three.js/examples/js/shaders/ToneMapShader.js

/**
 * Full-screen tone-mapping shader based on http://www.cis.rit.edu/people/faculty/ferwerda/publications/sig02_paper.pdf
 */

THREE.ToneMapShader = {

	uniforms: {

		'tDiffuse': { value: null },
		'averageLuminance': { value: 1.0 },
		'luminanceMap': { value: null },
		'maxLuminance': { value: 16.0 },
		'minLuminance': { value: 0.01 },
		'middleGrey': { value: 0.6 }
	},

	vertexShader: [

		'varying vec2 vUv;',

		'void main() {',

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

		'}'

	].join( '\n' ),

	fragmentShader: [

		'#include <common>',

		'uniform sampler2D tDiffuse;',

		'varying vec2 vUv;',

		'uniform float middleGrey;',
		'uniform float minLuminance;',
		'uniform float maxLuminance;',
		'#ifdef ADAPTED_LUMINANCE',
		'	uniform sampler2D luminanceMap;',
		'#else',
		'	uniform float averageLuminance;',
		'#endif',

		'vec3 ToneMap( vec3 vColor ) {',
		'	#ifdef ADAPTED_LUMINANCE',
		// Get the calculated average luminance
		'		float fLumAvg = texture2D(luminanceMap, vec2(0.5, 0.5)).r;',
		'	#else',
		'		float fLumAvg = averageLuminance;',
		'	#endif',

		// Calculate the luminance of the current pixel
		'	float fLumPixel = linearToRelativeLuminance( vColor );',

		// Apply the modified operator (Eq. 4)
		'	float fLumScaled = (fLumPixel * middleGrey) / max( minLuminance, fLumAvg );',

		'	float fLumCompressed = (fLumScaled * (1.0 + (fLumScaled / (maxLuminance * maxLuminance)))) / (1.0 + fLumScaled);',
		'	return fLumCompressed * vColor;',
		'}',

		'void main() {',

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

		'	gl_FragColor = vec4( ToneMap( texel.xyz ), texel.w );',

		'}'

	].join( '\n' )

};