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

console.warn( "THREE.SepiaShader: As part of the transition to ES6 Modules, the files in 'examples/js' were deprecated in May 2020 (r117) and will be deleted in December 2020 (r124). You can find more information about developing using ES6 Modules in https://threejs.org/docs/index.html#manual/en/introduction/Import-via-modules." );
/**
 * @author alteredq / http://alteredqualia.com/
 *
 * Sepia tone shader
 * based on glfx.js sepia shader
 * https://github.com/evanw/glfx.js
 */

THREE.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" )

};