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