canvasutil
Version:
Pixel transformations and processing for canvas
203 lines (178 loc) • 5.32 kB
JavaScript
/**
* copyright 2011 Ryan Day
* http://github.com/soldair/node-canvasutil
*
* Licensed under the MIT license:
* http://www.opensource.org/licenses/mit-license.php
*
* rgbToHsl,rgbToHsl,rgbToHsv,hsvToRgb functions were ported to js by:
*
* http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
* Copyright © 2008—2010 Michael Jackson.
*/
var conversionlib = module.exports = {
rgbToHsl:rgbToHsl,
hslToRgb:hslToRgb,
rgbToHsv:rgbToHsv,
hsvToRgb:hsvToRgb,
rgbToYuv:rgbToYuv,
yuvToRgb:yuvToRgb,
luma709Only:luma709Only
};
/**
* Converts an RGB color value to HSL. Conversion formula
* adapted from http://en.wikipedia.org/wiki/HSL_color_space.
* Assumes r, g, and b are contained in the set [0, 255] and
* returns h, s, and l in the set [0, 1].
*
* @param Number r The red color value
* @param Number g The green color value
* @param Number b The blue color value
* @return Array The HSL representation
*/
function rgbToHsl(r, g, b){
r /= 255, g /= 255, b /= 255;
var max = Math.max(r, g, b), min = Math.min(r, g, b);
var h, s, l = (max + min) / 2;
if(max == min){
h = s = 0; // achromatic
}else{
var d = max - min;
s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
switch(max){
case r: h = (g - b) / d + (g < b ? 6 : 0); break;
case g: h = (b - r) / d + 2; break;
case b: h = (r - g) / d + 4; break;
}
h /= 6;
}
return [h, s, l];
}
/**
* Converts an HSL color value to RGB. Conversion formula
* adapted from http://en.wikipedia.org/wiki/HSL_color_space.
* Assumes h, s, and l are contained in the set [0, 1] and
* returns r, g, and b in the set [0, 255].
*
* @param Number h The hue
* @param Number s The saturation
* @param Number l The lightness
* @return Array The RGB representation
*/
function hslToRgb(h, s, l){
var r, g, b;
if(s == 0){
r = g = b = l; // achromatic
}else{
function hue2rgb(p, q, t){
if(t < 0) t += 1;
if(t > 1) t -= 1;
if(t < 1/6) return p + (q - p) * 6 * t;
if(t < 1/2) return q;
if(t < 2/3) return p + (q - p) * (2/3 - t) * 6;
return p;
}
var q = l < 0.5 ? l * (1 + s) : l + s - l * s;
var p = 2 * l - q;
r = hue2rgb(p, q, h + 1/3);
g = hue2rgb(p, q, h);
b = hue2rgb(p, q, h - 1/3);
}
return [r * 255, g * 255, b * 255];
}
/**
* Converts an RGB color value to HSV. Conversion formula
* adapted from http://en.wikipedia.org/wiki/HSV_color_space.
* Assumes r, g, and b are contained in the set [0, 255] and
* returns h, s, and v in the set [0, 1].
*
* @param Number r The red color value
* @param Number g The green color value
* @param Number b The blue color value
* @return Array The HSV representation
*/
function rgbToHsv(r, g, b){
r = r/255, g = g/255, b = b/255;
var max = Math.max(r, g, b), min = Math.min(r, g, b);
var h, s, v = max;
var d = max - min;
s = max == 0 ? 0 : d / max;
if(max == min){
h = 0; // achromatic
}else{
switch(max){
case r: h = (g - b) / d + (g < b ? 6 : 0); break;
case g: h = (b - r) / d + 2; break;
case b: h = (r - g) / d + 4; break;
}
h /= 6;
}
return [h, s, v];
}
/**
* Converts an HSV color value to RGB. Conversion formula
* adapted from http://en.wikipedia.org/wiki/HSV_color_space.
* Assumes h, s, and v are contained in the set [0, 1] and
* returns r, g, and b in the set [0, 255].
*
* @param Number h The hue
* @param Number s The saturation
* @param Number v The value
* @return Array The RGB representation
*/
function hsvToRgb(h, s, v){
var r, g, b;
var i = Math.floor(h * 6);
var f = h * 6 - i;
var p = v * (1 - s);
var q = v * (1 - f * s);
var t = v * (1 - (1 - f) * s);
switch(i % 6){
case 0: r = v, g = t, b = p; break;
case 1: r = q, g = v, b = p; break;
case 2: r = p, g = v, b = t; break;
case 3: r = p, g = q, b = v; break;
case 4: r = t, g = p, b = v; break;
case 5: r = v, g = p, b = q; break;
}
return [r * 255, g * 255, b * 255];
}
//NOTE YUV is a lossy conversion
function rgbToYuv(r,g,b){
var Wr = 0.2126
,Wb = 0.0722
,Wg = 1-Wr-Wb
,Umax = 0.436
,Vmax = 0.615;
var y = Wr*r+Wg*g+Wb*b
,u = Umax*((b-y)/(1-Wb))
,v = Vmax*((r-y)/(1-Wr));
return [y,u,v];
}
//NOTE YUV is a lossy conversion. its useful though so dont write it off yet ;)
function yuvToRgb(r,g,b){
var Wr = 0.2126
,Wb = 0.0722
,Wg = 0.7152//1-Wr-Wb
,Umax = 0.436
,Vmax = 0.615;
var y = Wr*r+Wg*g+Wb*b
,u = Umax*((b-y)/(1-Wb))
,v = Vmax*((r-y)/(1-Wr));
return [y,u,v];
}
function yuvToRgb(y,u,v){
var Wr = 0.2126
,Wb = 0.0722
,Wg = 0.7152//1-Wr-Wb
,Umax = 0.436
,Vmax = 0.615;
//TODO pre calculate known values
var r = y+(v*(1-Wr/Vmax))
,g = y-(u*(Wb*(1-Wb)/(Umax-Wg)))-(v*(Wr*(1-Wr)/Vmax*Wg))
,b = y+(u*((1-Wb)/Umax));
return [r,g,b];
}
function luma709Only(r,g,b){
return (0.2125*r + 0.7154*g + 0.0721*b)
}