three.js/examples/jsm/shaders/SepiaShader.js

/**
 * Sepia tone shader
 * based on glfx.js sepia shader
 * https://github.com/evanw/glfx.js
 */

var SepiaShader = {

	uniforms: {

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

	},

	vertexShader: [

		'varying vec2 vUv;',

		'void main() {',

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

		'}'

	].join( '\n' ),

	fragmentShader: [

		'uniform float amount;',

		'uniform sampler2D tDiffuse;',

		'varying vec2 vUv;',

		'void main() {',

		'	vec4 color = texture2D( tDiffuse, vUv );',
		'	vec3 c = color.rgb;',

		'	color.r = dot( c, vec3( 1.0 - 0.607 * amount, 0.769 * amount, 0.189 * amount ) );',
		'	color.g = dot( c, vec3( 0.349 * amount, 1.0 - 0.314 * amount, 0.168 * amount ) );',
		'	color.b = dot( c, vec3( 0.272 * amount, 0.534 * amount, 1.0 - 0.869 * amount ) );',

		'	gl_FragColor = vec4( min( vec3( 1.0 ), color.rgb ), color.a );',

		'}'

	].join( '\n' )

};

export { SepiaShader };