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Justine Tunney 2020-06-15 07:18:57 -07:00
commit c91b3c5006
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dsp/core/c161.h Normal file
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#ifndef COSMOPOLITAN_DSP_CORE_C161_H_
#define COSMOPOLITAN_DSP_CORE_C161_H_
#include "libc/macros.h"
#if !(__ASSEMBLER__ + __LINKER__ + 0)
#define EXTRA_SHARP 2
/**
* Byte sized kernel for restoring sharpness of resampled memory.
*
* @define CLAMP[(-1*𝑎 + 6*𝑏 + -1*𝑐) / (-1 + 6 + -1)]
* @limit [0..255] → [-510..1,532] → [-127..383] → [0..255]
* @see C1331()
*/
forceinline pureconst artificial unsigned char C161(unsigned char al,
unsigned char bl,
unsigned char cl) {
short ax, bx, cx;
ax = al;
bx = bl;
cx = cl;
ax *= -1;
bx *= +6;
cx *= -1;
ax += bx;
ax += cx;
ax += 2;
ax >>= 2;
return MIN(255, MAX(0, ax));
}
#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
#endif /* COSMOPOLITAN_DSP_CORE_C161_H_ */