/*************************************************************************/
/*                  License Terms for ACES Components                    */
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/*  ACES software and tools are provided by the Academy under the        */
/*  following terms and conditions: A worldwide, royalty-free,           */
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/*  Copyright © 2014 Academy of Motion Picture Arts and Sciences         */
/*  (A.M.P.A.S.). Portions contributed by others as indicated.           */
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/*************************************************************************/

float YTolinearCV(float y, float maxY, float minY) {
    return (y - minY) / (maxY - minY);
}

vec3 darkSurroundToDimSurround(vec3 linearCV) {
    vec3 xyY = xyzToXyV(linearCV * AP1_2_XYZ_MAT);
    xyY.b    = pow(saturate(xyY.b), DIM_SURROUND_GAMMA);
    return xyYToXYZ(xyY) * XYZ_2_AP1_MAT;
}

// Gamma curves

float moncurve_r(float y, float gamma, float offset) {
    float yb = pow(offset * gamma / (( gamma - 1.0) * (1.0 + offset)), gamma);
    float rs = pow((gamma - 1.0) / offset, gamma - 1.0) * pow((1.0 + offset) / gamma, gamma);

    if (y >= yb) return (1.0 + offset) * pow(y, 1.0 / gamma) - offset;
    else        return y * rs;
}

float bt1886_r(float L, float gamma, float Lw, float Lb) {
    float a = pow(pow(Lw, 1.0 / gamma) - pow(Lb, 1.0 / gamma), gamma);
    float b = pow(Lb, 1.0 / gamma) / (pow(Lw, 1.0 / gamma) - pow(Lb, 1.0 / gamma));
    float V = pow(max(L / a, 0.0), 1.0 / gamma) - b;
    return V;
}

void odt(inout vec3 color) {
    // Apply the tonescale independently in rendering-space RGB
    color.r = segmentedSplineC9Fwd(color.r);
    color.g = segmentedSplineC9Fwd(color.g);
    color.b = segmentedSplineC9Fwd(color.b);

    // Scale luminance to linear code value
    color.r = YTolinearCV(color.r, ODT_CINEMA_WHITE, ODT_CINEMA_BLACK);
    color.g = YTolinearCV(color.g, ODT_CINEMA_WHITE, ODT_CINEMA_BLACK);
    color.b = YTolinearCV(color.b, ODT_CINEMA_WHITE, ODT_CINEMA_BLACK);

    color  = darkSurroundToDimSurround(color);               // Apply gamma adjustment to compensate for dim surround
    color *= calcSatAdjustMatrix(ODT_SAT_FACTOR, AP1_RGB2Y); // Apply desaturation to compensate for luminance difference

    color *= AP1_2_XYZ_MAT; // Rendering space RGB to XYZ
    color *= D60_2_D65_CAT; // Apply CAT from ACES white point to assumed observer adapted white point

    // CIE XYZ to display primaries and handling out-of-gamut values
    color = saturate(color * XYZ_2_SRGB_MAT);

    // Gamma curve to convert back to monitor RGB
    color.r = bt1886_r(color.r, ODT_DISPGAMMA, 1.0, 0.0);
    color.g = bt1886_r(color.g, ODT_DISPGAMMA, 1.0, 0.0);
    color.b = bt1886_r(color.b, ODT_DISPGAMMA, 1.0, 0.0);
}