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61 lines
1.6 KiB
C
61 lines
1.6 KiB
C
/*
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* cmyk.h
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*
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* Copyright (C) 2017-2018, 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 "jconfigint.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(JSAMPLE r, JSAMPLE g, JSAMPLE b, JSAMPLE *c, JSAMPLE *m,
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JSAMPLE *y, JSAMPLE *k)
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{
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double ctmp = 1.0 - ((double)r / 255.0);
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double mtmp = 1.0 - ((double)g / 255.0);
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double ytmp = 1.0 - ((double)b / 255.0);
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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)(255.0 - ctmp * 255.0 + 0.5);
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*m = (JSAMPLE)(255.0 - mtmp * 255.0 + 0.5);
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*y = (JSAMPLE)(255.0 - ytmp * 255.0 + 0.5);
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*k = (JSAMPLE)(255.0 - ktmp * 255.0 + 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(JSAMPLE c, JSAMPLE m, JSAMPLE y, JSAMPLE k, JSAMPLE *r, JSAMPLE *g,
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JSAMPLE *b)
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{
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*r = (JSAMPLE)((double)c * (double)k / 255.0 + 0.5);
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*g = (JSAMPLE)((double)m * (double)k / 255.0 + 0.5);
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*b = (JSAMPLE)((double)y * (double)k / 255.0 + 0.5);
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}
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#endif /* CMYK_H */
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