34 lines
857 B
C
34 lines
857 B
C
#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_ */
|