41 lines
899 B
C
41 lines
899 B
C
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/*-
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* sRGB.h
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*
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* Utility file; not actually a header, this contains definitions of sRGB
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* calculation functions for inclusion in those test programs that need them.
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*
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* All routines take and return a floating point value in the range 0 to 1.0,
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* doing a calculation according to the sRGB specification. (In fact the source
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* of the numbers is the wikipedia article.)
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*/
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static double
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sRGB_from_linear(double l)
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{
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if (l <= 0.0031308)
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l *= 12.92;
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else
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l = 1.055 * pow(l, 1/2.4) - 0.055;
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return l;
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}
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static double
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linear_from_sRGB(double s)
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{
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if (s <= 0.04045)
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return s / 12.92;
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else
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return pow((s+0.055)/1.055, 2.4);
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}
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static double
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YfromRGB(double r, double g, double b)
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{
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/* Use the sRGB (rounded) coefficients for Rlinear, Glinear, Blinear to get
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* the CIE Y value (also linear).
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*/
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return 0.2126 * r + 0.7152 * g + 0.0722 * b;
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}
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