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const float LIM_CYAN    = 1.147;
const float LIM_MAGENTA = 1.264;
const float LIM_YELLOW  = 1.312;

// Percentage of the core gamut to protect
// Values calculated to protect all the colors of the ColorChecker Classic 24 as given by
// ISO 17321-1 and Ohta (1997)
const float THR_CYAN    = 0.815;
const float THR_MAGENTA = 0.803;
const float THR_YELLOW  = 0.880;

// Aggressiveness of the compression curve
const float PWR = 1.2;

// Calculate compressed distance
float compress(float dist, float lim, float thr, float pwr) {
    float compressedDist, scl, nd, p;

    if (dist < thr) {
        compressedDist = dist; // No compression below threshold
    } else {
        // Calculate scale factor for y = 1 intersect
        scl = (lim - thr) / pow(pow((1.0 - thr) / (lim - thr), -pwr) - 1.0, 1.0 / pwr);

        // Normalize distance outside threshold by scale factor
        nd = (dist - thr) / scl;
        p = pow(nd, pwr);

        compressedDist = thr + scl * nd / (pow(1.0 + p, 1.0 / pwr)); // Compress
    }
    return compressedDist;
}

void compressionLMT(inout vec3 color) {
    // Achromatic axis
    float achromaticAxis = maxOf(color);

    // Distance from the achromatic axis for each color component aka inverse RGB ratios
    vec3 dist = achromaticAxis == 0.0 ? vec3(0.0) : (achromaticAxis - color) / abs(achromaticAxis);

    // Compress distance with parameterized shaper function
    vec3 compressedDist;
    compressedDist.r = compress(dist.r, LIM_CYAN   , THR_CYAN   , PWR);
    compressedDist.g = compress(dist.g, LIM_MAGENTA, THR_MAGENTA, PWR);
    compressedDist.b = compress(dist.b, LIM_YELLOW , THR_YELLOW , PWR);

    // Recalculate RGB from compressed distance and achromatic
    color = achromaticAxis - compressedDist * abs(achromaticAxis);
}
