/**
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* Adjusts the saturation of a color.
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*
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* @name czm_saturation
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* @glslFunction
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*
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* @param {vec3} rgb The color.
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* @param {float} adjustment The amount to adjust the saturation of the color.
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*
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* @returns {float} The color with the saturation adjusted.
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*
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* @example
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* vec3 greyScale = czm_saturation(color, 0.0);
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* vec3 doubleSaturation = czm_saturation(color, 2.0);
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*/
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vec3 czm_saturation(vec3 rgb, float adjustment)
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{
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// Algorithm from Chapter 16 of OpenGL Shading Language
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const vec3 W = vec3(0.2125, 0.7154, 0.0721);
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vec3 intensity = vec3(dot(rgb, W));
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return mix(intensity, rgb, adjustment);
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}
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