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34 lines
857 B
C
34 lines
857 B
C
#ifndef COSMOPOLITAN_DSP_CORE_C161_H_
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#define COSMOPOLITAN_DSP_CORE_C161_H_
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#include "libc/macros.h"
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#if !(__ASSEMBLER__ + __LINKER__ + 0)
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#define EXTRA_SHARP 2
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/**
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* Byte sized kernel for restoring sharpness of resampled memory.
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*
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* @define CLAMP[(-1*𝑎 + 6*𝑏 + -1*𝑐) / (-1 + 6 + -1)]
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* @limit [0..255] → [-510..1,532] → [-127..383] → [0..255]
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* @see C1331()
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*/
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forceinline pureconst artificial unsigned char C161(unsigned char al,
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unsigned char bl,
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unsigned char cl) {
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short ax, bx, cx;
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ax = al;
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bx = bl;
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cx = cl;
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ax *= -1;
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bx *= +6;
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cx *= -1;
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ax += bx;
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ax += cx;
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ax += 2;
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ax >>= 2;
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return MIN(255, MAX(0, ax));
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}
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#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
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#endif /* COSMOPOLITAN_DSP_CORE_C161_H_ */
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