/*-

 * sRGB.h

 *

 * Last changed in libpng 1.6.0 [February 14, 2013]

 *

 * COPYRIGHT: Written by John Cunningham Bowler, 2013.

 * To the extent possible under law, the author has waived all copyright and

 * related or neighboring rights to this work.  This work is published from:

 * United States.

 *

 * Utility file; not actually a header, this contains definitions of sRGB

 * calculation functions for inclusion in those test programs that need them.

 *

 * All routines take and return a floating point value in the range

 * 0 to 1.0, doing a calculation according to the sRGB specification

 * (in fact the source of the numbers is the wikipedia article at

 * http://en.wikipedia.org/wiki/SRGB).

 */

static double

sRGB_from_linear(double l)

{

   if (l <= 0.0031308)

      l *= 12.92;

   else

      l = 1.055 * pow(l, 1/2.4) - 0.055;

   return l;

}

static double

linear_from_sRGB(double s)

{

   if (s <= 0.04045)

      return s / 12.92;

   else

      return pow((s+0.055)/1.055, 2.4);

}

static double

YfromRGB(double r, double g, double b)

{

   /* Use the sRGB (rounded) coefficients for Rlinear, Glinear, Blinear to get

    * the CIE Y value (also linear).

    */

   return 0.2126 * r + 0.7152 * g + 0.0722 * b;

}