srgb-transform.js

/* 
 * sRGB transform (JavaScript)
 * 
 * Copyright (c) 2017 Project Nayuki. (MIT License)
 * https://www.nayuki.io/page/srgb-transform-library
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 * - The above copyright notice and this permission notice shall be included in
 *   all copies or substantial portions of the Software.
 * - The Software is provided "as is", without warranty of any kind, express or
 *   implied, including but not limited to the warranties of merchantability,
 *   fitness for a particular purpose and noninfringement. In no event shall the
 *   authors or copyright holders be liable for any claim, damages or other
 *   liability, whether in an action of contract, tort or otherwise, arising from,
 *   out of or in connection with the Software or the use or other dealings in the
 *   Software.
 */

"use strict";


var srgbtransform = new function() {
	
	this.srgbToLinear = function(x) {
		if (x <= 0)
			return 0;
		else if (x >= 1)
			return 1;
		else if (x < 0.04045)
			return x / 12.92;
		else
			return Math.pow((x + 0.055) / 1.055, 2.4);
	};
	
	
	this.srgb8BitToLinear = function(x) {
		if ((x | 0) != x || (x >>> 8) != 0)
			throw "Value out of 8-bit range";
		return SRGB_8BIT_TO_LINEAR[x];
	};
	
	
	this.linearToSrgb = function(x) {
		if (x <= 0)
			return 0;
		else if (x >= 1)
			return 1;
		else if (x < 0.0031308)
			return x * 12.92;
		else
			return Math.pow(x, 1 / 2.4) * 1.055 - 0.055;
	};
	
	
	this.linearToSrgb8Bit = function(x) {
		if (x <= 0)
			return 0;
		var TABLE = SRGB_8BIT_TO_LINEAR;
		if (x >= 1)
			return TABLE.length - 1;
		var y = 0;
		for (var i = TABLE.length >>> 1; i != 0; i >>>= 1) {
			if (TABLE[y | i] <= x)
				y |= i;
		}
		if (x - TABLE[y] <= TABLE[y + 1] - x)
			return y;
		else
			return y + 1;
	};
	
	
	var SRGB_8BIT_TO_LINEAR = [];
	for (var i = 0; i < 256; i++)
		SRGB_8BIT_TO_LINEAR.push(this.srgbToLinear(i / 255.0));
	
};