/* * Copyright (c) 1988-1997 Sam Leffler * Copyright (c) 1991-1997 Silicon Graphics, Inc. * * Permission to use, copy, modify, distribute, and sell this software and * its documentation for any purpose is hereby granted without fee, provided * that (i) the above copyright notices and this permission notice appear in * all copies of the software and related documentation, and (ii) the names of * Sam Leffler and Silicon Graphics may not be used in any advertising or * publicity relating to the software without the specific, prior written * permission of Sam Leffler and Silicon Graphics. * * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. * * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE * OF THIS SOFTWARE. */ /* * CIE L*a*b* to CIE XYZ and CIE XYZ to RGB conversion routines are taken * from the VIPS library (http://www.vips.ecs.soton.ac.uk) with * the permission of John Cupitt, the VIPS author. */ /* * TIFF Library. * * Color space conversion routines. */ #include "tiffiop.h" #include <math.h> /* * Convert color value from the CIE L*a*b* 1976 space to CIE XYZ. */ void TIFFCIELabToXYZ(TIFFCIELabToRGB *cielab, uint32_t l, int32_t a, int32_t b, float *X, float *Y, float *Z) { … } /* * For CIELab encoded in 16 bits, L is an unsigned integer range [0,65535]. * The a* and b* components are signed integers range [-32768,32767]. The 16 * bit chrominance values are encoded as 256 times the 1976 CIE a* and b* * values */ void TIFFCIELab16ToXYZ(TIFFCIELabToRGB *cielab, uint32_t l, int32_t a, int32_t b, float *X, float *Y, float *Z) { … } #define RINT … /* * Convert color value from the XYZ space to RGB. */ void TIFFXYZToRGB(TIFFCIELabToRGB *cielab, float X, float Y, float Z, uint32_t *r, uint32_t *g, uint32_t *b) { … } #undef RINT /* * Allocate conversion state structures and make look_up tables for * the Yr,Yb,Yg <=> r,g,b conversions. */ int TIFFCIELabToRGBInit(TIFFCIELabToRGB *cielab, const TIFFDisplay *display, float *refWhite) { … } /* * Convert color value from the YCbCr space to RGB. * The colorspace conversion algorithm comes from the IJG v5a code; * see below for more information on how it works. */ #define SHIFT … #define FIX … #define ONE_HALF … #define Code2V … /* !((f)>=(min)) written that way to deal with NaN */ #define CLAMP … #define HICLAMP … void TIFFYCbCrtoRGB(TIFFYCbCrToRGB *ycbcr, uint32_t Y, int32_t Cb, int32_t Cr, uint32_t *r, uint32_t *g, uint32_t *b) { … } /* Clamp function for sanitization purposes. Normally clamping should not */ /* occur for well behaved chroma and refBlackWhite coefficients */ static float CLAMPw(float v, float vmin, float vmax) { … } /* * Initialize the YCbCr->RGB conversion tables. The conversion * is done according to the 6.0 spec: * * R = Y + Cr*(2 - 2*LumaRed) * B = Y + Cb*(2 - 2*LumaBlue) * G = Y * - LumaBlue*Cb*(2-2*LumaBlue)/LumaGreen * - LumaRed*Cr*(2-2*LumaRed)/LumaGreen * * To avoid floating point arithmetic the fractional constants that * come out of the equations are represented as fixed point values * in the range 0...2^16. We also eliminate multiplications by * pre-calculating possible values indexed by Cb and Cr (this code * assumes conversion is being done for 8-bit samples). */ int TIFFYCbCrToRGBInit(TIFFYCbCrToRGB *ycbcr, float *luma, float *refBlackWhite) { … } #undef HICLAMP #undef CLAMP #undef Code2V #undef SHIFT #undef ONE_HALF #undef FIX
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