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/*
* cmyk.h
*
* Copyright (C) 2017-2018, 2022, 2024, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
* This file contains convenience functions for performing quick & dirty
* CMYK<->RGB conversion. This algorithm is suitable for testing purposes
* only. Properly converting between CMYK and RGB requires a color management
* system.
*/
#ifndef CMYK_H
#define CMYK_H
#include <jinclude.h>
#define JPEG_INTERNALS
#include <jpeglib.h>
#include "jsamplecomp.h"
/* Fully reversible */
INLINE
LOCAL(void)
rgb_to_cmyk(int maxval, _JSAMPLE r, _JSAMPLE g, _JSAMPLE b,
_JSAMPLE *c, _JSAMPLE *m, _JSAMPLE *y, _JSAMPLE *k)
{
double ctmp = 1.0 - ((double)r / (double)maxval);
double mtmp = 1.0 - ((double)g / (double)maxval);
double ytmp = 1.0 - ((double)b / (double)maxval);
double ktmp = MIN(MIN(ctmp, mtmp), ytmp);
if (ktmp == 1.0) ctmp = mtmp = ytmp = 0.0;
else {
ctmp = (ctmp - ktmp) / (1.0 - ktmp);
mtmp = (mtmp - ktmp) / (1.0 - ktmp);
ytmp = (ytmp - ktmp) / (1.0 - ktmp);
}
*c = (_JSAMPLE)((double)maxval - ctmp * (double)maxval + 0.5);
*m = (_JSAMPLE)((double)maxval - mtmp * (double)maxval + 0.5);
*y = (_JSAMPLE)((double)maxval - ytmp * (double)maxval + 0.5);
*k = (_JSAMPLE)((double)maxval - ktmp * (double)maxval + 0.5);
}
/* Fully reversible only for C/M/Y/K values generated with rgb_to_cmyk() */
INLINE
LOCAL(void)
cmyk_to_rgb(int maxval, _JSAMPLE c, _JSAMPLE m, _JSAMPLE y, _JSAMPLE k,
_JSAMPLE *r, _JSAMPLE *g, _JSAMPLE *b)
{
*r = (_JSAMPLE)((double)c * (double)k / (double)maxval + 0.5);
*g = (_JSAMPLE)((double)m * (double)k / (double)maxval + 0.5);
*b = (_JSAMPLE)((double)y * (double)k / (double)maxval + 0.5);
}
#endif /* CMYK_H */
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