three.js/examples/js/shaders/TechnicolorShader.js

console.warn( "THREE.TechnicolorShader: 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 flimshaw / http://charliehoey.com
 *
 * Technicolor Shader
 * Simulates the look of the two-strip technicolor process popular in early 20th century films.
 * More historical info here: http://www.widescreenmuseum.com/oldcolor/technicolor1.htm
 * Demo here: http://charliehoey.com/technicolor_shader/shader_test.html
 */

THREE.TechnicolorShader = {

	uniforms: {

		"tDiffuse": { value: null }

	},

	vertexShader: [

		"varying vec2 vUv;",

		"void main() {",

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

		"}"

	].join( "\n" ),

	fragmentShader: [

		"uniform sampler2D tDiffuse;",
		"varying vec2 vUv;",

		"void main() {",

		"	vec4 tex = texture2D( tDiffuse, vec2( vUv.x, vUv.y ) );",
		"	vec4 newTex = vec4(tex.r, (tex.g + tex.b) * .5, (tex.g + tex.b) * .5, 1.0);",

		"	gl_FragColor = newTex;",

		"}"

	].join( "\n" )

};