LYGIA Shader Library

Dependencies:

• lygia/color/space/rgb2hcv.glsl
• lygia/color/space/hue2rgb.glsl

Use:

<vec3|vec4> rgb2hcy(<vec3|vec4> rgb)

Check it on Github

#ifndef HCY_EPSILON
#define HCY_EPSILON 1e-10
#endif

#ifndef FNC_RGB2HCY
#define FNC_RGB2HCY
vec3 rgb2hcy(const in vec3 rgb) {
    const vec3 HCYwts = vec3(0.299, 0.587, 0.114);
    // Corrected by David Schaeffer
    vec3 HCV = rgb2hcv(rgb);
    float Y = dot(rgb, HCYwts);
    float Z = dot(hue2rgb(HCV.x), HCYwts);
    if (Y < Z) {
        HCV.y *= Z / (HCY_EPSILON + Y);
    } else {
        HCV.y *= (1.0 - Z) / (HCY_EPSILON + 1.0 - Y);
    }
    return vec3(HCV.x, HCV.y, Y);
}
vec4 rgb2hcy(vec4 rgb) { return vec4(rgb2hcy(rgb.rgb), rgb.a);}
#endif

Dependencies:

• lygia/color/space/rgb2hcv.glsl
• lygia/color/space/hue2rgb.glsl

Use:

<float3|float4> rgb2hcy(<float3|float4> rgb)

Check it on Github

#ifndef HCY_EPSILON
#define HCY_EPSILON 1e-10
#endif

#ifndef FNC_RGB2HCY
#define FNC_RGB2HCY
float3 rgb2hcy(float3 rgb) {
    const float3 HCYwts = float3(0.299, 0.587, 0.114);
    // Corrected by David Schaeffer
    float3 HCV = rgb2hcv(rgb);
    float Y = dot(rgb, HCYwts);
    float Z = dot(hue2rgb(HCV.x), HCYwts);
    if (Y < Z) {
        HCV.y *= Z / (HCY_EPSILON + Y);
    } else {
        HCV.y *= (1.0 - Z) / (HCY_EPSILON + 1.0 - Y);
    }
    return float3(HCV.x, HCV.y, Y);
}
float4 rgb2hcy(float4 rgb) { return float4(rgb2hcy(rgb.rgb), rgb.a);}
#endif

Dependencies:

• lygia/color/space/rgb2hcv.glsl
• lygia/color/space/hue2rgb.glsl

Check it on Github

fn rgb2hcy(rgb: vec3f) -> vec3f {
    let HCYwts = vec3f(0.299, 0.587, 0.114);
    // Corrected by David Schaeffer
    var HCV = rgb2hcv(rgb);
    let Y = dot(rgb, HCYwts);
    let Z = dot(hue2rgb(HCV.x), HCYwts);
    if (Y < Z) {
        HCV.y *= Z / (HCY_EPSILON + Y);
    } else {
        HCV.y *= (1.0 - Z) / (HCY_EPSILON + 1.0 - Y);
    }
    return vec3f(HCV.x, HCV.y, Y);
}