context *s) {
int n = (s->io.read)(s->io_user_data, (char *)s->buffer_start, s->buflen);
s->callback_already_read += (int)(s->img_buffer - s->img_buffer_original);
if (n == 0) {
// at end of file, treat same as if from memory, but need to handle case
// where s->img_buffer isn't pointing to safe memory, e.g. 0-byte file
s->read_from_callbacks = 0;
s->img_buffer = s->buffer_start;
s->img_buffer_end = s->buffer_start + 1;
*s->img_buffer = 0;
} else {
s->img_buffer = s->buffer_start;
s->img_buffer_end = s->buffer_start + n;
}
}
forceinline unsigned char stbi__get8(stbi__context *s) {
if (s->img_buffer < s->img_buffer_end) return *s->img_buffer++;
if (s->read_from_callbacks) {
stbi__refill_buffer(s);
return *s->img_buffer++;
}
return 0;
}
forceinline int stbi__at_eof(stbi__context *s) {
if (s->io.read) {
if (!(s->io.eof)(s->io_user_data)) return 0;
// if feof() is true, check if buffer = end
// special case: we've only got the special 0 character at the end
if (s->read_from_callbacks == 0) return 1;
}
return s->img_buffer >= s->img_buffer_end;
}
static void stbi__skip(stbi__context *s, int n) {
if (n == 0) return; // already there!
if (n < 0) {
s->img_buffer = s->img_buffer_end;
return;
}
if (s->io.read) {
int blen = (int)(s->img_buffer_end - s->img_buffer);
if (blen < n) {
s->img_buffer = s->img_buffer_end;
(s->io.skip)(s->io_user_data, n - blen);
return;
}
}
s->img_buffer += n;
}
static int stbi__getn(stbi__context *s, unsigned char *buffer, int n) {
if (s->io.read) {
int blen = (int)(s->img_buffer_end - s->img_buffer);
if (blen < n) {
int res, count;
memcpy(buffer, s->img_buffer, blen);
count = (s->io.read)(s->io_user_data, (char *)buffer + blen, n - blen);
res = (count == (n - blen));
s->img_buffer = s->img_buffer_end;
return res;
}
}
if (s->img_buffer + n <= s->img_buffer_end) {
memcpy(buffer, s->img_buffer, n);
s->img_buffer += n;
return 1;
} else {
return 0;
}
}
static int stbi__get16le(stbi__context *s) {
int z = stbi__get8(s);
return z + (stbi__get8(s) << 8);
}
static int stbi__get16be(stbi__context *s) {
int z = stbi__get8(s);
return (z << 8) + stbi__get8(s);
}
static uint32_t stbi__get32be(stbi__context *s) {
uint32_t z = stbi__get16be(s);
return (z << 16) + stbi__get16be(s);
}
#define STBI__BYTECAST(x) \
((unsigned char)((x)&255)) // truncate int to byte without warnings
//////////////////////////////////////////////////////////////////////////////
//
// generic converter from built-in img_n to req_comp
// individual types do this automatically as much as possible (e.g. jpeg
// does all cases internally since it needs to colorspace convert anyway,
// and it never has alpha, so very few cases). png can automatically
// interleave an alpha=255 channel, but falls back to this for other cases
//
// assume data buffer is malloced, so malloc a new one and free that one
// only failure mode is malloc failing
static unsigned char stbi__compute_y(int r, int g, int b) {
return (unsigned char)(((r * 77) + (g * 150) + (29 * b)) >> 8);
}
static unsigned char *stbi__convert_format(unsigned char *data, int img_n,
int req_comp, unsigned int x,
unsigned int y) {
int i, j;
unsigned char *good, *src, *dest;
if (req_comp == img_n) return data;
assert(req_comp >= 1 && req_comp <= 4);
good = stbi__malloc_mad3(req_comp, x, y, 0);
for (j = 0; j < (int)y; ++j) {
src = data + j * x * img_n;
dest = good + j * x * req_comp;
#define STBI__COMBO(a, b) ((a)*8 + (b))
#define STBI__CASE(a, b) \
case STBI__COMBO(a, b): \
for (i = x - 1; i >= 0; --i, src += a, dest += b)
// convert source image with img_n components to one with req_comp
// components; avoid switch per pixel, so use switch per scanline and
// massive macros
switch (STBI__COMBO(img_n, req_comp)) {
STBI__CASE(1, 2) {
dest[0] = src[0];
dest[1] = 255;
}
break;
STBI__CASE(1, 3) {
dest[0] = dest[1] = dest[2] = src[0];
}
break;
STBI__CASE(1, 4) {
dest[0] = dest[1] = dest[2] = src[0];
dest[3] = 255;
}
break;
STBI__CASE(2, 1) {
dest[0] = src[0];
}
break;
STBI__CASE(2, 3) {
dest[0] = dest[1] = dest[2] = src[0];
}
break;
STBI__CASE(2, 4) {
dest[0] = dest[1] = dest[2] = src[0];
dest[3] = src[1];
}
break;
STBI__CASE(3, 4) {
dest[0] = src[0];
dest[1] = src[1];
dest[2] = src[2];
dest[3] = 255;
}
break;
STBI__CASE(3, 1) {
dest[0] = stbi__compute_y(src[0], src[1], src[2]);
}
break;
STBI__CASE(3, 2) {
dest[0] = stbi__compute_y(src[0], src[1], src[2]);
dest[1] = 255;
}
break;
STBI__CASE(4, 1) {
dest[0] = stbi__compute_y(src[0], src[1], src[2]);
}
break;
STBI__CASE(4, 2) {
dest[0] = stbi__compute_y(src[0], src[1], src[2]);
dest[1] = src[3];
}
break;
STBI__CASE(4, 3) {
dest[0] = src[0];
dest[1] = src[1];
dest[2] = src[2];
}
break;
default:
assert(0);
free(data);
free(good);
return stbi__errpuc("unsupported", "Unsupported format conversion");
}
#undef STBI__CASE
}
free(data);
return good;
}
static uint16_t stbi__compute_y_16(int r, int g, int b) {
return (uint16_t)(((r * 77) + (g * 150) + (29 * b)) >> 8);
}
static uint16_t *stbi__convert_format16(uint16_t *data, int img_n, int req_comp,
unsigned int x, unsigned int y) {
int i, j;
uint16_t *good;
if (req_comp == img_n) return data;
assert(req_comp >= 1 && req_comp <= 4);
good = xmalloc(req_comp * x * y * 2);
for (j = 0; j < (int)y; ++j) {
uint16_t *src = data + j * x * img_n;
uint16_t *dest = good + j * x * req_comp;
#define STBI__COMBO(a, b) ((a)*8 + (b))
#define STBI__CASE(a, b) \
case STBI__COMBO(a, b): \
for (i = x - 1; i >= 0; --i, src += a, dest += b)
// convert source image with img_n components to one with req_comp
// components; avoid switch per pixel, so use switch per scanline and
// massive macros
switch (STBI__COMBO(img_n, req_comp)) {
STBI__CASE(1, 2) {
dest[0] = src[0];
dest[1] = 0xffff;
}
break;
STBI__CASE(1, 3) {
dest[0] = dest[1] = dest[2] = src[0];
}
break;
STBI__CASE(1, 4) {
dest[0] = dest[1] = dest[2] = src[0];
dest[3] = 0xffff;
}
break;
STBI__CASE(2, 1) {
dest[0] = src[0];
}
break;
STBI__CASE(2, 3) {
dest[0] = dest[1] = dest[2] = src[0];
}
break;
STBI__CASE(2, 4) {
dest[0] = dest[1] = dest[2] = src[0];
dest[3] = src[1];
}
break;
STBI__CASE(3, 4) {
dest[0] = src[0];
dest[1] = src[1];
dest[2] = src[2];
dest[3] = 0xffff;
}
break;
STBI__CASE(3, 1) {
dest[0] = stbi__compute_y_16(src[0], src[1], src[2]);
}
break;
STBI__CASE(3, 2) {
dest[0] = stbi__compute_y_16(src[0], src[1], src[2]);
dest[1] = 0xffff;
}
break;
STBI__CASE(4, 1) {
dest[0] = stbi__compute_y_16(src[0], src[1], src[2]);
}
break;
STBI__CASE(4, 2) {
dest[0] = stbi__compute_y_16(src[0], src[1], src[2]);
dest[1] = src[3];
}
break;
STBI__CASE(4, 3) {
dest[0] = src[0];
dest[1] = src[1];
dest[2] = src[2];
}
break;
default:
assert(0);
free(data);
free(good);
return (uint16_t *)stbi__errpuc("unsupported",
"Unsupported format conversion");
}
#undef STBI__CASE
}
free(data);
return good;
}
//////////////////////////////////////////////////////////////////////////////
//
// "baseline" JPEG/JFIF decoder
//
// simple implementation
// - doesn't support delayed output of y-dimension
// - simple interface (only one output format: 8-bit interleaved RGB)
// - doesn't try to recover corrupt jpegs
// - doesn't allow partial loading, loading multiple at once
// - still fast on x86 (copying globals into locals doesn't help x86)
// - allocates lots of intermediate memory (full size of all components)
// - non-interleaved case requires this anyway
// - allows good upsampling (see next)
// high-quality
// - upsampled channels are bilinearly interpolated, even across blocks
// - quality integer IDCT derived from IJG's 'slow'
// performance
// - fast huffman; reasonable integer IDCT
// - some SIMD kernels for common paths on targets with SSE2/NEON
// - uses a lot of intermediate memory, could cache poorly
// huffman decoding acceleration
#define FAST_BITS 9 // larger handles more cases; smaller stomps less cache
typedef struct {
unsigned char fast[1 << FAST_BITS];
// weirdly, repacking this into AoS is a 10% speed loss, instead of a win
uint16_t code[256];
unsigned char values[256];
unsigned char size[257];
unsigned int maxcode[18];
int delta[17]; // old 'firstsymbol' - old 'firstcode'
} stbi__huffman;
typedef struct {
stbi__context *s;
stbi__huffman huff_dc[4];
stbi__huffman huff_ac[4];
uint16_t dequant[4][64];
int16_t fast_ac[4][1 << FAST_BITS];
// sizes for components, interleaved MCUs
int img_h_max, img_v_max;
int img_mcu_x, img_mcu_y;
int img_mcu_w, img_mcu_h;
// definition of jpeg image component
struct {
int id;
int h, v;
int tq;
int hd, ha;
int dc_pred;
int x, y, w2, h2;
unsigned char *data;
unsigned char *linebuf;
short *coeff; // progressive only
int coeff_w, coeff_h; // number of 8x8 coefficient blocks
} img_comp[4];
uint32_t code_buffer; // jpeg entropy-coded buffer
int code_bits; // number of valid bits
unsigned char marker; // marker seen while filling entropy buffer
int nomore; // flag if we saw a marker so must stop
int progressive;
int spec_start;
int spec_end;
int succ_high;
int succ_low;
int eob_run;
int jfif;
int app14_color_transform; // Adobe APP14 tag
int rgb;
int scan_n, order[4];
int restart_interval, todo;
// kernels
unsigned char *(*resample_row_hv_2_kernel)(unsigned char *out,
unsigned char *in_near,
unsigned char *in_far, int w,
int hs);
} stbi__jpeg;
static int stbi__build_huffman(stbi__huffman *h, int *count) {
int i, j, k = 0;
unsigned int code;
// build size list for each symbol (from JPEG spec)
for (i = 0; i < 16; ++i) {
for (j = 0; j < count[i]; ++j) {
h->size[k++] = (unsigned char)(i + 1);
if (k >= 257) {
return stbi__err("bad size list", "Corrupt JPEG");
}
}
}
h->size[k] = 0;
// compute actual symbols (from jpeg spec)
code = 0;
k = 0;
for (j = 1; j <= 16; ++j) {
// compute delta to add to code to compute symbol id
h->delta[j] = k - code;
if (h->size[k] == j) {
while (h->size[k] == j) h->code[k++] = (uint16_t)(code++);
if (code - 1 >= (1u << j)) {
return stbi__err("bad code lengths", "Corrupt JPEG");
}
}
// compute largest code + 1 for this size, preshifted as needed later
h->maxcode[j] = code << (16 - j);
code <<= 1;
}
h->maxcode[j] = 0xffffffff;
// build non-spec acceleration table; 255 is flag for not-accelerated
memset(h->fast, 255, 1 << FAST_BITS);
for (i = 0; i < k; ++i) {
int s = h->size[i];
if (s <= FAST_BITS) {
int c = h->code[i] << (FAST_BITS - s);
int m = 1 << (FAST_BITS - s);
for (j = 0; j < m; ++j) {
h->fast[c + j] = (unsigned char)i;
}
}
}
return 1;
}
// build a table that decodes both magnitude and value of small ACs in
// one go.
static void stbi__build_fast_ac(int16_t *fast_ac, stbi__huffman *h) {
int i;
for (i = 0; i < (1 << FAST_BITS); ++i) {
unsigned char fast = h->fast[i];
fast_ac[i] = 0;
if (fast < 255) {
int rs = h->values[fast];
int run = (rs >> 4) & 15;
int magbits = rs & 15;
int len = h->size[fast];
if (magbits && len + magbits <= FAST_BITS) {
// magnitude code followed by receive_extend code
int k = ((i << len) & ((1 << FAST_BITS) - 1)) >> (FAST_BITS - magbits);
int m = 1 << (magbits - 1);
if (k < m) k += (~0U << magbits) + 1;
// if the result is small enough, we can fit it in fast_ac table
if (k >= -128 && k <= 127)
fast_ac[i] = (int16_t)((k * 256) + (run * 16) + (len + magbits));
}
}
}
}
static void stbi__grow_buffer_unsafe(stbi__jpeg *j) {
do {
unsigned b = j->nomore ? 0 : stbi__get8(j->s);
if (b == 0xff) {
int c = stbi__get8(j->s);
while (c == 0xff) c = stbi__get8(j->s); // consume fill bytes
if (c != 0) {
j->marker = (unsigned char)c;
j->nomore = 1;
return;
}
}
j->code_buffer |= b << (24 - j->code_bits);
j->code_bits += 8;
} while (j->code_bits <= 24);
}
// (1 << n) - 1
static const uint32_t stbi__bmask[17] = {0, 1, 3, 7, 15, 31,
63, 127, 255, 511, 1023, 2047,
4095, 8191, 16383, 32767, 65535};
// decode a jpeg huffman value from the bitstream
forceinline int stbi__jpeg_huff_decode(stbi__jpeg *j, stbi__huffman *h) {
unsigned int temp;
int c, k;
if (j->code_bits < 16) stbi__grow_buffer_unsafe(j);
// look at the top FAST_BITS and determine what symbol ID it is,
// if the code is <= FAST_BITS
c = (j->code_buffer >> (32 - FAST_BITS)) & ((1 << FAST_BITS) - 1);
k = h->fast[c];
if (k < 255) {
int s = h->size[k];
if (s > j->code_bits) return -1;
j->code_buffer <<= s;
j->code_bits -= s;
return h->values[k];
}
// naive test is to shift the code_buffer down so k bits are
// valid, then test against maxcode. To speed this up, we've
// preshifted maxcode left so that it has (16-k) 0s at the
// end; in other words, regardless of the number of bits, it
// wants to be compared against something shifted to have 16;
// that way we don't need to shift inside the loop.
temp = j->code_buffer >> 16;
for (k = FAST_BITS + 1;; ++k)
if (temp < h->maxcode[k]) break;
if (k == 17) {
WARNF("j->code_bits: %d", j->code_bits);
// error! code not found
j->code_bits -= 16;
WARNF("Symbol: %d", k);
return -1;
}
if (k > j->code_bits) return -1;
// convert the huffman code to the symbol id
c = ((j->code_buffer >> (32 - k)) & stbi__bmask[k]) + h->delta[k];
if (c < 0 || c >= 256) {
// symbol id out of bounds!
return -1;
}
assert((((j->code_buffer) >> (32 - h->size[c])) & stbi__bmask[h->size[c]]) ==
h->code[c]);
// convert the id to a symbol
j->code_bits -= k;
j->code_buffer <<= k;
return h->values[c];
}
// bias[n] = (-1 << n) + 1
static const int stbi__jbias[16] = {0, -1, -3, -7, -15, -31,
-63, -127, -255, -511, -1023, -2047,
-4095, -8191, -16383, -32767};
// combined JPEG 'receive' and JPEG 'extend', since baseline
// always extends everything it receives.
forceinline int stbi__extend_receive(stbi__jpeg *j, int n) {
int sgn;
unsigned int k;
if (j->code_bits < n) stbi__grow_buffer_unsafe(j);
if (j->code_bits < n) {
// ran out of bits from stream, return 0s intead of continuing
return 0;
}
// sign bit is always in MSB;
// 0 if MSB clear (positive), 1 if MSB set (negative)
sgn = j->code_buffer >> 31;
k = ROL(j->code_buffer, n);
j->code_buffer = k & ~stbi__bmask[n];
k &= stbi__bmask[n];
j->code_bits -= n;
return k + (stbi__jbias[n] & (sgn - 1));
}
// get some unsigned bits
forceinline int stbi__jpeg_get_bits(stbi__jpeg *j, int n) {
unsigned int k;
if (j->code_bits < n) stbi__grow_buffer_unsafe(j);
if (j->code_bits < n) {
// ran out of bits from stream, return 0s intead of continuing
return 0;
}
k = ROL(j->code_buffer, n);
j->code_buffer = k & ~stbi__bmask[n];
k &= stbi__bmask[n];
j->code_bits -= n;
return k;
}
forceinline int stbi__jpeg_get_bit(stbi__jpeg *j) {
unsigned int k;
if (j->code_bits < 1) stbi__grow_buffer_unsafe(j);
if (j->code_bits < 1) {
// ran out of bits from stream, return 0s intead of continuing
return 0;
}
k = j->code_buffer;
j->code_buffer <<= 1;
--j->code_bits;
return k & 0x80000000;
}
// given a value that's at position X in the zigzag stream,
// where does it appear in the 8x8 matrix coded as row-major?
static const unsigned char stbi__jpeg_dezigzag[64 + 15] = {
0, 1, 8, 16, 9, 2, 3, 10, 17, 24, 32, 25, 18, 11, 4, 5, 12, 19, 26, 33, 40,
48, 41, 34, 27, 20, 13, 6, 7, 14, 21, 28, 35, 42, 49, 56, 57, 50, 43, 36,
29, 22, 15, 23, 30, 37, 44, 51, 58, 59, 52, 45, 38, 31, 39, 46, 53, 60, 61,
54, 47, 55, 62, 63,
// let corrupt input sample past end
63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63};
// decode one 64-entry block
static int stbi__jpeg_decode_block(stbi__jpeg *j, short data[64],
stbi__huffman *hdc, stbi__huffman *hac,
int16_t *fac, int b, uint16_t *dequant) {
unsigned int zig;
int diff, dc, k, t, c, r, s, rs;
if (j->code_bits < 16) stbi__grow_buffer_unsafe(j);
t = stbi__jpeg_huff_decode(j, hdc);
if (t < 0 || t > 15) return stbi__err("bad huffman code", "Corrupt JPEG");
// 0 all the ac values now so we can do it 32-bits at a time
bzero(data, 64 * sizeof(data[0]));
diff = t ? stbi__extend_receive(j, t) : 0;
if (!stbi__addints_valid(j->img_comp[b].dc_pred, diff)) {
return stbi__err("bad delta", "Corrupt JPEG");
}
dc = j->img_comp[b].dc_pred + diff;
j->img_comp[b].dc_pred = dc;
if (!stbi__mul2shorts_valid(dc, dequant[0])) {
return stbi__err("can't merge dc and ac", "Corrupt JPEG");
}
data[0] = (short)(dc * dequant[0]);
// decode AC components, see JPEG spec
k = 1;
do {
if (j->code_bits < 16) stbi__grow_buffer_unsafe(j);
c = (j->code_buffer >> (32 - FAST_BITS)) & ((1 << FAST_BITS) - 1);
r = fac[c];
if (r) { // fast-AC path
k += (r >> 4) & 15; // run
s = r & 15; // combined length
if (s > j->code_bits) {
return stbi__err("bad huffman code",
"Combined length longer than code bits available");
}
j->code_buffer <<= s;
j->code_bits -= s;
// decode into unzigzag'd location
zig = stbi__jpeg_dezigzag[k++];
data[zig] = (short)((r >> 8) * dequant[zig]);
} else {
rs = stbi__jpeg_huff_decode(j, hac);
if (rs < 0) return stbi__err("bad huffman code", "Corrupt JPEG");
s = rs & 15;
r = rs >> 4;
if (s == 0) {
if (rs != 0xf0) break; // end block
k += 16;
} else {
k += r;
// decode into unzigzag'd location
zig = stbi__jpeg_dezigzag[k++];
data[zig] = (short)(stbi__extend_receive(j, s) * dequant[zig]);
}
}
} while (k < 64);
return 1;
}
static int stbi__jpeg_decode_block_prog_dc(stbi__jpeg *j, short data[64],
stbi__huffman *hdc, int b) {
int t;
int diff, dc;
if (j->spec_end != 0) {
return stbi__err("can't merge dc and ac", "Corrupt JPEG");
}
if (j->code_bits < 16) stbi__grow_buffer_unsafe(j);
if (j->succ_high == 0) {
// first scan for DC coefficient, must be first
bzero(data, 64 * sizeof(data[0])); // 0 all the ac values now
t = stbi__jpeg_huff_decode(j, hdc);
if (t < 0 || t > 15) {
return stbi__err("can't merge dc and ac", "Corrupt JPEG");
}
diff = t ? stbi__extend_receive(j, t) : 0;
if (!stbi__addints_valid(j->img_comp[b].dc_pred, diff)) {
return stbi__err("bad delta", "Corrupt JPEG");
}
dc = j->img_comp[b].dc_pred + diff;
j->img_comp[b].dc_pred = dc;
if (!stbi__mul2shorts_valid(dc, 1 << j->succ_low)) {
return stbi__err("can't merge dc and ac", "Corrupt JPEG");
}
data[0] = (short)(dc * (1u << j->succ_low));
} else {
// refinement scan for DC coefficient
if (stbi__jpeg_get_bit(j)) data[0] += (short)(1u << j->succ_low);
}
return 1;
}
// @OPTIMIZE: store non-zigzagged during the decode passes,
// and only de-zigzag when dequantizing
static int stbi__jpeg_decode_block_prog_ac(stbi__jpeg *j, short data[64],
stbi__huffman *hac, int16_t *fac) {
short bit;
unsigned zig;
int k, c, r, s, rs, shift;
if (j->spec_start == 0) {
return stbi__err("can't merge dc and ac", "Corrupt JPEG");
}
if (j->succ_high == 0) {
shift = j->succ_low;
if (j->eob_run) {
--j->eob_run;
return 1;
}
k = j->spec_start;
do {
if (j->code_bits < 16) stbi__grow_buffer_unsafe(j);
c = (j->code_buffer >> (32 - FAST_BITS)) & ((1 << FAST_BITS) - 1);
r = fac[c];
if (r) { // fast-AC path
k += (r >> 4) & 15; // run
s = r & 15; // combined length
if (s > j->code_bits) {
return stbi__err("bad huffman code",
"Combined length longer than code bits available");
}
j->code_buffer <<= s;
j->code_bits -= s;
zig = stbi__jpeg_dezigzag[k++];
data[zig] = (short)((r >> 8) * (1u << shift));
} else {
rs = stbi__jpeg_huff_decode(j, hac);
if (rs < 0) return stbi__err("bad huffman code", "Corrupt JPEG");
s = rs & 15;
r = rs >> 4;
if (s == 0) {
if (r < 15) {
j->eob_run = (1 << r);
if (r) j->eob_run += stbi__jpeg_get_bits(j, r);
--j->eob_run;
break;
}
k += 16;
} else {
k += r;
zig = stbi__jpeg_dezigzag[k++];
data[zig] = (short)(stbi__extend_receive(j, s) * (1u << shift));
}
}
} while (k <= j->spec_end);
} else {
// refinement scan for these AC coefficients
bit = (short)(1u << j->succ_low);
if (j->eob_run) {
--j->eob_run;
for (k = j->spec_start; k <= j->spec_end; ++k) {
short *p = &data[stbi__jpeg_dezigzag[k]];
if (*p != 0)
if (stbi__jpeg_get_bit(j))
if ((*p & bit) == 0) {
if (*p > 0)
*p += bit;
else
*p -= bit;
}
}
} else {
k = j->spec_start;
do {
rs = stbi__jpeg_huff_decode(j, hac);
if (rs < 0) return stbi__err("bad huffman code", "Corrupt JPEG");
s = rs & 15;
r = rs >> 4;
if (s == 0) {
if (r < 15) {
j->eob_run = (1 << r) - 1;
if (r) j->eob_run += stbi__jpeg_get_bits(j, r);
r = 64; // force end of block
} else {
// r=15 s=0 should write 16 0s, so we just do
// a run of 15 0s and then write s (which is 0),
// so we don't have to do anything special here
}
} else {
if (s != 1) return stbi__err("bad huffman code", "Corrupt JPEG");
// sign bit
if (stbi__jpeg_get_bit(j)) {
s = bit;
} else {
s = -bit;
}
}
// advance by r
while (k <= j->spec_end) {
short *p = &data[stbi__jpeg_dezigzag[k++]];
if (*p != 0) {
if (stbi__jpeg_get_bit(j))
if ((*p & bit) == 0) {
if (*p > 0)
*p += bit;
else
*p -= bit;
}
} else {
if (r == 0) {
*p = (short)s;
break;
}
--r;
}
}
} while (k <= j->spec_end);
}
}
return 1;
}
// take a -128..127 value and stbi__clamp it and convert to 0..255
forceinline unsigned char stbi__clamp(int x) {
// trick to use a single test to catch both cases
if ((unsigned int)x > 255) {
if (x < 0) return 0;
if (x > 255) return 255;
}
return (unsigned char)x;
}
#define stbi__f2f(x) ((int)(((x)*4096 + 0.5)))
#define stbi__fsh(x) ((x)*4096)
// derived from jidctint -- DCT_ISLOW
#define STBI__IDCT_1D(s0, s1, s2, s3, s4, s5, s6, s7) \
int t0, t1, t2, t3, p1, p2, p3, p4, p5, x0, x1, x2, x3; \
p2 = s2; \
p3 = s6; \
p1 = (p2 + p3) * stbi__f2f(0.5411961f); \
t2 = p1 + p3 * stbi__f2f(-1.847759065f); \
t3 = p1 + p2 * stbi__f2f(0.765366865f); \
p2 = s0; \
p3 = s4; \
t0 = stbi__fsh(p2 + p3); \
t1 = stbi__fsh(p2 - p3); \
x0 = t0 + t3; \
x3 = t0 - t3; \
x1 = t1 + t2; \
x2 = t1 - t2; \
t0 = s7; \
t1 = s5; \
t2 = s3; \
t3 = s1; \
p3 = t0 + t2; \
p4 = t1 + t3; \
p1 = t0 + t3; \
p2 = t1 + t2; \
p5 = (p3 + p4) * stbi__f2f(1.175875602f); \
t0 = t0 * stbi__f2f(0.298631336f); \
t1 = t1 * stbi__f2f(2.053119869f); \
t2 = t2 * stbi__f2f(3.072711026f); \
t3 = t3 * stbi__f2f(1.501321110f); \
p1 = p5 + p1 * stbi__f2f(-0.899976223f); \
p2 = p5 + p2 * stbi__f2f(-2.562915447f); \
p3 = p3 * stbi__f2f(-1.961570560f); \
p4 = p4 * stbi__f2f(-0.390180644f); \
t3 += p1 + p4; \
t2 += p2 + p3; \
t1 += p2 + p4; \
t0 += p1 + p3;
static void stbi__idct_block(unsigned char *out, int out_stride,
short data[64]) {
int i, val[64], *v = val;
unsigned char *o;
short *d = data;
// columns
for (i = 0; i < 8; ++i, ++d, ++v) {
// if all zeroes, shortcut -- this avoids dequantizing 0s and IDCTing
if (d[8] == 0 && d[16] == 0 && d[24] == 0 && d[32] == 0 && d[40] == 0 &&
d[48] == 0 && d[56] == 0) {
// no shortcut 0 seconds
// (1|2|3|4|5|6|7)==0 0 seconds
// all separate -0.047 seconds
// 1 && 2|3 && 4|5 && 6|7: -0.047 seconds
int dcterm = d[0] * 4;
v[0] = v[8] = v[16] = v[24] = v[32] = v[40] = v[48] = v[56] = dcterm;
} else {
STBI__IDCT_1D(d[0], d[8], d[16], d[24], d[32], d[40], d[48], d[56])
// constants scaled things up by 1<<12; let's bring them back
// down, but keep 2 extra bits of precision
x0 += 512;
x1 += 512;
x2 += 512;
x3 += 512;
v[0] = (x0 + t3) >> 10;
v[56] = (x0 - t3) >> 10;
v[8] = (x1 + t2) >> 10;
v[48] = (x1 - t2) >> 10;
v[16] = (x2 + t1) >> 10;
v[40] = (x2 - t1) >> 10;
v[24] = (x3 + t0) >> 10;
v[32] = (x3 - t0) >> 10;
}
}
for (i = 0, v = val, o = out; i < 8; ++i, v += 8, o += out_stride) {
// no fast case since the first 1D IDCT spread components out
STBI__IDCT_1D(v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7])
// constants scaled things up by 1<<12, plus we had 1<<2 from first
// loop, plus horizontal and vertical each scale by sqrt(8) so together
// we've got an extra 1<<3, so 1<<17 total we need to remove.
// so we want to round that, which means adding 0.5 * 1<<17,
// aka 65536. Also, we'll end up with -128 to 127 that we want
// to encode as 0..255 by adding 128, so we'll add that before the shift
x0 += 65536 + (128 << 17);
x1 += 65536 + (128 << 17);
x2 += 65536 + (128 << 17);
x3 += 65536 + (128 << 17);
// tried computing the shifts into temps, or'ing the temps to see
// if any were out of range, but that was slower
o[0] = stbi__clamp((x0 + t3) >> 17);
o[7] = stbi__clamp((x0 - t3) >> 17);
o[1] = stbi__clamp((x1 + t2) >> 17);
o[6] = stbi__clamp((x1 - t2) >> 17);
o[2] = stbi__clamp((x2 + t1) >> 17);
o[5] = stbi__clamp((x2 - t1) >> 17);
o[3] = stbi__clamp((x3 + t0) >> 17);
o[4] = stbi__clamp((x3 - t0) >> 17);
}
}
#ifdef STBI_SSE2
// sse2 integer IDCT. not the fastest possible implementation but it
// produces bit-identical results to the generic C version so it's
// fully "transparent".
static void stbi__idct_simd(unsigned char *out, int out_stride,
short data[64]) {
// This is constructed to match our regular (generic) integer IDCT exactly.
__m128i row0, row1, row2, row3, row4, row5, row6, row7;
__m128i tmp;
// dot product constant: even elems=x, odd elems=y
#define dct_const(x, y) _mm_setr_epi16((x), (y), (x), (y), (x), (y), (x), (y))
// out(0) = c0[even]*x + c0[odd]*y (c0, x, y 16-bit, out 32-bit)
// out(1) = c1[even]*x + c1[odd]*y
#define dct_rot(out0, out1, x, y, c0, c1) \
__m128i c0##lo = _mm_unpacklo_epi16((x), (y)); \
__m128i c0##hi = _mm_unpackhi_epi16((x), (y)); \
__m128i out0##_l = _mm_madd_epi16(c0##lo, c0); \
__m128i out0##_h = _mm_madd_epi16(c0##hi, c0); \
__m128i out1##_l = _mm_madd_epi16(c0##lo, c1); \
__m128i out1##_h = _mm_madd_epi16(c0##hi, c1)
// out = in << 12 (in 16-bit, out 32-bit)
#define dct_widen(out, in) \
__m128i out##_l = \
_mm_srai_epi32(_mm_unpacklo_epi16(_mm_setzero_si128(), (in)), 4); \
__m128i out##_h = \
_mm_srai_epi32(_mm_unpackhi_epi16(_mm_setzero_si128(), (in)), 4)
// wide add
#define dct_wadd(out, a, b) \
__m128i out##_l = _mm_add_epi32(a##_l, b##_l); \
__m128i out##_h = _mm_add_epi32(a##_h, b##_h)
// wide sub
#define dct_wsub(out, a, b) \
__m128i out##_l = _mm_sub_epi32(a##_l, b##_l); \
__m128i out##_h = _mm_sub_epi32(a##_h, b##_h)
// butterfly a/b, add bias, then shift by "s" and pack
#define dct_bfly32o(out0, out1, a, b, bias, s) \
{ \
__m128i abiased_l = _mm_add_epi32(a##_l, bias); \
__m128i abiased_h = _mm_add_epi32(a##_h, bias); \
dct_wadd(sum, abiased, b); \
dct_wsub(dif, abiased, b); \
out0 = \
_mm_packs_epi32(_mm_srai_epi32(sum_l, s), _mm_srai_epi32(sum_h, s)); \
out1 = \
_mm_packs_epi32(_mm_srai_epi32(dif_l, s), _mm_srai_epi32(dif_h, s)); \
}
// 8-bit interleave step (for transposes)
#define dct_interleave8(a, b) \
tmp = a; \
a = _mm_unpacklo_epi8(a, b); \
b = _mm_unpackhi_epi8(tmp, b)
// 16-bit interleave step (for transposes)
#define dct_interleave16(a, b) \
tmp = a; \
a = _mm_unpacklo_epi16(a, b); \
b = _mm_unpackhi_epi16(tmp, b)
#define dct_pass(bias, shift) \
{ \
/* even part */ \
dct_rot(t2e, t3e, row2, row6, rot0_0, rot0_1); \
__m128i sum04 = _mm_add_epi16(row0, row4); \
__m128i dif04 = _mm_sub_epi16(row0, row4); \
dct_widen(t0e, sum04); \
dct_widen(t1e, dif04); \
dct_wadd(x0, t0e, t3e); \
dct_wsub(x3, t0e, t3e); \
dct_wadd(x1, t1e, t2e); \
dct_wsub(x2, t1e, t2e); \
/* odd part */ \
dct_rot(y0o, y2o, row7, row3, rot2_0, rot2_1); \
dct_rot(y1o, y3o, row5, row1, rot3_0, rot3_1); \
__m128i sum17 = _mm_add_epi16(row1, row7); \
__m128i sum35 = _mm_add_epi16(row3, row5); \
dct_rot(y4o, y5o, sum17, sum35, rot1_0, rot1_1); \
dct_wadd(x4, y0o, y4o); \
dct_wadd(x5, y1o, y5o); \
dct_wadd(x6, y2o, y5o); \
dct_wadd(x7, y3o, y4o); \
dct_bfly32o(row0, row7, x0, x7, bias, shift); \
dct_bfly32o(row1, row6, x1, x6, bias, shift); \
dct_bfly32o(row2, row5, x2, x5, bias, shift); \
dct_bfly32o(row3, row4, x3, x4, bias, shift); \
}
__m128i rot0_0 = dct_const(stbi__f2f(0.5411961f),
stbi__f2f(0.5411961f) + stbi__f2f(-1.847759065f));
__m128i rot0_1 = dct_const(stbi__f2f(0.5411961f) + stbi__f2f(0.765366865f),
stbi__f2f(0.5411961f));
__m128i rot1_0 = dct_const(stbi__f2f(1.175875602f) + stbi__f2f(-0.899976223f),
stbi__f2f(1.175875602f));
__m128i rot1_1 =
dct_const(stbi__f2f(1.175875602f),
stbi__f2f(1.175875602f) + stbi__f2f(-2.562915447f));
__m128i rot2_0 = dct_const(stbi__f2f(-1.961570560f) + stbi__f2f(0.298631336f),
stbi__f2f(-1.961570560f));
__m128i rot2_1 =
dct_const(stbi__f2f(-1.961570560f),
stbi__f2f(-1.961570560f) + stbi__f2f(3.072711026f));
__m128i rot3_0 = dct_const(stbi__f2f(-0.390180644f) + stbi__f2f(2.053119869f),
stbi__f2f(-0.390180644f));
__m128i rot3_1 =
dct_const(stbi__f2f(-0.390180644f),
stbi__f2f(-0.390180644f) + stbi__f2f(1.501321110f));
// rounding biases in column/row passes, see stbi__idct_block for explanation.
__m128i bias_0 = _mm_set1_epi32(512);
__m128i bias_1 = _mm_set1_epi32(65536 + (128 << 17));
// load
row0 = _mm_load_si128((const __m128i *)(data + 0 * 8));
row1 = _mm_load_si128((const __m128i *)(data + 1 * 8));
row2 = _mm_load_si128((const __m128i *)(data + 2 * 8));
row3 = _mm_load_si128((const __m128i *)(data + 3 * 8));
row4 = _mm_load_si128((const __m128i *)(data + 4 * 8));
row5 = _mm_load_si128((const __m128i *)(data + 5 * 8));
row6 = _mm_load_si128((const __m128i *)(data + 6 * 8));
row7 = _mm_load_si128((const __m128i *)(data + 7 * 8));
// column pass
dct_pass(bias_0, 10);
{
// 16bit 8x8 transpose pass 1
dct_interleave16(row0, row4);
dct_interleave16(row1, row5);
dct_interleave16(row2, row6);
dct_interleave16(row3, row7);
// transpose pass 2
dct_interleave16(row0, row2);
dct_interleave16(row1, row3);
dct_interleave16(row4, row6);
dct_interleave16(row5, row7);
// transpose pass 3
dct_interleave16(row0, row1);
dct_interleave16(row2, row3);
dct_interleave16(row4, row5);
dct_interleave16(row6, row7);
}
// row pass
dct_pass(bias_1, 17);
{
// pack
__m128i p0 = _mm_packus_epi16(row0, row1); // a0a1a2a3...a7b0b1b2b3...b7
__m128i p1 = _mm_packus_epi16(row2, row3);
__m128i p2 = _mm_packus_epi16(row4, row5);
__m128i p3 = _mm_packus_epi16(row6, row7);
// 8bit 8x8 transpose pass 1
dct_interleave8(p0, p2); // a0e0a1e1...
dct_interleave8(p1, p3); // c0g0c1g1...
// transpose pass 2
dct_interleave8(p0, p1); // a0c0e0g0...
dct_interleave8(p2, p3); // b0d0f0h0...
// transpose pass 3
dct_interleave8(p0, p2); // a0b0c0d0...
dct_interleave8(p1, p3); // a4b4c4d4...
// store
_mm_storel_epi64((__m128i *)out, p0);
out += out_stride;
_mm_storel_epi64((__m128i *)out, _mm_shuffle_epi32(p0, 0x4e));
out += out_stride;
_mm_storel_epi64((__m128i *)out, p2);
out += out_stride;
_mm_storel_epi64((__m128i *)out, _mm_shuffle_epi32(p2, 0x4e));
out += out_stride;
_mm_storel_epi64((__m128i *)out, p1);
out += out_stride;
_mm_storel_epi64((__m128i *)out, _mm_shuffle_epi32(p1, 0x4e));
out += out_stride;
_mm_storel_epi64((__m128i *)out, p3);
out += out_stride;
_mm_storel_epi64((__m128i *)out, _mm_shuffle_epi32(p3, 0x4e));
}
#undef dct_const
#undef dct_rot
#undef dct_widen
#undef dct_wadd
#undef dct_wsub
#undef dct_bfly32o
#undef dct_interleave8
#undef dct_interleave16
#undef dct_pass
}
#endif // STBI_SSE2
#ifdef STBI_NEON
// NEON integer IDCT. should produce bit-identical
// results to the generic C version.
static void stbi__idct_simd(unsigned char *out, int out_stride,
short data[64]) {
int16x8_t row0, row1, row2, row3, row4, row5, row6, row7;
int16x4_t rot0_0 = vdup_n_s16(stbi__f2f(0.5411961f));
int16x4_t rot0_1 = vdup_n_s16(stbi__f2f(-1.847759065f));
int16x4_t rot0_2 = vdup_n_s16(stbi__f2f(0.765366865f));
int16x4_t rot1_0 = vdup_n_s16(stbi__f2f(1.175875602f));
int16x4_t rot1_1 = vdup_n_s16(stbi__f2f(-0.899976223f));
int16x4_t rot1_2 = vdup_n_s16(stbi__f2f(-2.562915447f));
int16x4_t rot2_0 = vdup_n_s16(stbi__f2f(-1.961570560f));
int16x4_t rot2_1 = vdup_n_s16(stbi__f2f(-0.390180644f));
int16x4_t rot3_0 = vdup_n_s16(stbi__f2f(0.298631336f));
int16x4_t rot3_1 = vdup_n_s16(stbi__f2f(2.053119869f));
int16x4_t rot3_2 = vdup_n_s16(stbi__f2f(3.072711026f));
int16x4_t rot3_3 = vdup_n_s16(stbi__f2f(1.501321110f));
#define dct_long_mul(out, inq, coeff) \
int32x4_t out##_l = vmull_s16(vget_low_s16(inq), coeff); \
int32x4_t out##_h = vmull_s16(vget_high_s16(inq), coeff)
#define dct_long_mac(out, acc, inq, coeff) \
int32x4_t out##_l = vmlal_s16(acc##_l, vget_low_s16(inq), coeff); \
int32x4_t out##_h = vmlal_s16(acc##_h, vget_high_s16(inq), coeff)
#define dct_widen(out, inq) \
int32x4_t out##_l = vshll_n_s16(vget_low_s16(inq), 12); \
int32x4_t out##_h = vshll_n_s16(vget_high_s16(inq), 12)
// wide add
#define dct_wadd(out, a, b) \
int32x4_t out##_l = vaddq_s32(a##_l, b##_l); \
int32x4_t out##_h = vaddq_s32(a##_h, b##_h)
// wide sub
#define dct_wsub(out, a, b) \
int32x4_t out##_l = vsubq_s32(a##_l, b##_l); \
int32x4_t out##_h = vsubq_s32(a##_h, b##_h)
// butterfly a/b, then shift using "shiftop" by "s" and pack
#define dct_bfly32o(out0, out1, a, b, shiftop, s) \
{ \
dct_wadd(sum, a, b); \
dct_wsub(dif, a, b); \
out0 = vcombine_s16(shiftop(sum_l, s), shiftop(sum_h, s)); \
out1 = vcombine_s16(shiftop(dif_l, s), shiftop(dif_h, s)); \
}
#define dct_pass(shiftop, shift) \
{ \
/* even part */ \
int16x8_t sum26 = vaddq_s16(row2, row6); \
dct_long_mul(p1e, sum26, rot0_0); \
dct_long_mac(t2e, p1e, row6, rot0_1); \
dct_long_mac(t3e, p1e, row2, rot0_2); \
int16x8_t sum04 = vaddq_s16(row0, row4); \
int16x8_t dif04 = vsubq_s16(row0, row4); \
dct_widen(t0e, sum04); \
dct_widen(t1e, dif04); \
dct_wadd(x0, t0e, t3e); \
dct_wsub(x3, t0e, t3e); \
dct_wadd(x1, t1e, t2e); \
dct_wsub(x2, t1e, t2e); \
/* odd part */ \
int16x8_t sum15 = vaddq_s16(row1, row5); \
int16x8_t sum17 = vaddq_s16(row1, row7); \
int16x8_t sum35 = vaddq_s16(row3, row5); \
int16x8_t sum37 = vaddq_s16(row3, row7); \
int16x8_t sumodd = vaddq_s16(sum17, sum35); \
dct_long_mul(p5o, sumodd, rot1_0); \
dct_long_mac(p1o, p5o, sum17, rot1_1); \
dct_long_mac(p2o, p5o, sum35, rot1_2); \
dct_long_mul(p3o, sum37, rot2_0); \
dct_long_mul(p4o, sum15, rot2_1); \
dct_wadd(sump13o, p1o, p3o); \
dct_wadd(sump24o, p2o, p4o); \
dct_wadd(sump23o, p2o, p3o); \
dct_wadd(sump14o, p1o, p4o); \
dct_long_mac(x4, sump13o, row7, rot3_0); \
dct_long_mac(x5, sump24o, row5, rot3_1); \
dct_long_mac(x6, sump23o, row3, rot3_2); \
dct_long_mac(x7, sump14o, row1, rot3_3); \
dct_bfly32o(row0, row7, x0, x7, shiftop, shift); \
dct_bfly32o(row1, row6, x1, x6, shiftop, shift); \
dct_bfly32o(row2, row5, x2, x5, shiftop, shift); \
dct_bfly32o(row3, row4, x3, x4, shiftop, shift); \
}
// load
row0 = vld1q_s16(data + 0 * 8);
row1 = vld1q_s16(data + 1 * 8);
row2 = vld1q_s16(data + 2 * 8);
row3 = vld1q_s16(data + 3 * 8);
row4 = vld1q_s16(data + 4 * 8);
row5 = vld1q_s16(data + 5 * 8);
row6 = vld1q_s16(data + 6 * 8);
row7 = vld1q_s16(data + 7 * 8);
// add DC bias
row0 = vaddq_s16(row0, vsetq_lane_s16(1024, vdupq_n_s16(0), 0));
// column pass
dct_pass(vrshrn_n_s32, 10);
// 16bit 8x8 transpose
{
// these three map to a single VTRN.16, VTRN.32, and VSWP, respectively.
// whether compilers actually get this is another story, sadly.
#define dct_trn16(x, y) \
{ \
int16x8x2_t t = vtrnq_s16(x, y); \
x = t.val[0]; \
y = t.val[1]; \
}
#define dct_trn32(x, y) \
{ \
int32x4x2_t t = \
vtrnq_s32(vreinterpretq_s32_s16(x), vreinterpretq_s32_s16(y)); \
x = vreinterpretq_s16_s32(t.val[0]); \
y = vreinterpretq_s16_s32(t.val[1]); \
}
#define dct_trn64(x, y) \
{ \
int16x8_t x0 = x; \
int16x8_t y0 = y; \
x = vcombine_s16(vget_low_s16(x0), vget_low_s16(y0)); \
y = vcombine_s16(vget_high_s16(x0), vget_high_s16(y0)); \
}
// pass 1
dct_trn16(row0, row1); // a0b0a2b2a4b4a6b6
dct_trn16(row2, row3);
dct_trn16(row4, row5);
dct_trn16(row6, row7);
// pass 2
dct_trn32(row0, row2); // a0b0c0d0a4b4c4d4
dct_trn32(row1, row3);
dct_trn32(row4, row6);
dct_trn32(row5, row7);
// pass 3
dct_trn64(row0, row4); // a0b0c0d0e0f0g0h0
dct_trn64(row1, row5);
dct_trn64(row2, row6);
dct_trn64(row3, row7);
#undef dct_trn16
#undef dct_trn32
#undef dct_trn64
}
// row pass
// vrshrn_n_s32 only supports shifts up to 16, we need
// 17. so do a non-rounding shift of 16 first then follow
// up with a rounding shift by 1.
dct_pass(vshrn_n_s32, 16);
{
// pack and round
uint8x8_t p0 = vqrshrun_n_s16(row0, 1);
uint8x8_t p1 = vqrshrun_n_s16(row1, 1);
uint8x8_t p2 = vqrshrun_n_s16(row2, 1);
uint8x8_t p3 = vqrshrun_n_s16(row3, 1);
uint8x8_t p4 = vqrshrun_n_s16(row4, 1);
uint8x8_t p5 = vqrshrun_n_s16(row5, 1);
uint8x8_t p6 = vqrshrun_n_s16(row6, 1);
uint8x8_t p7 = vqrshrun_n_s16(row7, 1);
// again, these can translate into one instruction, but often don't.
#define dct_trn8_8(x, y) \
{ \
uint8x8x2_t t = vtrn_u8(x, y); \
x = t.val[0]; \
y = t.val[1]; \
}
#define dct_trn8_16(x, y) \
{ \
uint16x4x2_t t = vtrn_u16(vreinterpret_u16_u8(x), vreinterpret_u16_u8(y)); \
x = vreinterpret_u8_u16(t.val[0]); \
y = vreinterpret_u8_u16(t.val[1]); \
}
#define dct_trn8_32(x, y) \
{ \
uint32x2x2_t t = vtrn_u32(vreinterpret_u32_u8(x), vreinterpret_u32_u8(y)); \
x = vreinterpret_u8_u32(t.val[0]); \
y = vreinterpret_u8_u32(t.val[1]); \
}
// sadly can't use interleaved stores here since we only write
// 8 bytes to each scan line!
// 8x8 8-bit transpose pass 1
dct_trn8_8(p0, p1);
dct_trn8_8(p2, p3);
dct_trn8_8(p4, p5);
dct_trn8_8(p6, p7);
// pass 2
dct_trn8_16(p0, p2);
dct_trn8_16(p1, p3);
dct_trn8_16(p4, p6);
dct_trn8_16(p5, p7);
// pass 3
dct_trn8_32(p0, p4);
dct_trn8_32(p1, p5);
dct_trn8_32(p2, p6);
dct_trn8_32(p3, p7);
// store
vst1_u8(out, p0);
out += out_stride;
vst1_u8(out, p1);
out += out_stride;
vst1_u8(out, p2);
out += out_stride;
vst1_u8(out, p3);
out += out_stride;
vst1_u8(out, p4);
out += out_stride;
vst1_u8(out, p5);
out += out_stride;
vst1_u8(out, p6);
out += out_stride;
vst1_u8(out, p7);
#undef dct_trn8_8
#undef dct_trn8_16
#undef dct_trn8_32
}
#undef dct_long_mul
#undef dct_long_mac
#undef dct_widen
#undef dct_wadd
#undef dct_wsub
#undef dct_bfly32o
#undef dct_pass
}
#endif // STBI_NEON
#define STBI__MARKER_none 0xff
// if there's a pending marker from the entropy stream, return that
// otherwise, fetch from the stream and get a marker. if there's no
// marker, return 0xff, which is never a valid marker value
static unsigned char stbi__get_marker(stbi__jpeg *j) {
unsigned char x;
if (j->marker != STBI__MARKER_none) {
x = j->marker;
j->marker = STBI__MARKER_none;
return x;
}
x = stbi__get8(j->s);
if (x != 0xff) return STBI__MARKER_none;
while (x == 0xff) x = stbi__get8(j->s); // consume repeated 0xff fill bytes
return x;
}
// in each scan, we'll have scan_n components, and the order
// of the components is specified by order[]
#define STBI__RESTART(x) ((x) >= 0xd0 && (x) <= 0xd7)
// after a restart interval, stbi__jpeg_reset the entropy decoder and
// the dc prediction
static void stbi__jpeg_reset(stbi__jpeg *j) {
j->code_bits = 0;
j->code_buffer = 0;
j->nomore = 0;
j->img_comp[0].dc_pred = j->img_comp[1].dc_pred = j->img_comp[2].dc_pred =
j->img_comp[3].dc_pred = 0;
j->marker = STBI__MARKER_none;
j->todo = j->restart_interval ? j->restart_interval : 0x7fffffff;
j->eob_run = 0;
// no more than 1<<31 MCUs if no restart_interal? that's plenty safe,
// since we don't even allow 1<<30 pixels
}
static int stbi__parse_entropy_coded_data(stbi__jpeg *z) {
stbi__jpeg_reset(z);
if (!z->progressive) {
if (z->scan_n == 1) {
int i, j;
short data[64] forcealign(16);
int n = z->order[0];
// non-interleaved data, we just need to process one block at a time,
// in trivial scanline order
// number of blocks to do just depends on how many actual "pixels" this
// component has, independent of interleaved MCU blocking and such
int w = (z->img_comp[n].x + 7) >> 3;
int h = (z->img_comp[n].y + 7) >> 3;
for (j = 0; j < h; ++j) {
for (i = 0; i < w; ++i) {
int ha = z->img_comp[n].ha;
if (!stbi__jpeg_decode_block(z, data, z->huff_dc + z->img_comp[n].hd,
z->huff_ac + ha, z->fast_ac[ha], n,
z->dequant[z->img_comp[n].tq]))
return 0;
idct_block_kernel(
z->img_comp[n].data + z->img_comp[n].w2 * j * 8 + i * 8,
z->img_comp[n].w2, data);
// every data block is an MCU, so countdown the restart interval
if (--z->todo <= 0) {
if (z->code_bits < 24) stbi__grow_buffer_unsafe(z);
// if it's NOT a restart, then just bail, so we get corrupt data
// rather than no data
if (!STBI__RESTART(z->marker)) return 1;
stbi__jpeg_reset(z);
}
}
}
return 1;
} else { // interleaved
int i, j, k, x, y;
short data[64] forcealign(16);
for (j = 0; j < z->img_mcu_y; ++j) {
for (i = 0; i < z->img_mcu_x; ++i) {
// scan an interleaved mcu... process scan_n components in order
for (k = 0; k < z->scan_n; ++k) {
int n = z->order[k];
// scan out an mcu's worth of this component; that's just determined
// by the basic H and V specified for the component
for (y = 0; y < z->img_comp[n].v; ++y) {
for (x = 0; x < z->img_comp[n].h; ++x) {
int x2 = (i * z->img_comp[n].h + x) * 8;
int y2 = (j * z->img_comp[n].v + y) * 8;
int ha = z->img_comp[n].ha;
if (!stbi__jpeg_decode_block(z, data,
z->huff_dc + z->img_comp[n].hd,
z->huff_ac + ha, z->fast_ac[ha], n,
z->dequant[z->img_comp[n].tq]))
return 0;
idct_block_kernel(
z->img_comp[n].data + z->img_comp[n].w2 * y2 + x2,
z->img_comp[n].w2, data);
}
}
}
// after all interleaved components, that's an interleaved MCU,
// so now count down the restart interval
if (--z->todo <= 0) {
if (z->code_bits < 24) stbi__grow_buffer_unsafe(z);
if (!STBI__RESTART(z->marker)) return 1;
stbi__jpeg_reset(z);
}
}
}
return 1;
}
} else {
if (z->scan_n == 1) {
int i, j;
int n = z->order[0];
// non-interleaved data, we just need to process one block at a time,
// in trivial scanline order
// number of blocks to do just depends on how many actual "pixels" this
// component has, independent of interleaved MCU blocking and such
int w = (z->img_comp[n].x + 7) >> 3;
int h = (z->img_comp[n].y + 7) >> 3;
for (j = 0; j < h; ++j) {
for (i = 0; i < w; ++i) {
short *data =
z->img_comp[n].coeff + 64 * (i + j * z->img_comp[n].coeff_w);
if (z->spec_start == 0) {
if (!stbi__jpeg_decode_block_prog_dc(
z, data, &z->huff_dc[z->img_comp[n].hd], n))
return 0;
} else {
int ha = z->img_comp[n].ha;
if (!stbi__jpeg_decode_block_prog_ac(z, data, &z->huff_ac[ha],
z->fast_ac[ha]))
return 0;
}
// every data block is an MCU, so countdown the restart interval
if (--z->todo <= 0) {
if (z->code_bits < 24) stbi__grow_buffer_unsafe(z);
if (!STBI__RESTART(z->marker)) return 1;
stbi__jpeg_reset(z);
}
}
}
return 1;
} else { // interleaved
int i, j, k, x, y;
for (j = 0; j < z->img_mcu_y; ++j) {
for (i = 0; i < z->img_mcu_x; ++i) {
// scan an interleaved mcu... process scan_n components in order
for (k = 0; k < z->scan_n; ++k) {
int n = z->order[k];
// scan out an mcu's worth of this component; that's just determined
// by the basic H and V specified for the component
for (y = 0; y < z->img_comp[n].v; ++y) {
for (x = 0; x < z->img_comp[n].h; ++x) {
int x2 = (i * z->img_comp[n].h + x);
int y2 = (j * z->img_comp[n].v + y);
short *data = z->img_comp[n].coeff +
64 * (x2 + y2 * z->img_comp[n].coeff_w);
if (!stbi__jpeg_decode_block_prog_dc(
z, data, &z->huff_dc[z->img_comp[n].hd], n))
return 0;
}
}
}
// after all interleaved components, that's an interleaved MCU,
// so now count down the restart interval
if (--z->todo <= 0) {
if (z->code_bits < 24) stbi__grow_buffer_unsafe(z);
if (!STBI__RESTART(z->marker)) return 1;
stbi__jpeg_reset(z);
}
}
}
return 1;
}
}
}
static void stbi__jpeg_dequantize(short *data, uint16_t *dequant) {
int i;
for (i = 0; i < 64; ++i) data[i] *= dequant[i];
}
static void stbi__jpeg_finish(stbi__jpeg *z) {
if (z->progressive) {
// dequantize and idct the data
int i, j, n;
for (n = 0; n < z->s->img_n; ++n) {
int w = (z->img_comp[n].x + 7) >> 3;
int h = (z->img_comp[n].y + 7) >> 3;
for (j = 0; j < h; ++j) {
for (i = 0; i < w; ++i) {
short *data =
z->img_comp[n].coeff + 64 * (i + j * z->img_comp[n].coeff_w);
stbi__jpeg_dequantize(data, z->dequant[z->img_comp[n].tq]);
idct_block_kernel(
z->img_comp[n].data + z->img_comp[n].w2 * j * 8 + i * 8,
z->img_comp[n].w2, data);
}
}
}
}
}
static int stbi__process_marker(stbi__jpeg *z, int m) {
int L;
switch (m) {
case STBI__MARKER_none: // no marker found
return stbi__err("expected marker", "Corrupt JPEG");
case 0xDD: // DRI - specify restart interval
if (stbi__get16be(z->s) != 4)
return stbi__err("bad DRI len", "Corrupt JPEG");
z->restart_interval = stbi__get16be(z->s);
return 1;
case 0xDB: // DQT - define quantization table
L = stbi__get16be(z->s) - 2;
while (L > 0) {
int q = stbi__get8(z->s);
int p = q >> 4, sixteen = (p != 0);
int t = q & 15, i;
if (p != 0 && p != 1) return stbi__err("bad DQT type", "Corrupt JPEG");
if (t > 3) return stbi__err("bad DQT table", "Corrupt JPEG");
for (i = 0; i < 64; ++i)
z->dequant[t][stbi__jpeg_dezigzag[i]] =
(uint16_t)(sixteen ? stbi__get16be(z->s) : stbi__get8(z->s));
L -= (sixteen ? 129 : 65);
}
return L == 0;
case 0xC4: // DHT - define huffman table
L = stbi__get16be(z->s) - 2;
while (L > 0) {
unsigned char *v;
int sizes[16], i, n = 0;
int q = stbi__get8(z->s);
int tc = q >> 4;
int th = q & 15;
if (tc > 1 || th > 3)
return stbi__err("bad DHT header", "Corrupt JPEG");
for (i = 0; i < 16; ++i) {
sizes[i] = stbi__get8(z->s);
n += sizes[i];
}
if (n > 256) {
// Loop over i < n would write past end of values!
return stbi__err("bad DHT header", "Corrupt JPEG");
}
L -= 17;
if (tc == 0) {
if (!stbi__build_huffman(z->huff_dc + th, sizes)) return 0;
v = z->huff_dc[th].values;
} else {
if (!stbi__build_huffman(z->huff_ac + th, sizes)) return 0;
v = z->huff_ac[th].values;
}
for (i = 0; i < n; ++i) v[i] = stbi__get8(z->s);
if (tc != 0) stbi__build_fast_ac(z->fast_ac[th], z->huff_ac + th);
L -= n;
}
return L == 0;
}
// check for comment block or APP blocks
if ((m >= 0xE0 && m <= 0xEF) || m == 0xFE) {
L = stbi__get16be(z->s);
if (L < 2) {
if (m == 0xFE)
return stbi__err("bad COM len", "Corrupt JPEG");
else
return stbi__err("bad APP len", "Corrupt JPEG");
}
L -= 2;
if (m == 0xE0 && L >= 5) { // JFIF APP0 segment
static const unsigned char tag[5] = {'J', 'F', 'I', 'F', '\0'};
int ok = 1;
int i;
for (i = 0; i < 5; ++i)
if (stbi__get8(z->s) != tag[i]) ok = 0;
L -= 5;
if (ok) z->jfif = m;
} else if (m == 0xEE && L >= 12) { // Adobe APP14 segment
static const unsigned char tag[6] = {'A', 'd', 'o', 'b', 'e', '\0'};
int ok = 1;
int i;
for (i = 0; i < 6; ++i)
if (stbi__get8(z->s) != tag[i]) ok = 0;
L -= 6;
if (ok) {
stbi__get8(z->s); // version
stbi__get16be(z->s); // flags0
stbi__get16be(z->s); // flags1
z->app14_color_transform = stbi__get8(z->s); // color transform
L -= 6;
}
}
stbi__skip(z->s, L);
return 1;
}
return stbi__err("unknown marker", "Corrupt JPEG");
}
// after we see SOS
static int stbi__process_scan_header(stbi__jpeg *z) {
int i;
int Ls = stbi__get16be(z->s);
z->scan_n = stbi__get8(z->s);
if (z->scan_n < 1 || z->scan_n > 4 || z->scan_n > (int)z->s->img_n)
return stbi__err("bad SOS component count", "Corrupt JPEG");
if (Ls != 6 + 2 * z->scan_n) return stbi__err("bad SOS len", "Corrupt JPEG");
for (i = 0; i < z->scan_n; ++i) {
int id = stbi__get8(z->s), which;
int q = stbi__get8(z->s);
for (which = 0; which < z->s->img_n; ++which)
if (z->img_comp[which].id == id) break;
if (which == z->s->img_n) return 0; // no match
z->img_comp[which].hd = q >> 4;
if (z->img_comp[which].hd > 3)
return stbi__err("bad DC huff", "Corrupt JPEG");
z->img_comp[which].ha = q & 15;
if (z->img_comp[which].ha > 3)
return stbi__err("bad AC huff", "Corrupt JPEG");
z->order[i] = which;
}
{
int aa;
z->spec_start = stbi__get8(z->s);
z->spec_end = stbi__get8(z->s); // should be 63, but might be 0
aa = stbi__get8(z->s);
z->succ_high = (aa >> 4);
z->succ_low = (aa & 15);
if (z->progressive) {
if (z->spec_start > 63 || z->spec_end > 63 ||
z->spec_start > z->spec_end || z->succ_high > 13 || z->succ_low > 13)
return stbi__err("bad SOS", "Corrupt JPEG");
} else {
if (z->spec_start != 0) return stbi__err("bad SOS", "Corrupt JPEG");
if (z->succ_high != 0 || z->succ_low != 0)
return stbi__err("bad SOS", "Corrupt JPEG");
z->spec_end = 63;
}
}
return 1;
}
static int stbi__free_jpeg_components(stbi__jpeg *z, int ncomp, int why) {
int i;
for (i = 0; i < ncomp; ++i) {
if (z->img_comp[i].data) {
free(z->img_comp[i].data);
z->img_comp[i].data = NULL;
}
if (z->img_comp[i].coeff) {
free(z->img_comp[i].coeff);
z->img_comp[i].coeff = NULL;
}
if (z->img_comp[i].linebuf) {
free(z->img_comp[i].linebuf);
z->img_comp[i].linebuf = NULL;
}
}
return why;
}
static int stbi__process_frame_header(stbi__jpeg *z, int scan) {
stbi__context *s = z->s;
int Lf, p, i, q, h_max = 1, v_max = 1, c;
Lf = stbi__get16be(s);
if (Lf < 11) {
// JPEG
return stbi__err("bad SOF len", "Corrupt JPEG");
}
p = stbi__get8(s);
if (p != 8) {
// JPEG baseline
return stbi__err("only 8-bit", "JPEG format not supported: 8-bit only");
}
s->img_y = stbi__get16be(s);
if (s->img_y == 0) {
// Legal, but we don't handle it--but neither does IJG
return stbi__err("no header height",
"JPEG format not supported: delayed height");
}
s->img_x = stbi__get16be(s);
if (s->img_x == 0) {
// JPEG requires
return stbi__err("0 width", "Corrupt JPEG");
}
if (s->img_y > STBI_MAX_DIMENSIONS) {
return stbi__err("too large", "Very large image (corrupt?)");
}
if (s->img_x > STBI_MAX_DIMENSIONS) {
return stbi__err("too large", "Very large image (corrupt?)");
}
c = stbi__get8(s);
if (c != 3 && c != 1 && c != 4) {
return stbi__err("bad component count", "Corrupt JPEG");
}
s->img_n = c;
for (i = 0; i < c; ++i) {
z->img_comp[i].data = NULL;
z->img_comp[i].linebuf = NULL;
}
if (Lf != 8 + 3 * s->img_n) return stbi__err("bad SOF len", "Corrupt JPEG");
z->rgb = 0;
for (i = 0; i < s->img_n; ++i) {
static const unsigned char rgb[3] = {'R', 'G', 'B'};
z->img_comp[i].id = stbi__get8(s);
if (s->img_n == 3 && z->img_comp[i].id == rgb[i]) ++z->rgb;
q = stbi__get8(s);
z->img_comp[i].h = (q >> 4);
if (!z->img_comp[i].h || z->img_comp[i].h > 4)
return stbi__err("bad H", "Corrupt JPEG");
z->img_comp[i].v = q & 15;
if (!z->img_comp[i].v || z->img_comp[i].v > 4)
return stbi__err("bad V", "Corrupt JPEG");
z->img_comp[i].tq = stbi__get8(s);
if (z->img_comp[i].tq > 3) return stbi__err("bad TQ", "Corrupt JPEG");
}
if (scan != STBI__SCAN_load) return 1;
if (!stbi__mad3sizes_valid(s->img_x, s->img_y, s->img_n, 0))
return stbi__err("too large", "Image too large to decode");
for (i = 0; i < s->img_n; ++i) {
if (z->img_comp[i].h > h_max) h_max = z->img_comp[i].h;
if (z->img_comp[i].v > v_max) v_max = z->img_comp[i].v;
}
// check that plane subsampling factors are integer ratios;
// our resamplers can't deal with fractional ratios
// and I've never seen a non-corrupted JPEG file actually use them
for (i = 0; i < s->img_n; ++i) {
if (h_max % z->img_comp[i].h != 0) {
return stbi__err("bad H", "Corrupt JPEG");
}
if (v_max % z->img_comp[i].v != 0) {
return stbi__err("bad V", "Corrupt JPEG");
}
}
// compute interleaved mcu info
z->img_h_max = h_max;
z->img_v_max = v_max;
z->img_mcu_w = h_max * 8;
z->img_mcu_h = v_max * 8;
// these sizes can't be more than 17 bits
z->img_mcu_x = (s->img_x + z->img_mcu_w - 1) / z->img_mcu_w;
z->img_mcu_y = (s->img_y + z->img_mcu_h - 1) / z->img_mcu_h;
for (i = 0; i < s->img_n; ++i) {
// number of effective pixels (e.g. for non-interleaved MCU)
z->img_comp[i].x = (s->img_x * z->img_comp[i].h + h_max - 1) / h_max;
z->img_comp[i].y = (s->img_y * z->img_comp[i].v + v_max - 1) / v_max;
// to simplify generation, we'll allocate enough memory to decode
// the bogus oversized data from using interleaved MCUs and their
// big blocks (e.g. a 16x16 iMCU on an image of width 33); we won't
// discard the extra data until colorspace conversion
//
// img_mcu_x, img_mcu_y: <=17 bits; comp[i].h and .v are <=4 (checked
// earlier) so these muls can't overflow with 32-bit ints (which we require)
z->img_comp[i].w2 = z->img_mcu_x * z->img_comp[i].h * 8;
z->img_comp[i].h2 = z->img_mcu_y * z->img_comp[i].v * 8;
z->img_comp[i].coeff = NULL;
z->img_comp[i].linebuf = NULL;
z->img_comp[i].data =
stbi__malloc_mad2(z->img_comp[i].w2, z->img_comp[i].h2, 15);
if (z->progressive) {
// w2, h2 are multiples of 8 (see above)
z->img_comp[i].coeff_w = z->img_comp[i].w2 / 8;
z->img_comp[i].coeff_h = z->img_comp[i].h2 / 8;
z->img_comp[i].coeff = stbi__malloc_mad3(
z->img_comp[i].w2, z->img_comp[i].h2, sizeof(short), 15);
}
}
return 1;
}
// use comparisons since in some cases we handle more than one case (e.g. SOF)
#define stbi__DNL(x) ((x) == 0xdc)
#define stbi__SOI(x) ((x) == 0xd8)
#define stbi__EOI(x) ((x) == 0xd9)
#define stbi__SOF(x) ((x) == 0xc0 || (x) == 0xc1 || (x) == 0xc2)
#define stbi__SOS(x) ((x) == 0xda)
#define stbi__SOF_progressive(x) ((x) == 0xc2)
static int stbi__decode_jpeg_header(stbi__jpeg *z, int scan) {
int m;
z->jfif = 0;
z->app14_color_transform = -1; // valid values are 0,1,2
z->marker = STBI__MARKER_none; // initialize cached marker to empty
m = stbi__get_marker(z);
if (!stbi__SOI(m)) return 0;
if (scan == STBI__SCAN_type) return 1;
m = stbi__get_marker(z);
while (!stbi__SOF(m)) {
if (!stbi__process_marker(z, m)) return 0;
m = stbi__get_marker(z);
while (m == STBI__MARKER_none) {
// some files have extra padding after their blocks, so ok, we'll scan
if (stbi__at_eof(z->s)) return stbi__err("no SOF", "Corrupt JPEG");
m = stbi__get_marker(z);
}
}
z->progressive = stbi__SOF_progressive(m);
if (!stbi__process_frame_header(z, scan)) return 0;
return 1;
}
static unsigned char stbi__skip_jpeg_junk_at_end(stbi__jpeg *j) {
// some JPEGs have junk at end, skip over it but if we find what looks
// like a valid marker, resume there
while (!stbi__at_eof(j->s)) {
unsigned char x = stbi__get8(j->s);
while (x == 0xff) { // might be a marker
if (stbi__at_eof(j->s)) return STBI__MARKER_none;
x = stbi__get8(j->s);
if (x != 0x00 && x != 0xff) {
// not a stuffed zero or lead-in to another marker, looks
// like an actual marker, return it
return x;
}
// stuffed zero has x=0 now which ends the loop, meaning we go
// back to regular scan loop.
// repeated 0xff keeps trying to read the next byte of the marker.
}
}
return STBI__MARKER_none;
}
// decode image to YCbCr format
static int stbi__decode_jpeg_image(stbi__jpeg *j) {
int m;
for (m = 0; m < 4; m++) {
j->img_comp[m].data = NULL;
j->img_comp[m].coeff = NULL;
}
j->restart_interval = 0;
if (!stbi__decode_jpeg_header(j, STBI__SCAN_load)) return 0;
m = stbi__get_marker(j);
while (!stbi__EOI(m)) {
if (stbi__SOS(m)) {
if (!stbi__process_scan_header(j)) return 0;
if (!stbi__parse_entropy_coded_data(j)) return 0;
if (j->marker == STBI__MARKER_none) {
j->marker = stbi__skip_jpeg_junk_at_end(j);
// if we reach eof without hitting a marker, stbi__get_marker() below
// will fail and we'll eventually return 0
}
m = stbi__get_marker(j);
if (STBI__RESTART(m)) m = stbi__get_marker(j);
} else if (stbi__DNL(m)) {
int Ld = stbi__get16be(j->s);
uint32_t NL = stbi__get16be(j->s);
if (Ld != 4) return stbi__err("bad DNL len", "Corrupt JPEG");
if (NL != j->s->img_y) return stbi__err("bad DNL height", "Corrupt JPEG");
m = stbi__get_marker(j);
} else {
if (!stbi__process_marker(j, m)) return 1;
m = stbi__get_marker(j);
}
}
if (j->progressive) stbi__jpeg_finish(j);
return 1;
}
// static jfif-centered resampling (across block boundaries)
typedef unsigned char *(*resample_row_func)(unsigned char *out,
unsigned char *in0,
unsigned char *in1, int w, int hs);
#define stbi__div4(x) ((unsigned char)((x) >> 2))
static unsigned char *resample_row_1(unsigned char *out, unsigned char *in_near,
unsigned char *in_far, int w, int hs) {
return in_near;
}
static unsigned char *stbi__resample_row_v_2(unsigned char *out,
unsigned char *in_near,
unsigned char *in_far, int w,
int hs) {
// need to generate two samples vertically for every one in input
int i;
for (i = 0; i < w; ++i) out[i] = stbi__div4(3 * in_near[i] + in_far[i] + 2);
return out;
}
static unsigned char *stbi__resample_row_h_2(unsigned char *out,
unsigned char *in_near,
unsigned char *in_far, int w,
int hs) {
// need to generate two samples horizontally for every one in input
int i;
unsigned char *input = in_near;
if (w == 1) {
// if only one sample, can't do any interpolation
out[0] = out[1] = input[0];
return out;
}
out[0] = input[0];
out[1] = stbi__div4(input[0] * 3 + input[1] + 2);
for (i = 1; i < w - 1; ++i) {
int n = 3 * input[i] + 2;
out[i * 2 + 0] = stbi__div4(n + input[i - 1]);
out[i * 2 + 1] = stbi__div4(n + input[i + 1]);
}
out[i * 2 + 0] = stbi__div4(input[w - 2] * 3 + input[w - 1] + 2);
out[i * 2 + 1] = input[w - 1];
return out;
}
#define stbi__div16(x) ((unsigned char)((x) >> 4))
static unsigned char *stbi__resample_row_hv_2(unsigned char *out,
unsigned char *in_near,
unsigned char *in_far, int w,
int hs) {
// need to generate 2x2 samples for every one in input
int i, t0, t1;
if (w == 1) {
out[0] = out[1] = stbi__div4(3 * in_near[0] + in_far[0] + 2);
return out;
}
t1 = 3 * in_near[0] + in_far[0];
out[0] = stbi__div4(t1 + 2);
for (i = 1; i < w; ++i) {
t0 = t1;
t1 = 3 * in_near[i] + in_far[i];
out[i * 2 - 1] = stbi__div16(3 * t0 + t1 + 8);
out[i * 2] = stbi__div16(3 * t1 + t0 + 8);
}
out[w * 2 - 1] = stbi__div4(t1 + 2);
return out;
}
#if defined(STBI_SSE2)
static unsigned char *stbi__resample_row_hv_2_simd(unsigned char *out,
unsigned char *in_near,
unsigned char *in_far, int w,
int hs) {
// need to generate 2x2 samples for every one in input
int i = 0, t0, t1;
if (w == 1) {
out[0] = out[1] = stbi__div4(3 * in_near[0] + in_far[0] + 2);
return out;
}
t1 = 3 * in_near[0] + in_far[0];
// process groups of 8 pixels for as long as we can.
// note we can't handle the last pixel in a row in this loop
// because we need to handle the filter boundary conditions.
for (; i < ((w - 1) & ~7); i += 8) {
// load and perform the vertical filtering pass
// this uses 3*x + y = 4*x + (y - x)
__m128i zero = _mm_setzero_si128();
__m128i farb = _mm_loadl_epi64((__m128i *)(in_far + i));
__m128i nearb = _mm_loadl_epi64((__m128i *)(in_near + i));
__m128i farw = _mm_unpacklo_epi8(farb, zero);
__m128i nearw = _mm_unpacklo_epi8(nearb, zero);
__m128i diff = _mm_sub_epi16(farw, nearw);
__m128i nears = _mm_slli_epi16(nearw, 2);
__m128i curr = _mm_add_epi16(nears, diff); // current row
// horizontal filter works the same based on shifted vers of current
// row. "prev" is current row shifted right by 1 pixel; we need to
// insert the previous pixel value (from t1).
// "next" is current row shifted left by 1 pixel, with first pixel
// of next block of 8 pixels added in.
__m128i prv0 = _mm_slli_si128(curr, 2);
__m128i nxt0 = _mm_srli_si128(curr, 2);
__m128i prev = _mm_insert_epi16(prv0, t1, 0);
__m128i next =
_mm_insert_epi16(nxt0, 3 * in_near[i + 8] + in_far[i + 8], 7);
// horizontal filter, polyphase implementation since it's convenient:
// even pixels = 3*cur + prev = cur*4 + (prev - cur)
// odd pixels = 3*cur + next = cur*4 + (next - cur)
// note the shared term.
__m128i bias = _mm_set1_epi16(8);
__m128i curs = _mm_slli_epi16(curr, 2);
__m128i prvd = _mm_sub_epi16(prev, curr);
__m128i nxtd = _mm_sub_epi16(next, curr);
__m128i curb = _mm_add_epi16(curs, bias);
__m128i even = _mm_add_epi16(prvd, curb);
__m128i odd = _mm_add_epi16(nxtd, curb);
// interleave even and odd pixels, then undo scaling.
__m128i int0 = _mm_unpacklo_epi16(even, odd);
__m128i int1 = _mm_unpackhi_epi16(even, odd);
__m128i de0 = _mm_srli_epi16(int0, 4);
__m128i de1 = _mm_srli_epi16(int1, 4);
// pack and write output
__m128i outv = _mm_packus_epi16(de0, de1);
_mm_storeu_si128((__m128i *)(out + i * 2), outv);
// "previous" value for next iter
t1 = 3 * in_near[i + 7] + in_far[i + 7];
}
t0 = t1;
t1 = 3 * in_near[i] + in_far[i];
out[i * 2] = stbi__div16(3 * t1 + t0 + 8);
for (++i; i < w; ++i) {
t0 = t1;
t1 = 3 * in_near[i] + in_far[i];
out[i * 2 - 1] = stbi__div16(3 * t0 + t1 + 8);
out[i * 2] = stbi__div16(3 * t1 + t0 + 8);
}
out[w * 2 - 1] = stbi__div4(t1 + 2);
return out;
}
#endif
static unsigned char *stbi__resample_row_nearest(unsigned char *out,
unsigned char *in_near,
unsigned char *in_far, int w,
int hs) {
int i, j;
for (i = 0; i < w; ++i) {
for (j = 0; j < hs; ++j) {
out[i * hs + j] = in_near[i];
}
}
return out;
}
// this is a reduced-precision calculation of YCbCr-to-RGB introduced
// to make sure the code produces the same results in both SIMD and scalar
#define stbi__float2fixed(x) (((int)((x)*4096.0f + 0.5f)) << 8)
static void stbi__YCbCr_to_RGB_row(unsigned char *out, const unsigned char *y,
const unsigned char *pcb,
const unsigned char *pcr, int count,
int step) {
int i;
for (i = 0; i < count; ++i) {
int y_fixed = (y[i] << 20) + (1 << 19); // rounding
int r, g, b;
int cr = pcr[i] - 128;
int cb = pcb[i] - 128;
r = y_fixed + cr * stbi__float2fixed(1.40200f);
g = y_fixed + (cr * -stbi__float2fixed(0.71414f)) +
((cb * -stbi__float2fixed(0.34414f)) & 0xffff0000);
b = y_fixed + cb * stbi__float2fixed(1.77200f);
r >>= 20;
g >>= 20;
b >>= 20;
if ((unsigned)r > 255) {
if (r < 0)
r = 0;
else
r = 255;
}
if ((unsigned)g > 255) {
if (g < 0)
g = 0;
else
g = 255;
}
if ((unsigned)b > 255) {
if (b < 0)
b = 0;
else
b = 255;
}
out[0] = (unsigned char)r;
out[1] = (unsigned char)g;
out[2] = (unsigned char)b;
out[3] = 255;
out += step;
}
}
#if defined(STBI_SSE2) || defined(STBI_NEON)
static void stbi__YCbCr_to_RGB_simd(unsigned char *out, unsigned char const *y,
unsigned char const *pcb,
unsigned char const *pcr, int count,
int step) {
int i = 0;
#ifdef STBI_SSE2
// step == 3 is pretty ugly on the final interleave, and i'm not convinced
// it's useful in practice (you wouldn't use it for textures, for example).
// so just accelerate step == 4 case.
if (step == 4) {
// this is a fairly straightforward implementation and not super-optimized.
__m128i signflip = _mm_set1_epi8(-0x80);
__m128i cr_const0 = _mm_set1_epi16((short)(1.40200f * 4096.0f + 0.5f));
__m128i cr_const1 = _mm_set1_epi16(-(short)(0.71414f * 4096.0f + 0.5f));
__m128i cb_const0 = _mm_set1_epi16(-(short)(0.34414f * 4096.0f + 0.5f));
__m128i cb_const1 = _mm_set1_epi16((short)(1.77200f * 4096.0f + 0.5f));
__m128i y_bias = _mm_set1_epi8((char)(unsigned char)128);
__m128i xw = _mm_set1_epi16(255); // alpha channel
for (; i + 7 < count; i += 8) {
// load
__m128i y_bytes = _mm_loadl_epi64((__m128i *)(y + i));
__m128i cr_bytes = _mm_loadl_epi64((__m128i *)(pcr + i));
__m128i cb_bytes = _mm_loadl_epi64((__m128i *)(pcb + i));
__m128i cr_biased = _mm_xor_si128(cr_bytes, signflip); // -128
__m128i cb_biased = _mm_xor_si128(cb_bytes, signflip); // -128
// unpack to short (and left-shift cr, cb by 8)
__m128i yw = _mm_unpacklo_epi8(y_bias, y_bytes);
__m128i crw = _mm_unpacklo_epi8(_mm_setzero_si128(), cr_biased);
__m128i cbw = _mm_unpacklo_epi8(_mm_setzero_si128(), cb_biased);
// color transform
__m128i yws = _mm_srli_epi16(yw, 4);
__m128i cr0 = _mm_mulhi_epi16(cr_const0, crw);
__m128i cb0 = _mm_mulhi_epi16(cb_const0, cbw);
__m128i cb1 = _mm_mulhi_epi16(cbw, cb_const1);
__m128i cr1 = _mm_mulhi_epi16(crw, cr_const1);
__m128i rws = _mm_add_epi16(cr0, yws);
__m128i gwt = _mm_add_epi16(cb0, yws);
__m128i bws = _mm_add_epi16(yws, cb1);
__m128i gws = _mm_add_epi16(gwt, cr1);
// descale
__m128i rw = _mm_srai_epi16(rws, 4);
__m128i bw = _mm_srai_epi16(bws, 4);
__m128i gw = _mm_srai_epi16(gws, 4);
// back to byte, set up for transpose
__m128i brb = _mm_packus_epi16(rw, bw);
__m128i gxb = _mm_packus_epi16(gw, xw);
// transpose to interleave channels
__m128i t0 = _mm_unpacklo_epi8(brb, gxb);
__m128i t1 = _mm_unpackhi_epi8(brb, gxb);
__m128i o0 = _mm_unpacklo_epi16(t0, t1);
__m128i o1 = _mm_unpackhi_epi16(t0, t1);
// store
_mm_storeu_si128((__m128i *)(out + 0), o0);
_mm_storeu_si128((__m128i *)(out + 16), o1);
out += 32;
}
}
#endif
#ifdef STBI_NEON
// in this version, step=3 support would be easy to add. but is there demand?
if (step == 4) {
// this is a fairly straightforward implementation and not super-optimized.
uint8x8_t signflip = vdup_n_u8(0x80);
int16x8_t cr_const0 = vdupq_n_s16((short)(1.40200f * 4096.0f + 0.5f));
int16x8_t cr_const1 = vdupq_n_s16(-(short)(0.71414f * 4096.0f + 0.5f));
int16x8_t cb_const0 = vdupq_n_s16(-(short)(0.34414f * 4096.0f + 0.5f));
int16x8_t cb_const1 = vdupq_n_s16((short)(1.77200f * 4096.0f + 0.5f));
for (; i + 7 < count; i += 8) {
// load
uint8x8_t y_bytes = vld1_u8(y + i);
uint8x8_t cr_bytes = vld1_u8(pcr + i);
uint8x8_t cb_bytes = vld1_u8(pcb + i);
int8x8_t cr_biased = vreinterpret_s8_u8(vsub_u8(cr_bytes, signflip));
int8x8_t cb_biased = vreinterpret_s8_u8(vsub_u8(cb_bytes, signflip));
// expand to s16
int16x8_t yws = vreinterpretq_s16_u16(vshll_n_u8(y_bytes, 4));
int16x8_t crw = vshll_n_s8(cr_biased, 7);
int16x8_t cbw = vshll_n_s8(cb_biased, 7);
// color transform
int16x8_t cr0 = vqdmulhq_s16(crw, cr_const0);
int16x8_t cb0 = vqdmulhq_s16(cbw, cb_const0);
int16x8_t cr1 = vqdmulhq_s16(crw, cr_const1);
int16x8_t cb1 = vqdmulhq_s16(cbw, cb_const1);
int16x8_t rws = vaddq_s16(yws, cr0);
int16x8_t gws = vaddq_s16(vaddq_s16(yws, cb0), cr1);
int16x8_t bws = vaddq_s16(yws, cb1);
// undo scaling, round, convert to byte
uint8x8x4_t o;
o.val[0] = vqrshrun_n_s16(rws, 4);
o.val[1] = vqrshrun_n_s16(gws, 4);
o.val[2] = vqrshrun_n_s16(bws, 4);
o.val[3] = vdup_n_u8(255);
// store, interleaving r/g/b/a
vst4_u8(out, o);
out += 8 * 4;
}
}
#endif
for (; i < count; ++i) {
int y_fixed = (y[i] << 20) + (1 << 19); // rounding
int r, g, b;
int cr = pcr[i] - 128;
int cb = pcb[i] - 128;
r = y_fixed + cr * stbi__float2fixed(1.40200f);
g = y_fixed + cr * -stbi__float2fixed(0.71414f) +
((cb * -stbi__float2fixed(0.34414f)) & 0xffff0000);
b = y_fixed + cb * stbi__float2fixed(1.77200f);
r >>= 20;
g >>= 20;
b >>= 20;
if ((unsigned)r > 255) {
if (r < 0)
r = 0;
else
r = 255;
}
if ((unsigned)g > 255) {
if (g < 0)
g = 0;
else
g = 255;
}
if ((unsigned)b > 255) {
if (b < 0)
b = 0;
else
b = 255;
}
out[0] = (unsigned char)r;
out[1] = (unsigned char)g;
out[2] = (unsigned char)b;
out[3] = 255;
out += step;
}
}
#endif
// set up the kernels
static void stbi__setup_jpeg(stbi__jpeg *j) {
j->resample_row_hv_2_kernel = stbi__resample_row_hv_2;
#if 0
if (stbi__sse2_available()) {
j->resample_row_hv_2_kernel = stbi__resample_row_hv_2_simd;
}
#endif
}
// clean up the temporary component buffers
static void stbi__cleanup_jpeg(stbi__jpeg *j) {
stbi__free_jpeg_components(j, j->s->img_n, 0);
}
typedef struct {
resample_row_func resample;
unsigned char *line0, *line1;
int hs, vs; // expansion factor in each axis
int w_lores; // horizontal pixels pre-expansion
int ystep; // how far through vertical expansion we are
int ypos; // which pre-expansion row we're on
} stbi__resample;
// fast 0..255 * 0..255 => 0..255 rounded multiplication
static unsigned char stbi__blinn_8x8(unsigned char x, unsigned char y) {
unsigned t;
t = x * y + 128;
return (t + (t >> 8)) >> 8;
}
static unsigned char *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y,
int *comp, int req_comp) {
int n, decode_n, is_rgb;
z->s->img_n = 0; // make stbi__cleanup_jpeg safe
// validate req_comp
if (req_comp < 0 || req_comp > 4) {
return stbi__errpuc("bad req_comp", "Internal error");
}
// load a jpeg image from whichever source, but leave in YCbCr format
if (!stbi__decode_jpeg_image(z)) {
stbi__cleanup_jpeg(z);
return NULL;
}
// determine actual number of components to generate
n = req_comp ? req_comp : z->s->img_n >= 3 ? 3 : 1;
is_rgb = z->s->img_n == 3 &&
(z->rgb == 3 || (z->app14_color_transform == 0 && !z->jfif));
if (z->s->img_n == 3 && n < 3 && !is_rgb) {
decode_n = 1;
} else {
decode_n = z->s->img_n;
}
// nothing to do if no components requested; check this now to avoid
// accessing uninitialized coutput[0] later
if (decode_n <= 0) {
stbi__cleanup_jpeg(z);
return NULL;
}
// resample and color-convert
{
int k;
unsigned int i, j;
unsigned char *output;
unsigned char *coutput[4];
stbi__resample res_comp[4];
bzero(coutput, sizeof(coutput));
for (k = 0; k < decode_n; ++k) {
stbi__resample *r = &res_comp[k];
// allocate line buffer big enough for upsampling off the edges
// with upsample factor of 4
z->img_comp[k].linebuf = xmalloc(z->s->img_x + 3);
r->hs = z->img_h_max / z->img_comp[k].h;
r->vs = z->img_v_max / z->img_comp[k].v;
r->ystep = r->vs >> 1;
r->w_lores = (z->s->img_x + r->hs - 1) / r->hs;
r->ypos = 0;
r->line0 = r->line1 = z->img_comp[k].data;
if (r->hs == 1 && r->vs == 1) {
r->resample = resample_row_1;
} else if (r->hs == 1 && r->vs == 2) {
r->resample = stbi__resample_row_v_2;
} else if (r->hs == 2 && r->vs == 1) {
r->resample = stbi__resample_row_h_2;
} else if (r->hs == 2 && r->vs == 2) {
r->resample = z->resample_row_hv_2_kernel;
} else {
r->resample = stbi__resample_row_nearest;
}
}
// can't error after this so, this is safe
output = stbi__malloc_mad3(n, z->s->img_x, z->s->img_y, 1);
// now go ahead and resample
for (j = 0; j < z->s->img_y; ++j) {
unsigned char *out = output + n * z->s->img_x * j;
for (k = 0; k < decode_n; ++k) {
stbi__resample *r = &res_comp[k];
int y_bot = r->ystep >= (r->vs >> 1);
coutput[k] =
r->resample(z->img_comp[k].linebuf, y_bot ? r->line1 : r->line0,
y_bot ? r->line0 : r->line1, r->w_lores, r->hs);
if (++r->ystep >= r->vs) {
r->ystep = 0;
r->line0 = r->line1;
if (++r->ypos < z->img_comp[k].y) r->line1 += z->img_comp[k].w2;
}
}
if (n >= 3) {
unsigned char *y = coutput[0];
if (z->s->img_n == 3) {
if (is_rgb) {
for (i = 0; i < z->s->img_x; ++i) {
out[0] = y[i];
out[1] = coutput[1][i];
out[2] = coutput[2][i];
out[3] = 255;
out += n;
}
} else {
stbi__YCbCr_to_RGB_row(out, y, coutput[1], coutput[2], z->s->img_x,
n);
}
} else if (z->s->img_n == 4) {
if (z->app14_color_transform == 0) { // CMYK
for (i = 0; i < z->s->img_x; ++i) {
unsigned char m = coutput[3][i];
out[0] = stbi__blinn_8x8(coutput[0][i], m);
out[1] = stbi__blinn_8x8(coutput[1][i], m);
out[2] = stbi__blinn_8x8(coutput[2][i], m);
out[3] = 255;
out += n;
}
} else if (z->app14_color_transform == 2) { // YCCK
stbi__YCbCr_to_RGB_row(out, y, coutput[1], coutput[2], z->s->img_x,
n);
for (i = 0; i < z->s->img_x; ++i) {
unsigned char m = coutput[3][i];
out[0] = stbi__blinn_8x8(255 - out[0], m);
out[1] = stbi__blinn_8x8(255 - out[1], m);
out[2] = stbi__blinn_8x8(255 - out[2], m);
out += n;
}
} else { // YCbCr + alpha? Ignore the fourth channel for now
stbi__YCbCr_to_RGB_row(out, y, coutput[1], coutput[2], z->s->img_x,
n);
}
} else
for (i = 0; i < z->s->img_x; ++i) {
out[0] = out[1] = out[2] = y[i];
out[3] = 255; // not used if n==3
out += n;
}
} else {
if (is_rgb) {
if (n == 1)
for (i = 0; i < z->s->img_x; ++i)
*out++ =
stbi__compute_y(coutput[0][i], coutput[1][i], coutput[2][i]);
else {
for (i = 0; i < z->s->img_x; ++i, out += 2) {
out[0] =
stbi__compute_y(coutput[0][i], coutput[1][i], coutput[2][i]);
out[1] = 255;
}
}
} else if (z->s->img_n == 4 && z->app14_color_transform == 0) {
for (i = 0; i < z->s->img_x; ++i) {
unsigned char m = coutput[3][i];
unsigned char r = stbi__blinn_8x8(coutput[0][i], m);
unsigned char g = stbi__blinn_8x8(coutput[1][i], m);
unsigned char b = stbi__blinn_8x8(coutput[2][i], m);
out[0] = stbi__compute_y(r, g, b);
out[1] = 255;
out += n;
}
} else if (z->s->img_n == 4 && z->app14_color_transform == 2) {
for (i = 0; i < z->s->img_x; ++i) {
out[0] = stbi__blinn_8x8(255 - coutput[0][i], coutput[3][i]);
out[1] = 255;
out += n;
}
} else {
unsigned char *y = coutput[0];
if (n == 1)
for (i = 0; i < z->s->img_x; ++i) out[i] = y[i];
else
for (i = 0; i < z->s->img_x; ++i) {
*out++ = y[i];
*out++ = 255;
}
}
}
}
stbi__cleanup_jpeg(z);
*out_x = z->s->img_x;
*out_y = z->s->img_y;
if (comp)
*comp =
z->s->img_n >= 3 ? 3 : 1; // report original components, not output
return output;
}
}
static dontinline void *stbi__jpeg_load(stbi__context *s, int *x, int *y,
int *comp, int req_comp,
stbi__result_info *ri) {
unsigned char *result;
stbi__jpeg *j;
j = malloc(sizeof(stbi__jpeg));
if (!j) return stbi__errpuc("outofmem", "Out of memory");
bzero(j, sizeof(stbi__jpeg));
j->s = s;
stbi__setup_jpeg(j);
result = load_jpeg_image(j, x, y, comp, req_comp);
free(j);
return result;
}
static int stbi__jpeg_test(stbi__context *s) {
int r;
stbi__jpeg *j;
j = malloc(sizeof(stbi__jpeg));
if (!j) return stbi__err("outofmem", "Out of memory");
bzero(j, sizeof(stbi__jpeg));
j->s = s;
stbi__setup_jpeg(j);
r = stbi__decode_jpeg_header(j, STBI__SCAN_type);
stbi__rewind(s);
free(j);
return r;
}
static int stbi__jpeg_info_raw(stbi__jpeg *j, int *x, int *y, int *comp) {
if (!stbi__decode_jpeg_header(j, STBI__SCAN_header)) {
stbi__rewind(j->s);
return 0;
}
if (x) *x = j->s->img_x;
if (y) *y = j->s->img_y;
if (comp) *comp = j->s->img_n >= 3 ? 3 : 1;
return 1;
}
static int stbi__jpeg_info(stbi__context *s, int *x, int *y, int *comp) {
int result;
stbi__jpeg *j = (stbi__jpeg *)(malloc(sizeof(stbi__jpeg)));
if (!j) return stbi__err("outofmem", "Out of memory");
bzero(j, sizeof(stbi__jpeg));
j->s = s;
result = stbi__jpeg_info_raw(j, x, y, comp);
free(j);
return result;
}
// public domain zlib decode v0.2 Sean Barrett 2006-11-18
// simple implementation
// - all input must be provided in an upfront buffer
// - all output is written to a single output buffer (can malloc/realloc)
// performance
// - fast huffman
// fast-way is faster to check than jpeg huffman, but slow way is slower
#define STBI__ZFAST_BITS 9 // accelerate all cases in default tables
#define STBI__ZFAST_MASK ((1 << STBI__ZFAST_BITS) - 1)
#define STBI__ZNSYMS 288 // number of symbols in literal/length alphabet
// zlib-style huffman encoding
// (jpegs packs from left, zlib from right, so can't share code)
typedef struct {
uint16_t fast[1 << STBI__ZFAST_BITS];
uint16_t firstcode[16];
int maxcode[17];
uint16_t firstsymbol[16];
unsigned char size[STBI__ZNSYMS];
uint16_t value[STBI__ZNSYMS];
} stbi__zhuffman;
static uint32_t ReverseBits32(uint32_t x) {
x = bswap_32(x);
x = (x & 0xaaaaaaaa) >> 1 | (x & 0x55555555) << 1;
x = (x & 0xcccccccc) >> 2 | (x & 0x33333333) << 2;
x = (x & 0xf0f0f0f0) >> 4 | (x & 0x0f0f0f0f) << 4;
return x;
}
static int ReverseBits16(int x) {
return ReverseBits32(x) >> 16;
}
forceinline int stbi__bit_reverse(int v, int bits) {
assert(bits <= 16);
// to bit reverse n bits, reverse 16 and shift
// e.g. 11 bits, bit reverse and shift away 5
return ReverseBits16(v) >> (16 - bits);
}
static int stbi__zbuild_huffman(stbi__zhuffman *z,
const unsigned char *sizelist, int num) {
int i, k = 0;
int code, next_code[16], sizes[17];
// DEFLATE spec for generating codes
bzero(sizes, sizeof(sizes));
bzero(z->fast, sizeof(z->fast));
for (i = 0; i < num; ++i) ++sizes[sizelist[i]];
sizes[0] = 0;
for (i = 1; i < 16; ++i)
if (sizes[i] > (1 << i)) return stbi__err("bad sizes", "Corrupt PNG");
code = 0;
for (i = 1; i < 16; ++i) {
next_code[i] = code;
z->firstcode[i] = (uint16_t)code;
z->firstsymbol[i] = (uint16_t)k;
code = (code + sizes[i]);
if (sizes[i])
if (code - 1 >= (1 << i))
return stbi__err("bad codelengths", "Corrupt PNG");
z->maxcode[i] = code << (16 - i); // preshift for inner loop
code <<= 1;
k += sizes[i];
}
z->maxcode[16] = 0x10000; // sentinel
for (i = 0; i < num; ++i) {
int s = sizelist[i];
if (s) {
int c = next_code[s] - z->firstcode[s] + z->firstsymbol[s];
uint16_t fastv = (uint16_t)((s << 9) | i);
z->size[c] = (unsigned char)s;
z->value[c] = (uint16_t)i;
if (s <= STBI__ZFAST_BITS) {
int j = stbi__bit_reverse(next_code[s], s);
while (j < (1 << STBI__ZFAST_BITS)) {
z->fast[j] = fastv;
j += (1 << s);
}
}
++next_code[s];
}
}
return 1;
}
// zlib-from-memory implementation for PNG reading
// because PNG allows splitting the zlib stream arbitrarily,
// and it's annoying structurally to have PNG call ZLIB call PNG,
// we require PNG read all the IDATs and combine them into a single
// memory buffer
typedef struct {
unsigned char *zbuffer, *zbuffer_end;
int num_bits;
int hit_zeof_once;
uint32_t code_buffer;
char *zout;
char *zout_start;
char *zout_end;
int z_expandable;
stbi__zhuffman z_length, z_distance;
} stbi__zbuf;
forceinline int stbi__zeof(stbi__zbuf *z) {
return (z->zbuffer >= z->zbuffer_end);
}
forceinline unsigned char stbi__zget8(stbi__zbuf *z) {
return stbi__zeof(z) ? 0 : *z->zbuffer++;
}
static void stbi__fill_bits(stbi__zbuf *z) {
do {
if (z->code_buffer >= (1u << z->num_bits)) {
z->zbuffer = z->zbuffer_end; // treat this as EOF so we fail.
return;
}
z->code_buffer |= (unsigned int)stbi__zget8(z) << z->num_bits;
z->num_bits += 8;
} while (z->num_bits <= 24);
}
forceinline unsigned int stbi__zreceive(stbi__zbuf *z, int n) {
unsigned int k;
if (z->num_bits < n) stbi__fill_bits(z);
k = z->code_buffer & ((1 << n) - 1);
z->code_buffer >>= n;
z->num_bits -= n;
return k;
}
static int stbi__zhuffman_decode_slowpath(stbi__zbuf *a, stbi__zhuffman *z) {
int b, s, k;
// not resolved by fast table, so compute it the slow way
// use jpeg approach, which requires MSbits at top
k = stbi__bit_reverse(a->code_buffer, 16);
for (s = STBI__ZFAST_BITS + 1;; ++s)
if (k < z->maxcode[s]) break;
if (s >= 16) return -1; // invalid code!
// code size is s, so:
b = (k >> (16 - s)) - z->firstcode[s] + z->firstsymbol[s];
if (b >= STBI__ZNSYMS) {
// some data was corrupt somewhere!
return -1;
}
if (z->size[b] != s) {
// was originally an assert, but report failure instead.
return -1;
}
a->code_buffer >>= s;
a->num_bits -= s;
return z->value[b];
}
forceinline int stbi__zhuffman_decode(stbi__zbuf *a, stbi__zhuffman *z) {
int b, s;
if (a->num_bits < 16) {
if (stbi__zeof(a)) {
if (!a->hit_zeof_once) {
// This is the first time we hit eof, insert 16 extra padding bits
// to allow us to keep going; if we actually consume any of them
// though, that is invalid data. This is caught later.
a->hit_zeof_once = 1;
a->num_bits += 16; // add 16 implicit zero bits
} else {
// We already inserted our extra 16 padding bits and are again
// out, this stream is actually prematurely terminated.
return -1;
}
} else {
stbi__fill_bits(a);
}
}
b = z->fast[a->code_buffer & STBI__ZFAST_MASK];
if (b) {
s = b >> 9;
a->code_buffer >>= s;
a->num_bits -= s;
return b & 511;
}
return stbi__zhuffman_decode_slowpath(a, z);
}
static int stbi__zexpand(stbi__zbuf *z, char *zout, int n) {
char *q;
unsigned int cur, limit;
z->zout = zout;
if (!z->z_expandable) return stbi__err("output buffer limit", "Corrupt PNG");
cur = (unsigned int)(z->zout - z->zout_start);
limit = (unsigned)(z->zout_end - z->zout_start);
if (UINT_MAX - cur < (unsigned)n) {
return stbi__err("outofmem", "Out of memory");
}
while (cur + n > limit) {
if (limit > UINT_MAX / 2) return stbi__err("outofmem", "Out of memory");
limit *= 2;
}
q = (char *)realloc(z->zout_start, limit);
if (q == NULL) return stbi__err("outofmem", "Out of memory");
z->zout_start = q;
z->zout = q + cur;
z->zout_end = q + limit;
return 1;
}
static const int stbi__zlength_base[31] = {
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0,
};
static const int stbi__zlength_extra[31] = {
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 0, 0,
};
static const int stbi__zdist_base[32] = {
1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33,
49, 65, 97, 129, 193, 257, 385, 513, 769, 1025, 1537,
2049, 3073, 4097, 6145, 8193, 12289, 16385, 24577, 0, 0,
};
static const int stbi__zdist_extra[32] = {
0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6,
6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13,
};
static int stbi__parse_huffman_block(stbi__zbuf *a) {
char *zout = a->zout;
for (;;) {
int z = stbi__zhuffman_decode(a, &a->z_length);
if (z < 256) {
if (z < 0) return stbi__err("bad huffman code", "Corrupt PNG");
if (zout >= a->zout_end) {
if (!stbi__zexpand(a, zout, 1)) return 0;
zout = a->zout;
}
*zout++ = (char)z;
} else {
unsigned char *p;
int len, dist;
if (z == 256) {
a->zout = zout;
if (a->hit_zeof_once && a->num_bits < 16) {
// The first time we hit zeof, we inserted 16 extra zero bits into our
// bit buffer so the decoder can just do its speculative decoding. But
// if we actually consumed any of those bits (which is the case when
// num_bits < 16), the stream actually read past the end so it is
// malformed.
return stbi__err("unexpected end", "Corrupt PNG");
}
return 1;
}
if (z >= 286) {
// per DEFLATE, length codes 286 and 287
// must not appear in compressed data
return stbi__err("bad huffman code", "Corrupt PNG");
}
z -= 257;
len = stbi__zlength_base[z];
if (stbi__zlength_extra[z])
len += stbi__zreceive(a, stbi__zlength_extra[z]);
z = stbi__zhuffman_decode(a, &a->z_distance);
if (z < 0 || z >= 30) {
// per DEFLATE, distance codes 30 and 31
// must not appear in compressed data
return stbi__err("bad huffman code", "Corrupt PNG");
}
dist = stbi__zdist_base[z];
if (stbi__zdist_extra[z]) dist += stbi__zreceive(a, stbi__zdist_extra[z]);
if (zout - a->zout_start < dist)
return stbi__err("bad dist", "Corrupt PNG");
if (len > a->zout_end - zout) {
if (!stbi__zexpand(a, zout, len)) return 0;
zout = a->zout;
}
p = (unsigned char *)(zout - dist);
if (dist == 1) { // run of one byte; common in images.
unsigned char v = *p;
if (len) {
do *zout++ = v;
while (--len);
}
} else {
if (len) {
do *zout++ = *p++;
while (--len);
}
}
}
}
}
static int stbi__compute_huffman_codes(stbi__zbuf *a) {
static const unsigned char length_dezigzag[19] = {
16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
stbi__zhuffman z_codelength;
unsigned char lencodes[286 + 32 + 137]; // padding for maximum single op
unsigned char codelength_sizes[19];
int i, n;
int hlit = stbi__zreceive(a, 5) + 257;
int hdist = stbi__zreceive(a, 5) + 1;
int hclen = stbi__zreceive(a, 4) + 4;
int ntot = hlit + hdist;
bzero(codelength_sizes, sizeof(codelength_sizes));
for (i = 0; i < hclen; ++i) {
int s = stbi__zreceive(a, 3);
codelength_sizes[length_dezigzag[i]] = (unsigned char)s;
}
if (!stbi__zbuild_huffman(&z_codelength, codelength_sizes, 19)) return 0;
n = 0;
while (n < ntot) {
int c = stbi__zhuffman_decode(a, &z_codelength);
if (c < 0 || c >= 19) return stbi__err("bad codelengths", "Corrupt PNG");
if (c < 16)
lencodes[n++] = (unsigned char)c;
else {
unsigned char fill = 0;
if (c == 16) {
c = stbi__zreceive(a, 2) + 3;
if (n == 0) return stbi__err("bad codelengths", "Corrupt PNG");
fill = lencodes[n - 1];
} else if (c == 17) {
c = stbi__zreceive(a, 3) + 3;
} else if (c == 18) {
c = stbi__zreceive(a, 7) + 11;
} else {
return stbi__err("bad codelengths", "Corrupt PNG");
}
if (ntot - n < c) return stbi__err("bad codelengths", "Corrupt PNG");
memset(lencodes + n, fill, c);
n += c;
}
}
if (n != ntot) return stbi__err("bad codelengths", "Corrupt PNG");
if (!stbi__zbuild_huffman(&a->z_length, lencodes, hlit)) return 0;
if (!stbi__zbuild_huffman(&a->z_distance, lencodes + hlit, hdist)) return 0;
return 1;
}
static int stbi__parse_uncompressed_block(stbi__zbuf *a) {
unsigned char header[4];
int len, nlen, k;
if (a->num_bits & 7) stbi__zreceive(a, a->num_bits & 7); // discard
// drain the bit-packed data into header
k = 0;
while (a->num_bits > 0) {
header[k++] =
(unsigned char)(a->code_buffer & 255); // suppress MSVC run-time check
a->code_buffer >>= 8;
a->num_bits -= 8;
}
if (a->num_bits < 0) return stbi__err("zlib corrupt", "Corrupt PNG");
// now fill header the normal way
while (k < 4) header[k++] = stbi__zget8(a);
len = header[1] * 256 + header[0];
nlen = header[3] * 256 + header[2];
if (nlen != (len ^ 0xffff)) return stbi__err("zlib corrupt", "Corrupt PNG");
if (a->zbuffer + len > a->zbuffer_end)
return stbi__err("read past buffer", "Corrupt PNG");
if (a->zout + len > a->zout_end)
if (!stbi__zexpand(a, a->zout, len)) return 0;
memcpy(a->zout, a->zbuffer, len);
a->zbuffer += len;
a->zout += len;
return 1;
}
static int stbi__parse_zlib_header(stbi__zbuf *a) {
int cmf = stbi__zget8(a);
int cm = cmf & 15;
/* int cinfo = cmf >> 4; */
int flg = stbi__zget8(a);
if (stbi__zeof(a))
return stbi__err("bad zlib header", "Corrupt PNG"); // zlib spec
if ((cmf * 256 + flg) % 31 != 0)
return stbi__err("bad zlib header", "Corrupt PNG"); // zlib spec
if (flg & 32)
return stbi__err("no preset dict",
"Corrupt PNG"); // preset dictionary not allowed in png
if (cm != 8)
return stbi__err("bad compression",
"Corrupt PNG"); // DEFLATE required for png
// window = 1 << (8 + cinfo)... but who cares, we fully buffer output
return 1;
}
static const unsigned char stbi__zdefault_length[STBI__ZNSYMS] = {
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8};
static const unsigned char stbi__zdefault_distance[32] = {
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
};
/*
Init algorithm:{
int i; // use <= to match clearly with spec
for (i=0; i <= 143; ++i) stbi__zdefault_length[i] = 8;
for ( ; i <= 255; ++i) stbi__zdefault_length[i] = 9;
for ( ; i <= 279; ++i) stbi__zdefault_length[i] = 7;
for ( ; i <= 287; ++i) stbi__zdefault_length[i] = 8;
for (i=0; i <= 31; ++i) stbi__zdefault_distance[i] = 5;
}
*/
static int stbi__parse_zlib(stbi__zbuf *a, int parse_header) {
int final, type;
if (parse_header)
if (!stbi__parse_zlib_header(a)) return 0;
a->num_bits = 0;
a->code_buffer = 0;
a->hit_zeof_once = 0;
do {
final = stbi__zreceive(a, 1);
type = stbi__zreceive(a, 2);
if (type == 0) {
if (!stbi__parse_uncompressed_block(a)) return 0;
} else if (type == 3) {
return 0;
} else {
if (type == 1) {
// use fixed code lengths
if (!stbi__zbuild_huffman(&a->z_length, stbi__zdefault_length,
STBI__ZNSYMS))
return 0;
if (!stbi__zbuild_huffman(&a->z_distance, stbi__zdefault_distance, 32))
return 0;
} else {
if (!stbi__compute_huffman_codes(a)) return 0;
}
if (!stbi__parse_huffman_block(a)) return 0;
}
} while (!final);
return 1;
}
static int stbi__do_zlib(stbi__zbuf *a, char *obuf, int olen, int exp,
int parse_header) {
a->zout_start = obuf;
a->zout = obuf;
a->zout_end = obuf + olen;
a->z_expandable = exp;
return stbi__parse_zlib(a, parse_header);
}
char *stbi_zlib_decode_malloc_guesssize(const char *buffer, int len,
int initial_size, int *outlen) {
char *res, *p;
stbi__zbuf *a;
a = NULL;
res = NULL;
if ((p = (char *)malloc(initial_size)) &&
(a = (stbi__zbuf *)malloc(sizeof(stbi__zbuf)))) {
a->zbuffer = (unsigned char *)buffer;
a->zbuffer_end = (unsigned char *)buffer + len;
if (stbi__do_zlib(a, p, initial_size, 1, 1)) {
if (outlen) *outlen = (int)(a->zout - a->zout_start);
res = a->zout_start;
a->zout_start = NULL;
}
}
free(a->zout_start);
free(a);
return res;
}
char *stbi_zlib_decode_malloc(char const *buffer, int len, int *outlen) {
return stbi_zlib_decode_malloc_guesssize(buffer, len, 16384, outlen);
}
char *stbi_zlib_decode_malloc_guesssize_headerflag(const char *buffer, int len,
int initial_size,
int *outlen,
int parse_header) {
char *res;
stbi__zbuf *a = malloc(sizeof(stbi__zbuf));
char *p = (char *)malloc(initial_size);
if (!p) return NULL;
a->zbuffer = (unsigned char *)buffer;
a->zbuffer_end = (unsigned char *)buffer + len;
if (stbi__do_zlib(a, p, initial_size, 1, parse_header)) {
if (outlen) *outlen = (int)(a->zout - a->zout_start);
res = a->zout_start;
} else {
free(a->zout_start);
res = NULL;
}
free(a);
return res;
}
int stbi_zlib_decode_buffer(char *obuffer, int olen, char const *ibuffer,
int ilen) {
stbi__zbuf a;
a.zbuffer = (unsigned char *)ibuffer;
a.zbuffer_end = (unsigned char *)ibuffer + ilen;
if (stbi__do_zlib(&a, obuffer, olen, 0, 1))
return (int)(a.zout - a.zout_start);
else
return -1;
}
char *stbi_zlib_decode_noheader_malloc(char const *buffer, int len,
int *outlen) {
stbi__zbuf a;
char *p = (char *)malloc(16384);
if (p == NULL) return NULL;
a.zbuffer = (unsigned char *)buffer;
a.zbuffer_end = (unsigned char *)buffer + len;
if (stbi__do_zlib(&a, p, 16384, 1, 0)) {
if (outlen) *outlen = (int)(a.zout - a.zout_start);
return a.zout_start;
} else {
free(a.zout_start);
return NULL;
}
}
int stbi_zlib_decode_noheader_buffer(char *obuffer, int olen,
const char *ibuffer, int ilen) {
stbi__zbuf a;
a.zbuffer = (unsigned char *)ibuffer;
a.zbuffer_end = (unsigned char *)ibuffer + ilen;
if (stbi__do_zlib(&a, obuffer, olen, 0, 0))
return (int)(a.zout - a.zout_start);
else
return -1;
}
// public domain "baseline" PNG decoder v0.10 Sean Barrett 2006-11-18
// simple implementation
// - only 8-bit samples
// - no CRC checking
// - allocates lots of intermediate memory
// - avoids problem of streaming data between subsystems
// - avoids explicit window management
// performance
// - uses stb_zlib, a PD zlib implementation with fast huffman decoding
typedef struct {
uint32_t length;
uint32_t type;
} stbi__pngchunk;
static stbi__pngchunk stbi__get_chunk_header(stbi__context *s) {
stbi__pngchunk c;
c.length = stbi__get32be(s);
c.type = stbi__get32be(s);
return c;
}
static int stbi__check_png_header(stbi__context *s) {
int i;
for (i = 0; i < 8; ++i) {
if (stbi__get8(s) != kPngSig[i]) {
return stbi__err("bad png sig", "Not a PNG");
}
}
return 1;
}
typedef struct {
stbi__context *s;
unsigned char *idata, *expanded, *out;
int depth;
} stbi__png;
enum {
STBI__F_none = 0,
STBI__F_sub = 1,
STBI__F_up = 2,
STBI__F_avg = 3,
STBI__F_paeth = 4,
// synthetic filter used for first scanline to avoid needing a dummy row of 0s
STBI__F_avg_first
};
static int stbi__de_iphone_flag = 0;
static int stbi__unpremultiply_on_load = 0;
static unsigned char first_row_filter[5] = {
STBI__F_none, STBI__F_sub, STBI__F_none, STBI__F_avg_first,
STBI__F_sub // Paeth with b = c = 0 turns out to be equivalent to sub
};
static int stbi__paeth(int a, int b, int c) {
// This formulation looks very different from the reference in the PNG spec,
// but is actually equivalent and has favorable data dependencies and admits
// straightforward generation of branch-free code, which helps performance
// significantly.
int thresh = c * 3 - (a + b);
int lo = a < b ? a : b;
int hi = a < b ? b : a;
int t0 = (hi <= thresh) ? lo : c;
int t1 = (thresh <= lo) ? hi : t0;
return t1;
}
static const unsigned char stbi__depth_scale_table[9] = {
0, 0xff, 0x55, 0, 0x11, 0, 0, 0, 0x01};
// adds an extra all-255 alpha channel
// dest == src is legal
// img_n must be 1 or 3
static void stbi__create_png_alpha_expand8(unsigned char *dest,
unsigned char *src, uint32_t x,
int img_n) {
int i;
// must process data backwards since we allow dest==src
if (img_n == 1) {
for (i = x - 1; i >= 0; --i) {
dest[i * 2 + 1] = 255;
dest[i * 2 + 0] = src[i];
}
} else {
assert(img_n == 3);
for (i = x - 1; i >= 0; --i) {
dest[i * 4 + 3] = 255;
dest[i * 4 + 2] = src[i * 3 + 2];
dest[i * 4 + 1] = src[i * 3 + 1];
dest[i * 4 + 0] = src[i * 3 + 0];
}
}
}
// create the png data from post-deflated data
static int stbi__create_png_image_raw(stbi__png *a, unsigned char *raw,
uint32_t raw_len, int out_n, uint32_t x,
uint32_t y, int depth, int color) {
int bytes = (depth == 16 ? 2 : 1);
stbi__context *s = a->s;
uint32_t i, j, stride = x * out_n * bytes;
uint32_t img_len, img_width_bytes;
unsigned char *filler_buf;
int all_ok = 1;
int k;
int img_n = s->img_n; // copy it into a local for later
int output_bytes = out_n * bytes;
int filter_bytes = img_n * bytes;
int width = x;
assert(out_n == s->img_n || out_n == s->img_n + 1);
a->out = stbi__malloc_mad3(x, y, output_bytes,
0); // extra bytes to write off the end into
// note: error exits here don't need to clean up a->out individually,
// stbi__do_png always does on error.
if (!stbi__mad3sizes_valid(img_n, x, depth, 7))
return stbi__err("too large", "Corrupt PNG");
img_width_bytes = (((img_n * x * depth) + 7) >> 3);
if (!stbi__mad2sizes_valid(img_width_bytes, y, img_width_bytes))
return stbi__err("too large", "Corrupt PNG");
img_len = (img_width_bytes + 1) * y;
// we used to check for exact match between raw_len and img_len on
// non-interlaced PNGs, but issue #276 reported a PNG in the wild that had
// extra data at the end (all zeros), so just check for raw_len < img_len
// always.
if (raw_len < img_len) return stbi__err("not enough pixels", "Corrupt PNG");
// Allocate two scan lines worth of filter workspace buffer.
filler_buf = stbi__malloc_mad2(img_width_bytes, 2, 0);
if (!filler_buf) return stbi__err("outofmem", "Out of memory");
// Filtering for low-bit-depth images
if (depth < 8) {
filter_bytes = 1;
width = img_width_bytes;
}
for (j = 0; j < y; ++j) {
// cur/prior filter buffers alternate
unsigned char *cur = filler_buf + (j & 1) * img_width_bytes;
unsigned char *prior = filler_buf + (~j & 1) * img_width_bytes;
unsigned char *dest = a->out + stride * j;
int nk = width * filter_bytes;
int filter = *raw++;
// check filter type
if (filter > 4) {
all_ok = stbi__err("invalid filter", "Corrupt PNG");
break;
}
// if first row, use special filter that doesn't sample previous row
if (j == 0) filter = first_row_filter[filter];
// perform actual filtering
switch (filter) {
case STBI__F_none:
memcpy(cur, raw, nk);
break;
case STBI__F_sub:
memcpy(cur, raw, filter_bytes);
for (k = filter_bytes; k < nk; ++k)
cur[k] = STBI__BYTECAST(raw[k] + cur[k - filter_bytes]);
break;
case STBI__F_up:
for (k = 0; k < nk; ++k) cur[k] = STBI__BYTECAST(raw[k] + prior[k]);
break;
case STBI__F_avg:
for (k = 0; k < filter_bytes; ++k)
cur[k] = STBI__BYTECAST(raw[k] + (prior[k] >> 1));
for (k = filter_bytes; k < nk; ++k)
cur[k] = STBI__BYTECAST(raw[k] +
((prior[k] + cur[k - filter_bytes]) >> 1));
break;
case STBI__F_paeth:
for (k = 0; k < filter_bytes; ++k)
// prior[k] == stbi__paeth(0, prior[k], 0)
cur[k] = STBI__BYTECAST(raw[k] + prior[k]);
for (k = filter_bytes; k < nk; ++k)
cur[k] = STBI__BYTECAST(raw[k] +
stbi__paeth(cur[k - filter_bytes], prior[k],
prior[k - filter_bytes]));
break;
case STBI__F_avg_first:
memcpy(cur, raw, filter_bytes);
for (k = filter_bytes; k < nk; ++k)
cur[k] = STBI__BYTECAST(raw[k] + (cur[k - filter_bytes] >> 1));
break;
}
raw += nk;
// expand decoded bits in cur to dest, also adding an extra alpha channel
// if desired
if (depth < 8) {
unsigned char scale = (color == 0)
? stbi__depth_scale_table[depth]
: 1; // scale grayscale values to 0..255 range
unsigned char *in = cur;
unsigned char *out = dest;
unsigned char inb = 0;
uint32_t nsmp = x * img_n;
// expand bits to bytes first
if (depth == 4) {
for (i = 0; i < nsmp; ++i) {
if ((i & 1) == 0) inb = *in++;
*out++ = scale * (inb >> 4);
inb <<= 4;
}
} else if (depth == 2) {
for (i = 0; i < nsmp; ++i) {
if ((i & 3) == 0) inb = *in++;
*out++ = scale * (inb >> 6);
inb <<= 2;
}
} else {
assert(depth == 1);
for (i = 0; i < nsmp; ++i) {
if ((i & 7) == 0) inb = *in++;
*out++ = scale * (inb >> 7);
inb <<= 1;
}
}
// insert alpha=255 values if desired
if (img_n != out_n) stbi__create_png_alpha_expand8(dest, dest, x, img_n);
} else if (depth == 8) {
if (img_n == out_n)
memcpy(dest, cur, x * img_n);
else
stbi__create_png_alpha_expand8(dest, cur, x, img_n);
} else if (depth == 16) {
// convert the image data from big-endian to platform-native
// TODO TYPES
uint16_t *dest16 = (uint16_t *)dest;
uint32_t nsmp = x * img_n;
if (img_n == out_n) {
for (i = 0; i < nsmp; ++i, ++dest16, cur += 2)
*dest16 = (cur[0] << 8) | cur[1];
} else {
assert(img_n + 1 == out_n);
if (img_n == 1) {
for (i = 0; i < x; ++i, dest16 += 2, cur += 2) {
dest16[0] = (cur[0] << 8) | cur[1];
dest16[1] = 0xffff;
}
} else {
assert(img_n == 3);
for (i = 0; i < x; ++i, dest16 += 4, cur += 6) {
dest16[0] = (cur[0] << 8) | cur[1];
dest16[1] = (cur[2] << 8) | cur[3];
dest16[2] = (cur[4] << 8) | cur[5];
dest16[3] = 0xffff;
}
}
}
}
}
free(filler_buf);
if (!all_ok) return 0;
return 1;
}
static int stbi__create_png_image(stbi__png *a, unsigned char *image_data,
uint32_t image_data_len, int out_n, int depth,
int color, int interlaced) {
int bytes = (depth == 16 ? 2 : 1);
int out_bytes = out_n * bytes;
unsigned char *final;
int p;
if (!interlaced)
return stbi__create_png_image_raw(a, image_data, image_data_len, out_n,
a->s->img_x, a->s->img_y, depth, color);
// de-interlacing
final = stbi__malloc_mad3(a->s->img_x, a->s->img_y, out_bytes, 0);
if (!final) return stbi__err("outofmem", "Out of memory");
for (p = 0; p < 7; ++p) {
int xorig[] = {0, 4, 0, 2, 0, 1, 0};
int yorig[] = {0, 0, 4, 0, 2, 0, 1};
int xspc[] = {8, 8, 4, 4, 2, 2, 1};
int yspc[] = {8, 8, 8, 4, 4, 2, 2};
int i, j, x, y;
// pass1_x[4] = 0, pass1_x[5] = 1, pass1_x[12] = 1
x = (a->s->img_x - xorig[p] + xspc[p] - 1) / xspc[p];
y = (a->s->img_y - yorig[p] + yspc[p] - 1) / yspc[p];
if (x && y) {
uint32_t img_len = ((((a->s->img_n * x * depth) + 7) >> 3) + 1) * y;
if (!stbi__create_png_image_raw(a, image_data, image_data_len, out_n, x,
y, depth, color)) {
free(final);
return 0;
}
for (j = 0; j < y; ++j) {
for (i = 0; i < x; ++i) {
int out_y = j * yspc[p] + yorig[p];
int out_x = i * xspc[p] + xorig[p];
memcpy(final + out_y * a->s->img_x * out_bytes + out_x * out_bytes,
a->out + (j * x + i) * out_bytes, out_bytes);
}
}
free(a->out);
image_data += img_len;
image_data_len -= img_len;
}
}
a->out = final;
return 1;
}
static int stbi__compute_transparency(stbi__png *z, unsigned char tc[3],
int out_n) {
stbi__context *s = z->s;
uint32_t i, pixel_count = s->img_x * s->img_y;
unsigned char *p = z->out;
// compute color-based transparency, assuming we've
// already got 255 as the alpha value in the output
assert(out_n == 2 || out_n == 4);
if (out_n == 2) {
for (i = 0; i < pixel_count; ++i) {
p[1] = (p[0] == tc[0] ? 0 : 255);
p += 2;
}
} else {
for (i = 0; i < pixel_count; ++i) {
if (p[0] == tc[0] && p[1] == tc[1] && p[2] == tc[2]) p[3] = 0;
p += 4;
}
}
return 1;
}
static int stbi__compute_transparency16(stbi__png *z, uint16_t tc[3],
int out_n) {
stbi__context *s = z->s;
uint32_t i, pixel_count = s->img_x * s->img_y;
uint16_t *p = (uint16_t *)z->out;
// compute color-based transparency, assuming we've
// already got 65535 as the alpha value in the output
assert(out_n == 2 || out_n == 4);
if (out_n == 2) {
for (i = 0; i < pixel_count; ++i) {
p[1] = (p[0] == tc[0] ? 0 : 65535);
p += 2;
}
} else {
for (i = 0; i < pixel_count; ++i) {
if (p[0] == tc[0] && p[1] == tc[1] && p[2] == tc[2]) p[3] = 0;
p += 4;
}
}
return 1;
}
static int stbi__expand_png_palette(stbi__png *a, unsigned char *palette,
int len, int pal_img_n) {
uint32_t i, pixel_count = a->s->img_x * a->s->img_y;
unsigned char *p, *temp_out, *orig = a->out;
p = stbi__malloc_mad2(pixel_count, pal_img_n, 0);
// between here and free(out) below, exitting would leak
temp_out = p;
if (pal_img_n == 3) {
for (i = 0; i < pixel_count; ++i) {
int n = orig[i] * 4;
p[0] = palette[n];
p[1] = palette[n + 1];
p[2] = palette[n + 2];
p += 3;
}
} else {
for (i = 0; i < pixel_count; ++i) {
int n = orig[i] * 4;
p[0] = palette[n];
p[1] = palette[n + 1];
p[2] = palette[n + 2];
p[3] = palette[n + 3];
p += 4;
}
}
free(a->out);
a->out = temp_out;
return 1;
}
void stbi_set_unpremultiply_on_load(int flag_true_if_should_unpremultiply) {
stbi__unpremultiply_on_load = flag_true_if_should_unpremultiply;
}
void stbi_convert_iphone_png_to_rgb(int flag_true_if_should_convert) {
stbi__de_iphone_flag = flag_true_if_should_convert;
}
static void stbi__de_iphone(stbi__png *z) {
stbi__context *s = z->s;
uint32_t i, pixel_count = s->img_x * s->img_y;
unsigned char *p = z->out;
if (s->img_out_n == 3) { // convert bgr to rgb
for (i = 0; i < pixel_count; ++i) {
unsigned char t = p[0];
p[0] = p[2];
p[2] = t;
p += 3;
}
} else {
assert(s->img_out_n == 4);
if (stbi__unpremultiply_on_load) {
// convert bgr to rgb and unpremultiply
for (i = 0; i < pixel_count; ++i) {
unsigned char a = p[3];
unsigned char t = p[0];
if (a) {
unsigned char half = a / 2;
p[0] = (p[2] * 255 + half) / a;
p[1] = (p[1] * 255 + half) / a;
p[2] = (t * 255 + half) / a;
} else {
p[0] = p[2];
p[2] = t;
}
p += 4;
}
} else {
// convert bgr to rgb
for (i = 0; i < pixel_count; ++i) {
unsigned char t = p[0];
p[0] = p[2];
p[2] = t;
p += 4;
}
}
}
}
#define STBI__PNG_TYPE(a, b, c, d) \
(((unsigned)(a) << 24) + ((unsigned)(b) << 16) + ((unsigned)(c) << 8) + \
(unsigned)(d))
static int stbi__parse_png_file(stbi__png *z, int scan, int req_comp) {
unsigned char palette[1024], pal_img_n = 0;
unsigned char has_trans = 0, tc[3] = {0};
uint16_t tc16[3];
uint32_t ioff = 0, idata_limit = 0, i, pal_len = 0;
int first = 1, k, interlace = 0, color = 0, is_iphone = 0;
stbi__context *s = z->s;
z->expanded = NULL;
z->idata = NULL;
z->out = NULL;
if (!stbi__check_png_header(s)) return 0;
if (scan == STBI__SCAN_type) return 1;
for (;;) {
stbi__pngchunk c = stbi__get_chunk_header(s);
switch (c.type) {
case STBI__PNG_TYPE('C', 'g', 'B', 'I'):
is_iphone = 1;
stbi__skip(s, c.length);
break;
case STBI__PNG_TYPE('I', 'H', 'D', 'R'): {
int comp, filter;
if (!first) return stbi__err("multiple IHDR", "Corrupt PNG");
first = 0;
if (c.length != 13) return stbi__err("bad IHDR len", "Corrupt PNG");
s->img_x = stbi__get32be(s);
s->img_y = stbi__get32be(s);
if (s->img_y > STBI_MAX_DIMENSIONS)
return stbi__err("too large", "Very large image (corrupt?)");
if (s->img_x > STBI_MAX_DIMENSIONS)
return stbi__err("too large", "Very large image (corrupt?)");
z->depth = stbi__get8(s);
if (z->depth != 1 && z->depth != 2 && z->depth != 4 && z->depth != 8 &&
z->depth != 16)
return stbi__err("1/2/4/8/16-bit only",
"PNG not supported: 1/2/4/8/16-bit only");
color = stbi__get8(s);
if (color > 6) return stbi__err("bad ctype", "Corrupt PNG");
if (color == 3 && z->depth == 16)
return stbi__err("bad ctype", "Corrupt PNG");
if (color == 3)
pal_img_n = 3;
else if (color & 1)
return stbi__err("bad ctype", "Corrupt PNG");
comp = stbi__get8(s);
if (comp) return stbi__err("bad comp method", "Corrupt PNG");
filter = stbi__get8(s);
if (filter) return stbi__err("bad filter method", "Corrupt PNG");
interlace = stbi__get8(s);
if (interlace > 1)
return stbi__err("bad interlace method", "Corrupt PNG");
if (!s->img_x || !s->img_y)
return stbi__err("0-pixel image", "Corrupt PNG");
if (!pal_img_n) {
s->img_n = (color & 2 ? 3 : 1) + (color & 4 ? 1 : 0);
if ((1 << 30) / s->img_x / s->img_n < s->img_y)
return stbi__err("too large", "Image too large to decode");
} else {
// if paletted, then pal_n is our final components, and
// img_n is # components to decompress/filter.
s->img_n = 1;
if ((1 << 30) / s->img_x / 4 < s->img_y)
return stbi__err("too large", "Corrupt PNG");
}
// even with SCAN_header, have to scan to see if we have a tRNS
break;
}
case STBI__PNG_TYPE('P', 'L', 'T', 'E'): {
if (first) return stbi__err("first not IHDR", "Corrupt PNG");
if (c.length > 256 * 3) return stbi__err("invalid PLTE", "Corrupt PNG");
pal_len = c.length / 3;
if (pal_len * 3 != c.length)
return stbi__err("invalid PLTE", "Corrupt PNG");
for (i = 0; i < pal_len; ++i) {
palette[i * 4 + 0] = stbi__get8(s);
palette[i * 4 + 1] = stbi__get8(s);
palette[i * 4 + 2] = stbi__get8(s);
palette[i * 4 + 3] = 255;
}
break;
}
case STBI__PNG_TYPE('t', 'R', 'N', 'S'): {
if (first) return stbi__err("first not IHDR", "Corrupt PNG");
if (z->idata) return stbi__err("tRNS after IDAT", "Corrupt PNG");
if (pal_img_n) {
if (scan == STBI__SCAN_header) {
s->img_n = 4;
return 1;
}
if (pal_len == 0) return stbi__err("tRNS before PLTE", "Corrupt PNG");
if (c.length > pal_len)
return stbi__err("bad tRNS len", "Corrupt PNG");
pal_img_n = 4;
for (i = 0; i < c.length; ++i) palette[i * 4 + 3] = stbi__get8(s);
} else {
if (!(s->img_n & 1))
return stbi__err("tRNS with alpha", "Corrupt PNG");
if (c.length != (uint32_t)s->img_n * 2)
return stbi__err("bad tRNS len", "Corrupt PNG");
has_trans = 1;
// non-paletted with tRNS = constant alpha.
// if header-scanning, we can stop now.
if (scan == STBI__SCAN_header) {
++s->img_n;
return 1;
}
if (z->depth == 16) {
for (k = 0; k < s->img_n; ++k)
tc16[k] = (uint16_t)stbi__get16be(s); // copy the values as-is
} else {
for (k = 0; k < s->img_n; ++k)
tc[k] = (unsigned char)(stbi__get16be(s) & 255) *
stbi__depth_scale_table[z->depth]; // non 8-bit images
// will be larger
}
}
break;
}
case STBI__PNG_TYPE('I', 'D', 'A', 'T'): {
if (first) return stbi__err("first not IHDR", "Corrupt PNG");
if (pal_img_n && !pal_len) return stbi__err("no PLTE", "Corrupt PNG");
if (scan == STBI__SCAN_header) {
// header scan definitely stops at first IDAT
if (pal_img_n) s->img_n = pal_img_n;
return 1;
}
if (c.length > (1u << 30))
return stbi__err("IDAT size limit",
"IDAT section larger than 2^30 bytes");
if ((int)(ioff + c.length) < (int)ioff) return 0;
if (ioff + c.length > idata_limit) {
unsigned char *p;
if (idata_limit == 0) idata_limit = c.length > 4096 ? c.length : 4096;
while (ioff + c.length > idata_limit) idata_limit *= 2;
p = realloc(z->idata, idata_limit);
if (p == NULL) return stbi__err("outofmem", "Out of memory");
z->idata = p;
}
if (!stbi__getn(s, z->idata + ioff, c.length))
return stbi__err("outofdata", "Corrupt PNG");
ioff += c.length;
break;
}
case STBI__PNG_TYPE('I', 'E', 'N', 'D'): {
uint32_t raw_len, bpl;
if (first) return stbi__err("first not IHDR", "Corrupt PNG");
if (scan != STBI__SCAN_load) return 1;
if (z->idata == NULL) return stbi__err("no IDAT", "Corrupt PNG");
// initial guess for decoded data size to avoid unnecessary reallocs
bpl = (s->img_x * z->depth + 7) / 8; // bytes per line, per component
raw_len = bpl * s->img_y * s->img_n /* pixels */ +
s->img_y /* filter mode per row */;
z->expanded =
(unsigned char *)stbi_zlib_decode_malloc_guesssize_headerflag(
(char *)z->idata, ioff, raw_len, (int *)&raw_len, !is_iphone);
if (z->expanded == NULL) return 0; // zlib should set error
free(z->idata);
z->idata = NULL;
if ((req_comp == s->img_n + 1 && req_comp != 3 && !pal_img_n) ||
has_trans) {
s->img_out_n = s->img_n + 1;
} else {
s->img_out_n = s->img_n;
}
if (!stbi__create_png_image(z, z->expanded, raw_len, s->img_out_n,
z->depth, color, interlace))
return 0;
if (has_trans) {
if (z->depth == 16) {
if (!stbi__compute_transparency16(z, tc16, s->img_out_n)) return 0;
} else {
if (!stbi__compute_transparency(z, tc, s->img_out_n)) return 0;
}
}
if (is_iphone && stbi__de_iphone_flag && s->img_out_n > 2)
stbi__de_iphone(z);
if (pal_img_n) {
// pal_img_n == 3 or 4
s->img_n = pal_img_n; // record the actual colors we had
s->img_out_n = pal_img_n;
if (req_comp >= 3) s->img_out_n = req_comp;
if (!stbi__expand_png_palette(z, palette, pal_len, s->img_out_n))
return 0;
} else if (has_trans) {
// non-paletted image with tRNS -> source image has (constant) alpha
++s->img_n;
}
free(z->expanded);
z->expanded = NULL;
// end of PNG chunk, read and skip CRC
stbi__get32be(s);
return 1;
}
default:
// if critical, fail
if (first) return stbi__err("first not IHDR", "Corrupt PNG");
if ((c.type & (1 << 29)) == 0) {
#if !defined(STBI_NO_FAILURE_STRINGS) && !defined(STBI_FAILURE_USERMSG)
// not threadsafe
static char invalid_chunk[] = "XXXX PNG chunk not known";
invalid_chunk[0] = STBI__BYTECAST(c.type >> 24);
invalid_chunk[1] = STBI__BYTECAST(c.type >> 16);
invalid_chunk[2] = STBI__BYTECAST(c.type >> 8);
invalid_chunk[3] = STBI__BYTECAST(c.type >> 0);
#endif
return stbi__err(invalid_chunk,
"PNG not supported: unknown PNG chunk type");
}
stbi__skip(s, c.length);
break;
}
// end of PNG chunk, read and skip CRC
stbi__get32be(s);
}
}
static void *stbi__do_png(stbi__png *p, int *x, int *y, int *n, int req_comp,
stbi__result_info *ri) {
void *result = NULL;
if (req_comp < 0 || req_comp > 4)
return stbi__errpuc("bad req_comp", "Internal error");
if (stbi__parse_png_file(p, STBI__SCAN_load, req_comp)) {
if (p->depth <= 8)
ri->bits_per_channel = 8;
else if (p->depth == 16)
ri->bits_per_channel = 16;
else
return stbi__errpuc("bad bits_per_channel",
"PNG not supported: unsupported color depth");
result = p->out;
p->out = NULL;
if (req_comp && req_comp != p->s->img_out_n) {
if (ri->bits_per_channel == 8)
result = stbi__convert_format((unsigned char *)result, p->s->img_out_n,
req_comp, p->s->img_x, p->s->img_y);
else
result = stbi__convert_format16((uint16_t *)result, p->s->img_out_n,
req_comp, p->s->img_x, p->s->img_y);
p->s->img_out_n = req_comp;
if (result == NULL) return result;
}
*x = p->s->img_x;
*y = p->s->img_y;
if (n) *n = p->s->img_n;
}
free(p->out);
p->out = NULL;
free(p->expanded);
p->expanded = NULL;
free(p->idata);
p->idata = NULL;
return result;
}
static dontinline void *stbi__png_load(stbi__context *s, int *x, int *y,
int *comp, int req_comp,
stbi__result_info *ri) {
stbi__png p;
p.s = s;
return stbi__do_png(&p, x, y, comp, req_comp, ri);
}
static int stbi__png_test(stbi__context *s) {
int r;
r = stbi__check_png_header(s);
stbi__rewind(s);
return r;
}
static int stbi__png_info_raw(stbi__png *p, int *x, int *y, int *comp) {
if (!stbi__parse_png_file(p, STBI__SCAN_header, 0)) {
stbi__rewind(p->s);
return 0;
}
if (x) *x = p->s->img_x;
if (y) *y = p->s->img_y;
if (comp) *comp = p->s->img_n;
return 1;
}
static int stbi__png_info(stbi__context *s, int *x, int *y, int *comp) {
stbi__png p;
p.s = s;
return stbi__png_info_raw(&p, x, y, comp);
}
static int stbi__png_is16(stbi__context *s) {
stbi__png p;
p.s = s;
if (!stbi__png_info_raw(&p, NULL, NULL, NULL)) return 0;
if (p.depth != 16) {
stbi__rewind(p.s);
return 0;
}
return 1;
}
// *****************************************************************************
// GIF loader -- public domain by Jean-Marc Lienher -- simplified/shrunk by
// stb
typedef struct {
int16_t prefix;
unsigned char first;
unsigned char suffix;
} stbi__gif_lzw;
typedef struct {
int w, h;
unsigned char *out; // output buffer (always 4 components)
unsigned char
*background; // The current "background" as far as a gif is concerned
unsigned char *history;
int flags, bgindex, ratio, transparent, eflags;
unsigned char pal[256][4];
unsigned char lpal[256][4];
stbi__gif_lzw codes[8192];
unsigned char *color_table;
int parse, step;
int lflags;
int start_x, start_y;
int max_x, max_y;
int cur_x, cur_y;
int line_size;
int delay;
} stbi__gif;
static int stbi__gif_test_raw(stbi__context *s) {
int sz;
if (stbi__get8(s) != 'G' || stbi__get8(s) != 'I' || stbi__get8(s) != 'F' ||
stbi__get8(s) != '8')
return 0;
sz = stbi__get8(s);
if (sz != '9' && sz != '7') return 0;
if (stbi__get8(s) != 'a') return 0;
return 1;
}
static int stbi__gif_test(stbi__context *s) {
int r = stbi__gif_test_raw(s);
stbi__rewind(s);
return r;
}
static void stbi__gif_parse_colortable(stbi__context *s,
unsigned char pal[256][4],
int num_entries, int transp) {
int i;
for (i = 0; i < num_entries; ++i) {
pal[i][2] = stbi__get8(s);
pal[i][1] = stbi__get8(s);
pal[i][0] = stbi__get8(s);
pal[i][3] = transp == i ? 0 : 255;
}
}
static int stbi__gif_header(stbi__context *s, stbi__gif *g, int *comp,
int is_info) {
unsigned char version;
if (stbi__get8(s) != 'G' || stbi__get8(s) != 'I' || stbi__get8(s) != 'F' ||
stbi__get8(s) != '8')
return stbi__err("not GIF", "Corrupt GIF");
version = stbi__get8(s);
if (version != '7' && version != '9') {
return stbi__err("not GIF", "Corrupt GIF");
}
if (stbi__get8(s) != 'a') return stbi__err("not GIF", "Corrupt GIF");
stbi__g_failure_reason = "";
g->w = stbi__get16le(s);
g->h = stbi__get16le(s);
g->flags = stbi__get8(s);
g->bgindex = stbi__get8(s);
g->ratio = stbi__get8(s);
g->transparent = -1;
if (g->w > STBI_MAX_DIMENSIONS)
return stbi__err("too large", "Very large image (corrupt?)");
if (g->h > STBI_MAX_DIMENSIONS)
return stbi__err("too large", "Very large image (corrupt?)");
if (comp != 0) {
*comp = 4; // can't actually tell whether it's 3 or 4 until we parse the
// comments
}
if (is_info) return 1;
if (g->flags & 0x80) {
stbi__gif_parse_colortable(s, g->pal, 2 << (g->flags & 7), -1);
}
return 1;
}
static int stbi__gif_info_raw(stbi__context *s, int *x, int *y, int *comp) {
stbi__gif *g = (stbi__gif *)malloc(sizeof(stbi__gif));
if (!g) return stbi__err("outofmem", "Out of memory");
if (!stbi__gif_header(s, g, comp, 1)) {
free(g);
stbi__rewind(s);
return 0;
}
if (x) *x = g->w;
if (y) *y = g->h;
free(g);
return 1;
}
static void stbi__out_gif_code(stbi__gif *g, uint16_t code) {
unsigned char *p, *c;
int idx;
// recurse to decode the prefixes, since the linked-list is backwards,
// and working backwards through an interleaved image would be nasty
if (g->codes[code].prefix >= 0) stbi__out_gif_code(g, g->codes[code].prefix);
if (g->cur_y >= g->max_y) return;
idx = g->cur_x + g->cur_y;
p = &g->out[idx];
g->history[idx / 4] = 1;
c = &g->color_table[g->codes[code].suffix * 4];
if (c[3] > 128) { // don't render transparent pixels;
p[0] = c[2];
p[1] = c[1];
p[2] = c[0];
p[3] = c[3];
}
g->cur_x += 4;
if (g->cur_x >= g->max_x) {
g->cur_x = g->start_x;
g->cur_y += g->step;
while (g->cur_y >= g->max_y && g->parse > 0) {
g->step = (1 << g->parse) * g->line_size;
g->cur_y = g->start_y + (g->step >> 1);
--g->parse;
}
}
}
static unsigned char *stbi__process_gif_raster(stbi__context *s, stbi__gif *g) {
unsigned char lzw_cs;
int32_t len, init_code;
uint32_t first;
int32_t codesize, codemask, avail, oldcode, bits, valid_bits, clear;
stbi__gif_lzw *p;
lzw_cs = stbi__get8(s);
if (lzw_cs > 12) return NULL;
clear = 1 << lzw_cs;
first = 1;
codesize = lzw_cs + 1;
codemask = (1 << codesize) - 1;
bits = 0;
valid_bits = 0;
for (init_code = 0; init_code < clear; init_code++) {
g->codes[init_code].prefix = -1;
g->codes[init_code].first = (unsigned char)init_code;
g->codes[init_code].suffix = (unsigned char)init_code;
}
// support no starting clear code
avail = clear + 2;
oldcode = -1;
len = 0;
for (;;) {
if (valid_bits < codesize) {
if (len == 0) {
len = stbi__get8(s); // start new block
if (len == 0) return g->out;
}
--len;
bits |= (int32_t)stbi__get8(s) << valid_bits;
valid_bits += 8;
} else {
int32_t code = bits & codemask;
bits >>= codesize;
valid_bits -= codesize;
// @OPTIMIZE: is there some way we can accelerate the non-clear path?
if (code == clear) { // clear code
codesize = lzw_cs + 1;
codemask = (1 << codesize) - 1;
avail = clear + 2;
oldcode = -1;
first = 0;
} else if (code == clear + 1) { // end of stream code
stbi__skip(s, len);
while ((len = stbi__get8(s)) > 0) stbi__skip(s, len);
return g->out;
} else if (code <= avail) {
if (first) {
return stbi__errpuc("no clear code", "Corrupt GIF");
}
if (oldcode >= 0) {
p = &g->codes[avail++];
if (avail > 8192) {
return stbi__errpuc("too many codes", "Corrupt GIF");
}
p->prefix = (int16_t)oldcode;
p->first = g->codes[oldcode].first;
p->suffix = (code == avail) ? p->first : g->codes[code].first;
} else if (code == avail)
return stbi__errpuc("illegal code in raster", "Corrupt GIF");
stbi__out_gif_code(g, (uint16_t)code);
if ((avail & codemask) == 0 && avail <= 0x0FFF) {
codesize++;
codemask = (1 << codesize) - 1;
}
oldcode = code;
} else {
return stbi__errpuc("illegal code in raster", "Corrupt GIF");
}
}
}
}
// this function is designed to support animated gifs, although stb_image
// doesn't support it two back is the image from two frames ago, used for a
// very specific disposal format
static unsigned char *stbi__gif_load_next(stbi__context *s, stbi__gif *g,
int *comp, int req_comp,
unsigned char *two_back) {
int dispose;
int first_frame;
int pi;
int pcount;
// on first frame, any non-written pixels get the background colour
// (non-transparent)
first_frame = 0;
if (g->out == 0) {
if (!stbi__gif_header(s, g, comp, 0))
return 0; // stbi__g_failure_reason set by stbi__gif_header
if (!stbi__mad3sizes_valid(4, g->w, g->h, 0))
return stbi__errpuc("too large", "GIF image is too large");
pcount = g->w * g->h;
g->out = malloc(4 * pcount);
g->background = malloc(4 * pcount);
g->history = malloc(pcount);
if (!g->out || !g->background || !g->history)
return stbi__errpuc("outofmem", "Out of memory");
// image is treated as "transparent" at the start - i.e. nothing overwrites
// the current background; background colour is only used for pixels that
// are not rendered first frame, after that "background" color refers to
// the color that was there the previous frame.
bzero(g->out, 4 * pcount);
bzero(g->background,
4 * pcount); // state of the background (starts transparent)
bzero(g->history,
pcount); // pixels that were affected previous frame
first_frame = 1;
} else {
// second frame - how do we dispose of the previous one?
dispose = (g->eflags & 0x1C) >> 2;
pcount = g->w * g->h;
if ((dispose == 3) && (two_back == 0)) {
dispose = 2; // if I don't have an image to revert back to, default to
// the old background
}
if (dispose == 3) { // use previous graphic
for (pi = 0; pi < pcount; ++pi) {
if (g->history[pi]) {
memcpy(&g->out[pi * 4], &two_back[pi * 4], 4);
}
}
} else if (dispose == 2) {
// restore what was changed last frame to background before that frame;
for (pi = 0; pi < pcount; ++pi) {
if (g->history[pi]) {
memcpy(&g->out[pi * 4], &g->background[pi * 4], 4);
}
}
} else {
// This is a non-disposal case either way, so just
// leave the pixels as is, and they will become the new background
// 1: do not dispose
// 0: not specified.
}
// background is what out is after the undoing of the previou frame;
memcpy(g->background, g->out, 4 * g->w * g->h);
}
// clear my history;
bzero(g->history,
g->w * g->h); // pixels that were affected previous frame
for (;;) {
int tag = stbi__get8(s);
switch (tag) {
case 0x2C: /* Image Descriptor */
{
int32_t x, y, w, h;
unsigned char *o;
x = stbi__get16le(s);
y = stbi__get16le(s);
w = stbi__get16le(s);
h = stbi__get16le(s);
if (((x + w) > (g->w)) || ((y + h) > (g->h)))
return stbi__errpuc("bad Image Descriptor", "Corrupt GIF");
g->line_size = g->w * 4;
g->start_x = x * 4;
g->start_y = y * g->line_size;
g->max_x = g->start_x + w * 4;
g->max_y = g->start_y + h * g->line_size;
g->cur_x = g->start_x;
g->cur_y = g->start_y;
// if the width of the specified rectangle is 0, that means
// we may not see *any* pixels or the image is malformed;
// to make sure this is caught, move the current y down to
// max_y (which is what out_gif_code checks).
if (w == 0) g->cur_y = g->max_y;
g->lflags = stbi__get8(s);
if (g->lflags & 0x40) {
g->step = 8 * g->line_size; // first interlaced spacing
g->parse = 3;
} else {
g->step = g->line_size;
g->parse = 0;
}
if (g->lflags & 0x80) {
stbi__gif_parse_colortable(s, g->lpal, 2 << (g->lflags & 7),
g->eflags & 0x01 ? g->transparent : -1);
g->color_table = (unsigned char *)g->lpal;
} else if (g->flags & 0x80) {
g->color_table = (unsigned char *)g->pal;
} else
return stbi__errpuc("missing color table", "Corrupt GIF");
o = stbi__process_gif_raster(s, g);
if (!o) return NULL;
// if this was the first frame,
pcount = g->w * g->h;
if (first_frame && (g->bgindex > 0)) {
// if first frame, any pixel not drawn to gets the background color
for (pi = 0; pi < pcount; ++pi) {
if (g->history[pi] == 0) {
g->pal[g->bgindex][3] =
255; // just in case it was made transparent, undo that; It
// will be reset next frame if need be;
memcpy(&g->out[pi * 4], &g->pal[g->bgindex], 4);
}
}
}
return o;
}
case 0x21: // Comment Extension.
{
int len;
int ext = stbi__get8(s);
if (ext == 0xF9) { // Graphic Control Extension.
len = stbi__get8(s);
if (len == 4) {
g->eflags = stbi__get8(s);
g->delay =
10 *
stbi__get16le(
s); // delay - 1/100th of a second, saving as 1/1000ths.
// unset old transparent
if (g->transparent >= 0) {
g->pal[g->transparent][3] = 255;
}
if (g->eflags & 0x01) {
g->transparent = stbi__get8(s);
if (g->transparent >= 0) {
g->pal[g->transparent][3] = 0;
}
} else {
// don't need transparent
stbi__skip(s, 1);
g->transparent = -1;
}
} else {
stbi__skip(s, len);
break;
}
}
while ((len = stbi__get8(s)) != 0) {
stbi__skip(s, len);
}
break;
}
case 0x3B: // gif stream termination code
return (
unsigned char *)s; // using '1' causes warning on some compilers
default:
return stbi__errpuc("unknown code", "Corrupt GIF");
}
}
}
static void *stbi__load_gif_main_outofmem(stbi__gif *g, unsigned char *out,
int **delays) {
free(g->out);
free(g->history);
free(g->background);
if (out) free(out);
if (delays && *delays) free(*delays);
return stbi__errpuc("outofmem", "Out of memory");
}
static void *stbi__load_gif_main(stbi__context *s, int **delays, int *x, int *y,
int *z, int *comp, int req_comp) {
if (stbi__gif_test(s)) {
int layers = 0;
unsigned char *u = 0;
unsigned char *out = 0;
unsigned char *two_back = 0;
stbi__gif *g;
int stride;
g = calloc(1, sizeof(stbi__gif));
if (delays) {
*delays = 0;
}
do {
u = stbi__gif_load_next(s, g, comp, req_comp, two_back);
if (u == (unsigned char *)s) u = 0; // end of animated gif marker
if (u) {
*x = g->w;
*y = g->h;
++layers;
stride = g->w * g->h * 4;
if (out) {
void *tmp = (unsigned char *)realloc(out, layers * stride);
if (!tmp)
return stbi__load_gif_main_outofmem(g, out, delays);
else {
out = (unsigned char *)tmp;
}
if (delays) {
int *new_delays = (int *)realloc(*delays, sizeof(int) * layers);
if (!new_delays)
return stbi__load_gif_main_outofmem(g, out, delays);
*delays = new_delays;
}
} else {
out = malloc(layers * stride);
if (!out) return stbi__load_gif_main_outofmem(g, out, delays);
if (delays) {
*delays = malloc(layers * sizeof(int));
if (!*delays) return stbi__load_gif_main_outofmem(g, out, delays);
}
}
memcpy(out + ((layers - 1) * stride), u, stride);
if (layers >= 2) {
two_back = out + ((layers - 2) * stride);
}
if (delays) {
(*delays)[layers - 1U] = g->delay;
}
}
} while (u != 0);
free(g->out);
free(g->history);
free(g->background);
// do the final conversion after loading everything;
if (req_comp && req_comp != 4)
out = stbi__convert_format(out, 4, req_comp, layers * g->w, g->h);
free(g);
*z = layers;
return out;
} else {
return stbi__errpuc("not GIF", "Image was not as a gif type.");
}
}
static dontinline void *stbi__gif_load(stbi__context *s, int *x, int *y,
int *comp, int req_comp,
stbi__result_info *ri) {
unsigned char *u = 0;
stbi__gif *g;
g = calloc(1, sizeof(stbi__gif));
u = stbi__gif_load_next(s, g, comp, req_comp, 0);
if (u == (unsigned char *)s) u = 0; // end of animated gif marker
if (u) {
*x = g->w;
*y = g->h;
// moved conversion to after successful load so that the same
// can be done for multiple frames.
if (req_comp && req_comp != 4)
u = stbi__convert_format(u, 4, req_comp, g->w, g->h);
} else if (g->out) {
// if there was an error and we allocated an image buffer, free it!
free(g->out);
}
// free buffers needed for multiple frame loading;
free(g->history);
free(g->background);
free(g);
return u;
}
static int stbi__gif_info(stbi__context *s, int *x, int *y, int *comp) {
return stbi__gif_info_raw(s, x, y, comp);
}
// ********************************************************************
// Portable Gray Map and Portable Pixel Map loader
// by Ken Miller
//
// PGM: http://netpbm.sourceforge.net/doc/pgm.html
// PPM: http://netpbm.sourceforge.net/doc/ppm.html
//
// Known limitations:
// Does not support comments in the header section
// Does not support ASCII image data (formats P2 and P3)
static int stbi__pnm_test(stbi__context *s) {
char p, t;
p = (char)stbi__get8(s);
t = (char)stbi__get8(s);
if (p != 'P' || (t != '5' && t != '6')) {
stbi__rewind(s);
return 0;
}
return 1;
}
static dontinline void *stbi__pnm_load(stbi__context *s, int *x, int *y,
int *comp, int req_comp,
stbi__result_info *ri) {
unsigned char *out;
ri->bits_per_channel =
stbi__pnm_info(s, (int *)&s->img_x, (int *)&s->img_y, (int *)&s->img_n);
if (ri->bits_per_channel == 0) return 0;
if (s->img_y > STBI_MAX_DIMENSIONS) {
return stbi__errpuc("too large", "Very large image (corrupt?)");
}
if (s->img_x > STBI_MAX_DIMENSIONS) {
return stbi__errpuc("too large", "Very large image (corrupt?)");
}
*x = s->img_x;
*y = s->img_y;
if (comp) *comp = s->img_n;
if (!stbi__mad4sizes_valid(s->img_n, s->img_x, s->img_y,
ri->bits_per_channel / 8, 0)) {
return stbi__errpuc("too large", "PNM too large");
}
out = stbi__malloc_mad4(s->img_n, s->img_x, s->img_y,
ri->bits_per_channel / 8, 0);
if (!stbi__getn(
s, out,
s->img_n * s->img_x * s->img_y * (ri->bits_per_channel / 8))) {
free(out);
return stbi__errpuc("bad PNM", "PNM file truncated");
}
if (req_comp && req_comp != s->img_n) {
if (ri->bits_per_channel == 16) {
out = (unsigned char *)stbi__convert_format16(
(uint16_t *)out, s->img_n, req_comp, s->img_x, s->img_y);
} else {
out = stbi__convert_format(out, s->img_n, req_comp, s->img_x, s->img_y);
}
if (out == NULL) return out; // stbi__convert_format frees input on failure
}
return out;
}
static int stbi__pnm_isspace(char c) {
return c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' ||
c == '\r';
}
static void stbi__pnm_skip_whitespace(stbi__context *s, char *c) {
for (;;) {
while (!stbi__at_eof(s) && stbi__pnm_isspace(*c)) *c = (char)stbi__get8(s);
if (stbi__at_eof(s) || *c != '#') break;
while (!stbi__at_eof(s) && *c != '\n' && *c != '\r')
*c = (char)stbi__get8(s);
}
}
static int stbi__pnm_isdigit(char c) {
return c >= '0' && c <= '9';
}
static int stbi__pnm_getinteger(stbi__context *s, char *c) {
int value = 0;
while (!stbi__at_eof(s) && stbi__pnm_isdigit(*c)) {
value = value * 10 + (*c - '0');
*c = (char)stbi__get8(s);
// TODO INT_MAX
if ((value > 214748364) || (value == 214748364 && *c > '7')) {
return stbi__err(
"integer parse overflow",
"Parsing an integer in the PPM header overflowed a 32-bit int");
}
}
return value;
}
static int stbi__pnm_info(stbi__context *s, int *x, int *y, int *comp) {
int maxv, dummy;
char c, p, t;
if (!x) x = &dummy;
if (!y) y = &dummy;
if (!comp) comp = &dummy;
stbi__rewind(s);
// Get identifier
p = (char)stbi__get8(s);
t = (char)stbi__get8(s);
if (p != 'P' || (t != '5' && t != '6')) {
stbi__rewind(s);
return 0;
}
*comp =
(t == '6') ? 3 : 1; // '5' is 1-component .pgm; '6' is 3-component .ppm
c = (char)stbi__get8(s);
stbi__pnm_skip_whitespace(s, &c);
*x = stbi__pnm_getinteger(s, &c); // read width
if (*x == 0) {
return stbi__err("invalid_width",
"PPM image header had zero or overflowing width");
}
stbi__pnm_skip_whitespace(s, &c);
*y = stbi__pnm_getinteger(s, &c); // read height
if (*y == 0) {
return stbi__err("invalid height",
"PPM image header had zero or overflowing height");
}
stbi__pnm_skip_whitespace(s, &c);
maxv = stbi__pnm_getinteger(s, &c); // read max value
if (maxv > 65535)
return stbi__err("max value > 65535",
"PPM image supports only 8-bit and 16-bit images");
else if (maxv > 255)
return 16;
else
return 8;
}
static int stbi__pnm_is16(stbi__context *s) {
if (stbi__pnm_info(s, NULL, NULL, NULL) == 16) return 1;
return 0;
}
static int stbi__info_main(stbi__context *s, int *x, int *y, int *comp) {
#ifndef STBI_NO_JPEG
if (stbi__jpeg_info(s, x, y, comp)) return 1;
#endif
#ifndef STBI_NO_PNG
if (stbi__png_info(s, x, y, comp)) return 1;
#endif
#ifndef STBI_NO_GIF
if (stbi__gif_info(s, x, y, comp)) return 1;
#endif
#ifndef STBI_NO_PNM
if (stbi__pnm_info(s, x, y, comp)) return 1;
#endif
return stbi__err("unknown image type",
"Image not of any known type, or corrupt");
}
static int stbi__is_16_main(stbi__context *s) {
#ifndef STBI_NO_PNG
if (stbi__png_is16(s)) return 1;
#endif
#ifndef STBI_NO_PNM
if (stbi__pnm_is16(s)) return 1;
#endif
return 0;
}
int stbi_info(char const *filename, int *x, int *y, int *comp) {
FILE *f = stbi__fopen(filename, "rb");
int result;
if (!f) return stbi__err("can't fopen", "Unable to open file");
result = stbi_info_from_file(f, x, y, comp);
fclose(f);
return result;
}
int stbi_info_from_file(FILE *f, int *x, int *y, int *comp) {
int r;
stbi__context s;
long pos = ftell(f);
if (pos < 0) return stbi__err("bad file", "ftell() failed");
stbi__start_file(&s, f);
r = stbi__info_main(&s, x, y, comp);
if (fseek(f, pos, SEEK_SET)) return stbi__err("bad file", "fseek() failed");
return r;
}
int stbi_is_16_bit(char const *filename) {
FILE *f = stbi__fopen(filename, "rb");
int result;
if (!f) return stbi__err("can't fopen", "Unable to open file");
result = stbi_is_16_bit_from_file(f);
fclose(f);
return result;
}
int stbi_is_16_bit_from_file(FILE *f) {
int r;
stbi__context s;
long pos = ftell(f);
if (pos < 0) return stbi__err("bad file", "ftell() failed");
stbi__start_file(&s, f);
r = stbi__is_16_main(&s);
if (fseek(f, pos, SEEK_SET)) return stbi__err("bad file", "fseek() failed");
return r;
}
int stbi_info_from_memory(unsigned char const *buffer, int len, int *x, int *y,
int *comp) {
stbi__context s;
stbi__start_mem(&s, buffer, len);
return stbi__info_main(&s, x, y, comp);
}
int stbi_info_from_callbacks(stbi_io_callbacks const *c, void *user, int *x,
int *y, int *comp) {
stbi__context s;
stbi__start_callbacks(&s, (stbi_io_callbacks *)c, user);
return stbi__info_main(&s, x, y, comp);
}
int stbi_is_16_bit_from_memory(unsigned char const *buffer, int len) {
stbi__context s;
stbi__start_mem(&s, buffer, len);
return stbi__is_16_main(&s);
}
int stbi_is_16_bit_from_callbacks(stbi_io_callbacks const *c, void *user) {
stbi__context s;
stbi__start_callbacks(&s, (stbi_io_callbacks *)c, user);
return stbi__is_16_main(&s);
}
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