three.js/examples/js/shaders/HueSaturationShader.js

( function () {

	/**
 * Hue and saturation adjustment
 * https://github.com/evanw/glfx.js
 * hue: -1 to 1 (-1 is 180 degrees in the negative direction, 0 is no change, etc.
 * saturation: -1 to 1 (-1 is solid gray, 0 is no change, and 1 is maximum contrast)
 */
	var HueSaturationShader = {
		uniforms: {
			'tDiffuse': {
				value: null
			},
			'hue': {
				value: 0
			},
			'saturation': {
				value: 0
			}
		},
		vertexShader: [ 'varying vec2 vUv;', 'void main() {', '	vUv = uv;', '	gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );', '}' ].join( '\n' ),
		fragmentShader: [ 'uniform sampler2D tDiffuse;', 'uniform float hue;', 'uniform float saturation;', 'varying vec2 vUv;', 'void main() {', '	gl_FragColor = texture2D( tDiffuse, vUv );', // hue
			'	float angle = hue * 3.14159265;', '	float s = sin(angle), c = cos(angle);', '	vec3 weights = (vec3(2.0 * c, -sqrt(3.0) * s - c, sqrt(3.0) * s - c) + 1.0) / 3.0;', '	float len = length(gl_FragColor.rgb);', '	gl_FragColor.rgb = vec3(', '		dot(gl_FragColor.rgb, weights.xyz),', '		dot(gl_FragColor.rgb, weights.zxy),', '		dot(gl_FragColor.rgb, weights.yzx)', '	);', // saturation
			'	float average = (gl_FragColor.r + gl_FragColor.g + gl_FragColor.b) / 3.0;', '	if (saturation > 0.0) {', '		gl_FragColor.rgb += (average - gl_FragColor.rgb) * (1.0 - 1.0 / (1.001 - saturation));', '	} else {', '		gl_FragColor.rgb += (average - gl_FragColor.rgb) * (-saturation);', '	}', '}' ].join( '\n' )
	};

	THREE.HueSaturationShader = HueSaturationShader;

} )();