three.js/examples/js/shaders/BleachBypassShader.js

/**
 * Bleach bypass shader [http://en.wikipedia.org/wiki/Bleach_bypass]
 * - based on Nvidia example
 * http://developer.download.nvidia.com/shaderlibrary/webpages/shader_library.html#post_bleach_bypass
 */

THREE.BleachBypassShader = {

	uniforms: {

		'tDiffuse': { value: null },
		'opacity': { value: 1.0 }

	},

	vertexShader: [

		'varying vec2 vUv;',

		'void main() {',

		'	vUv = uv;',
		'	gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );',

		'}'

	].join( '\n' ),

	fragmentShader: [

		'uniform float opacity;',

		'uniform sampler2D tDiffuse;',

		'varying vec2 vUv;',

		'void main() {',

		'	vec4 base = texture2D( tDiffuse, vUv );',

		'	vec3 lumCoeff = vec3( 0.25, 0.65, 0.1 );',
		'	float lum = dot( lumCoeff, base.rgb );',
		'	vec3 blend = vec3( lum );',

		'	float L = min( 1.0, max( 0.0, 10.0 * ( lum - 0.45 ) ) );',

		'	vec3 result1 = 2.0 * base.rgb * blend;',
		'	vec3 result2 = 1.0 - 2.0 * ( 1.0 - blend ) * ( 1.0 - base.rgb );',

		'	vec3 newColor = mix( result1, result2, L );',

		'	float A2 = opacity * base.a;',
		'	vec3 mixRGB = A2 * newColor.rgb;',
		'	mixRGB += ( ( 1.0 - A2 ) * base.rgb );',

		'	gl_FragColor = vec4( mixRGB, base.a );',

		'}'

	].join( '\n' )

};