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#ifndef LUMINANCE_GLSLLIB
#define LUMINANCE_GLSLLIB

// Luma coefficients according to ITU-R Recommendation BT.709 (http://en.wikipedia.org/wiki/Rec._709)
const vec3 yCoeff_709 = vec3( 0.2126, 0.7152, 0.0722 );

float luminance( in vec3 v )
{
  return dot( v, yCoeff_709 );
}

vec3 RGBToYPbPr( in vec3 v )
{
    vec3 ypp;
    ypp.x = luminance( v );
    ypp.y = 0.5 * (v.b - ypp.x) / (1.0 - yCoeff_709.b);
    ypp.z = 0.5 * (v.r - ypp.x) / (1.0 - yCoeff_709.r);

    return ypp;
}

vec3 YPbPrToRGB( in vec3 v )
{
    vec3 outRGB;
    outRGB.x = dot(vec3(1.0, 0.0, 1.575), v);
    outRGB.y = dot(vec3(1.0, -0.187, -0.468), v);
    outRGB.z = dot(vec3(1.0, 1.856, 0.0), v);

    return outRGB;
}

#endif