srgb-transform.ts

/* 
 * sRGB transform (TypeScript)
 * 
 * Copyright (c) 2020 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.
 */


namespace srgbtransform {
	
	export function srgbToLinear(x: number): number {
		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);
	}
	
	
	export function srgb8BitToLinear(x: number): number {
		if ((x | 0) != x || (x >>> 8) != 0)
			throw "Value out of 8-bit range";
		return SRGB_8BIT_TO_LINEAR[x];
	}
	
	
	export function linearToSrgb(x: number): number {
		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;
	}
	
	
	export function linearToSrgb8Bit(x: number): number {
		if (x <= 0)
			return 0;
		const TABLE: Array<number> = SRGB_8BIT_TO_LINEAR;
		if (x >= 1)
			return TABLE.length - 1;
		let y: number = 0;
		for (let 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;
	}
	
	
	let SRGB_8BIT_TO_LINEAR: Array<number> = [];
	for (let i = 0; i < 256; i++)
		SRGB_8BIT_TO_LINEAR.push(srgbToLinear(i / 255.0));
	
}