#version 150

// https://gist.github.com/mairod/a75e7b44f68110e1576d77419d608786

vec3 hueShift( vec3 color, float hueAdjust ) {
    const vec3  kRGBToYPrime = vec3 (0.299, 0.587, 0.114);
    const vec3  kRGBToI      = vec3 (0.596, -0.275, -0.321);
    const vec3  kRGBToQ      = vec3 (0.212, -0.523, 0.311);

    const vec3  kYIQToR     = vec3 (1.0, 0.956, 0.621);
    const vec3  kYIQToG     = vec3 (1.0, -0.272, -0.647);
    const vec3  kYIQToB     = vec3 (1.0, -1.107, 1.704);

    float   YPrime  = dot (color, kRGBToYPrime);
    float   I       = dot (color, kRGBToI);
    float   Q       = dot (color, kRGBToQ);
    float   hue     = atan (Q, I);
    float   chroma  = sqrt (I * I + Q * Q);

    hue += hueAdjust;

    Q = chroma * sin (hue);
    I = chroma * cos (hue);

    vec3 yIQ = vec3 (YPrime, I, Q);

    return vec3( dot (yIQ, kYIQToR), dot (yIQ, kYIQToG), dot (yIQ, kYIQToB) );
}