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| /**
| * Converts an RGB color to HSB (hue, saturation, brightness)
| * HSB <-> RGB conversion with minimal branching: {@link http://lolengine.net/blog/2013/07/27/rgb-to-hsv-in-glsl}
| *
| * @name czm_RGBToHSB
| * @glslFunction
| *
| * @param {vec3} rgb The color in RGB.
| *
| * @returns {vec3} The color in HSB.
| *
| * @example
| * vec3 hsb = czm_RGBToHSB(rgb);
| * hsb.z *= 0.1;
| * rgb = czm_HSBToRGB(hsb);
| */
|
| const vec4 K_RGB2HSB = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
|
| vec3 czm_RGBToHSB(vec3 rgb)
| {
| vec4 p = mix(vec4(rgb.bg, K_RGB2HSB.wz), vec4(rgb.gb, K_RGB2HSB.xy), step(rgb.b, rgb.g));
| vec4 q = mix(vec4(p.xyw, rgb.r), vec4(rgb.r, p.yzx), step(p.x, rgb.r));
|
| float d = q.x - min(q.w, q.y);
| return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + czm_epsilon7)), d / (q.x + czm_epsilon7), q.x);
| }
|
|
