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Canvas change image background color but keep it's "effects"

I have an image where I need to change it's background color, but keep the "effects" on it (on the image the black dots, white lines etc.)
Here's the orginal image:
I managed to change the color, but also I keep removing those "effects". Preview:
Here's the code:
//let's say I want it to be red
var r = 255;
var g = 0;
var b = 0;
var imgElement = document.getElementById('img');
var canvas = document.getElementById('canvas');
canvas.width = imgElement.width;
canvas.height = imgElement.height;
var ctx = canvas.getContext("2d");
ctx.drawImage(imgElement, 0, 0);
var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
var data = imageData.data;
for (var i = 0; i < data.length; i += 4) {
if (data[i + 3] !== 0) {
data[i] = r;
data[i + 1] = g;
data[i + 2] = b;
data[i + 3] = data[i + 3];
}
}
ctx.putImageData(imageData, 0, 0);
<img src="foo" id="img" />
<canvas id="canvas"></canvas>
How to prevent that?

For modern browsers except Internet Explorer, you can use compositing to change the hue of your original image while leaving the saturation & lightness unchanged. This will "recolor" your original image while leaving the contours intact.
Example code that works in modern browsers except Internet Explorer
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var img=new Image();
img.onload=start;
img.src="https://dl.dropboxusercontent.com/u/139992952/multple/M449a.png";
function start(){
// create an overlay with solid #00d9c6 color
var tempCanvas=document.createElement('canvas');
var tempctx=tempCanvas.getContext('2d');
canvas.width=tempCanvas.width=img.width;
canvas.height=tempCanvas.height=img.height;
tempctx.drawImage(img,0,0);
tempctx.globalCompositeOperation='source-atop';
tempctx.fillStyle='#00d9c6';
tempctx.fillRect(0,0,tempCanvas.width,tempCanvas.height);
//
canvas.width=img.width;
canvas.height=img.height;
// use compositing to change the hue of the original image
ctx.drawImage(img,0,0);
ctx.globalCompositeOperation='hue';
ctx.drawImage(tempCanvas,0,0);
// always clean up: reset compositing to its default
ctx.globalCompositeOperation='source-over';
}
#canvas{border:1px solid red; }
<canvas id="canvas" width=300 height=300></canvas>
Since Internet Explorer does not support Blend Compositing, you will have to do it manually.
Read the RGBA value of each pixel.
Convert that RGBA value to HSL.
Shift the hue value (the "H" in HSL) by the difference between your blue hue and your desired green hue.
Convert the hue-shifted HSL value to RGBA value.
Write the hue-shifted RGBA value back to the pixel.
Here's example code of manually shifting the hue:
Important note: This manual method works by manipulating pixels with .getImageData. Therefore you must make sure the original image is hosted on the same domain as the webpage. Otherwise, the canvas will become tainted for security reasons and you will not be able to use .getImageData.
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var img = new Image();
img.crossOrigin = "anonymous";
img.onload = start;
img.src = "https://dl.dropboxusercontent.com/u/139992952/multple/marioStanding.png";
function start() {
ctx.drawImage(img, 0, 0);
ctx.drawImage(img, 150, 0);
// shift blueish colors to greenish colors
recolorPants(-.33);
}
function recolorPants(colorshift) {
var imgData = ctx.getImageData(150, 0, canvas.width, canvas.height);
var data = imgData.data;
for (var i = 0; i < data.length; i += 4) {
red = data[i + 0];
green = data[i + 1];
blue = data[i + 2];
alpha = data[i + 3];
// skip transparent/semiTransparent pixels
if (alpha < 200) {
continue;
}
var hsl = rgbToHsl(red, green, blue);
var hue = hsl.h * 360;
// change blueish pixels to the new color
if (hue > 200 && hue < 300) {
var newRgb = hslToRgb(hsl.h + colorshift, hsl.s, hsl.l);
data[i + 0] = newRgb.r;
data[i + 1] = newRgb.g;
data[i + 2] = newRgb.b;
data[i + 3] = 255;
}
}
ctx.putImageData(imgData, 150, 0);
}
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: h,
s: s,
l: l,
});
}
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: Math.round(r * 255),
g: Math.round(g * 255),
b: Math.round(b * 255),
});
}
<p>Example shifting color Hue with .getImageData</p>
<p>(Original: left, Recolored: right)</p>
<canvas id="canvas" width=300 height=300></canvas>

You need to convert each pixel to the LSH colour space (lightness/luminance, hue, saturation). Then you set the Hue to the colour you want and keep the calculated luminance and saturation, then convert back to RGB and set the imageData to the new RGB value.
I have added my own code for conversions. There may be faster versions out there.
// returns RGB in an array on 3 numbers 0-255
var lshToRGB = function(ll,ss,hh){ //ll 0-255,ss 0-255, hh 0-360
var l = ll/255;
var s = ss/255;
var hhh = (hh/255)*360;
var C = (1 - Math.abs(2*l - 1)) * s;
var X = C*(1 - Math.abs(((hhh / 60)%2) - 1));
var m = l - C/2;
if(hhh < 60){
var r = C;
var g = X;
var b = 0;
}else
if(hhh < 120){
var r = X;
var g = C;
var b = 0;
}else
if(hhh < 180){
var r = 0;
var g = C;
var b = X;
}else
if(hhh < 240){
var r = 0;
var g = X;
var b = C;
}else
if(hhh < 300){
var r = X;
var g = 0;
var b = C;
}else{
var r = C;
var g = 0;
var b = X;
}
r += m;
g += m;
b += m;
// is there a need to clamp these ????)
r = Math.round(Math.min(255,Math.max(0,r*255)));
g = Math.round(Math.min(255,Math.max(0,g*255)));
b = Math.round(Math.min(255,Math.max(0,b*255)));
return [r,g,b];
}
// returns array of 3 numbers 0-255,0-255,0-360
var rgbToLSH = function(rr,gg,bb){ // could do without the conversion from 360 to 255 on hue
var r,
g,
b,
h,
s,
l,
min,
max,
d;
r = rr / 255;
g = gg / 255;
b = bb / 255;
max = Math.max(r, g, b);
min = Math.min(r, g, b);
l = (max + min) / 2;
if (max == min) {
h = 0;
s = 0; // achromatic
} else {
d = max - min;
s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
switch (max) {
case r:
h = (g - b) / d;
break;
case g:
h = 2 + ((b - r) / d);
break;
case b:
h = 4 + ((r - g) / d);
break;
}
h *= 60;
if (h < 0) {
h += 360;
}
h = Math.round(h);
}
return [
Math.min(Math.round(l*255),255),
Math.min(Math.round(s*255),255),
Math.min(Math.round((h/360)*255),255)
];
}

HTML5 Canvas image segmentation

I'm trying to remove the white/gray pixels of background (a wall) from an image so that the foreground (a hand in my case) should be left.
I tried manipulating canvas pixels but the foreground extraction is not very nice because of shadow or other inconsistencies in background. I even tried with green colored background but it doesn't enhance the performance.
for (i = 0; i < imgData.width * imgData.height * 4; i += 4) {
var r = imgDataNormal.data[i + 0];
var g = imgDataNormal.data[i + 1];
var b = imgDataNormal.data[i + 2];
var a = imgDataNormal.data[i + 3];
// compare rgb levels for green and set alphachannel to 0;
selectedR = *a value 0 - 255*
selectedG = *a value 0 - 255*
selectedB = *a value 0 - 255*
if (r <= selectedR || g >= selectedG || b <= selectedB) {
a = 0;
}
}
Is there any sophisticated method or library to make background of an image transparent?

Converting the pixels from RGB to HSL and then running a threshold filter over the pixels to remove anything (by setting the pixel's alpha to be completely transparent) with a saturation less than 0.12 (measuring saturation on a scale of 0..1 - that value was found via trial-and-error).
JavaScript
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];
}
function thresholdHsl(pixels,lower,upper){
var d = pixels.data;
var createTest = function( lower, upper ){
return lower <= upper
? function(v){ return lower <= v && v <= upper; }
: function(v){ return lower <= v || v <= upper; };
}
var h = createTest( lower[0], upper[0] );
var s = createTest( lower[1], upper[1] );
var l = createTest( lower[2], upper[2] );
for (var i=0; i<d.length; i+=4) {
var hsl = rgbToHsl( d[i], d[i+1], d[i+2] );
if ( !h(hsl[0]) || !s(hsl[1]) || !l(hsl[2]) ){
d[i+3] = 0;
}
}
}
var img = new Image();
img.onload = function() {
var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext('2d');
ctx.drawImage(img,0,0);
var pixels = ctx.getImageData(0,0,canvas.width,canvas.height);
thresholdHsl(pixels,[0,0.12,0],[1,1,1]);
ctx.putImageData(pixels, 0, 0);
};
img.src = 'Hand.png';
HTML
<canvas id="myCanvas" width="638" height="475"></canvas>
Output
It could be further improved by removing noise from the picture to try to clean up the edges.

There are a few mistakes in your code :
The last line a = 0 does nothing but changing a local variable. You have to modify it directly in the array
After that, to see the result, you have to push back the pixel array to the context
Since you need (in that example) to check for white/gray background (rgb(255, 255, 255)), you need to check if the value of the pixel is superior, not inferior. And using a and operator instead of or allows you here to filter a bigger part of the shadow (which is gray so every colour component has almost the same value) without removing the hand itself, which is more coloured.
Here is an example :
var imgData = context.getImageData(0, 0, canvas.width, canvas.height);
for (i = 0; i < imgData.width * imgData.height * 4; i += 4) {
var r = imgData.data[i + 0];
var g = imgData.data[i + 1];
var b = imgData.data[i + 2];
var a = imgData.data[i + 3];
// compare rgb levels for green and set alphachannel to 0;
selectedR = 105;
selectedG = 105;
selectedB = 105;
if (r >= selectedR && g >= selectedG && b >= selectedB) {
imgData.data[i + 3] = 0;
}
}
context.putImageData(imgData, 0, 0);
That still isn't perfect because of the shadow, but it works.

Javascript - Sort rgb values

Using javascript/jquery, I want to sort an array of rgba values to the colours of the visible spectrum. By doing this, like shades should be bunched together. Is there a plugin to do this or how would I go about doing it?
Spectrum image: http://www.gamonline.com/catalog/colortheory/images/spectrum.gif

Disclosure: I'm the author of the library recommended below.
If you don't mind using a library, here's a much more concise version of Oriol's detailed response. It uses the sc-color library:
var sorted = colorArray.sort(function(colorA, colorB) {
return sc_color(colorA).hue() - sc_color(colorB).hue();
});

If your array of colors is like this:
var rgbArr = [c1, c2, c3, ...]
where each color ci is an array of three numbers between 0 and 255
ci = [red, green, blue]
then, you can use this function to convert the colors to HSL
function rgbToHsl(c) {
var r = c[0]/255, g = c[1]/255, b = c[2]/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 new Array(h * 360, s * 100, l * 100);
}
and sort them by hue
var sortedRgbArr = rgbArr.map(function(c, i) {
// Convert to HSL and keep track of original indices
return {color: rgbToHsl(c), index: i};
}).sort(function(c1, c2) {
// Sort by hue
return c1.color[0] - c2.color[0];
}).map(function(data) {
// Retrieve original RGB color
return rgbArr[data.index];
});
Here is a runnable example (thanks Ionică Bizău):
function display(container, arr) {
container = document.querySelector(container);
arr.forEach(function(c) {
var el = document.createElement("div");
el.style.backgroundColor = "rgb(" + c.join(", ") + ")";
container.appendChild(el);
})
}
function rgbToHsl(c) {
var r = c[0] / 255,
g = c[1] / 255,
b = c[2] / 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 new Array(h * 360, s * 100, l * 100);
}
var rgbArr = [];
for (var i = 0; i < 100; ++i) {
rgbArr.push([
Math.floor(Math.random() * 256),
Math.floor(Math.random() * 256),
Math.floor(Math.random() * 256)
]);
}
display("#before", rgbArr);
var sortedRgbArr = rgbArr.map(function(c, i) {
// Convert to HSL and keep track of original indices
return {color: rgbToHsl(c), index: i};
}).sort(function(c1, c2) {
// Sort by hue
return c1.color[0] - c2.color[0];
}).map(function(data) {
// Retrieve original RGB color
return rgbArr[data.index];
});
display("#after", sortedRgbArr);
#before > div,
#after > div {
width: 1%;
height: 20px;
display: inline-block;
}
Random colors: <div id="before"></div>
Same colors, sorted by hue: <div id="after"></div>
sortedRgbArr will contain the rgb colors of rgbArr sorted more or less like the colors of the visible spectrum.
The problem is that the HSL spectrum looks like this:
Your spectrum is weird because it doesn't have all colors, such as pink.
I guess that's because pink doesn't exist in the nature, it's a combination of the colors of the opposite extremes of light's spectrum. But we have it in rgb, so you have to decide where do you want it.
Moreover, it seems that your spectrum goes from lower to higher wavelength, not frequency. But then your spectrum is a reverse of HSL's spectrum.
Replace c1.color[0] - c2.color[0] with c2.color[0] - c1.color[0] if you want it like your spectrum.

JavaScript Calculate brighter colour

I have a colour value in JS as a string
#ff0000
How would I go about programatically calculating a brighter/lighter version of this colour, for example #ff4848, and be able to calculate the brightness via a percentage, e.g.
increase_brightness('#ff0000', 50); // would make it 50% brighter

function increase_brightness(hex, percent){
// strip the leading # if it's there
hex = hex.replace(/^\s*#|\s*$/g, '');
// convert 3 char codes --> 6, e.g. `E0F` --> `EE00FF`
if(hex.length == 3){
hex = hex.replace(/(.)/g, '$1$1');
}
var r = parseInt(hex.substr(0, 2), 16),
g = parseInt(hex.substr(2, 2), 16),
b = parseInt(hex.substr(4, 2), 16);
return '#' +
((0|(1<<8) + r + (256 - r) * percent / 100).toString(16)).substr(1) +
((0|(1<<8) + g + (256 - g) * percent / 100).toString(16)).substr(1) +
((0|(1<<8) + b + (256 - b) * percent / 100).toString(16)).substr(1);
}
/**
* ('#000000', 50) --> #808080
* ('#EEEEEE', 25) --> #F2F2F2
* ('EEE , 25) --> #F2F2F2
**/

Update
#zyklus's answer is simpler and has the same effect. Please refer to this answer only if you are interested in converting between RGB and HSL.
To set the brightness of RGB:
Convert RGB to HSL
Set the brightness of HSL
Convert back from HSL to RGB
This link used to have code to convert RGB to HSL and reverse:
http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
/**
* 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];
}
I made some example with it. Check this link: http://jsfiddle.net/sangdol/euSLy/4/
And this is the increase_brightness() function:
function increase_brightness(rgbcode, percent) {
var r = parseInt(rgbcode.slice(1, 3), 16),
g = parseInt(rgbcode.slice(3, 5), 16),
b = parseInt(rgbcode.slice(5, 7), 16),
HSL = rgbToHsl(r, g, b),
newBrightness = HSL[2] + HSL[2] * (percent / 100),
RGB;
RGB = hslToRgb(HSL[0], HSL[1], newBrightness);
rgbcode = '#'
+ convertToTwoDigitHexCodeFromDecimal(RGB[0])
+ convertToTwoDigitHexCodeFromDecimal(RGB[1])
+ convertToTwoDigitHexCodeFromDecimal(RGB[2]);
return rgbcode;
}
function convertToTwoDigitHexCodeFromDecimal(decimal){
var code = Math.round(decimal).toString(16);
(code.length > 1) || (code = '0' + code);
return code;
}
You can pass a negative value as a percent argument to make it darken.

In case anyone needs it, I converted the color brightness JavaScript code to ASP / VBScript for a project and thought I would share it with you:
'::Color Brightness (0-100)
'ex. ColorBrightness("#FF0000",25) 'Darker
'ex. ColorBrightness("#FF0000",50) 'Mid
'ex. ColorBrightness("#FF0000",75) 'Lighter
Function ColorBrightness(strRGB,intBrite)
strRGB = Replace(strRGB,"#","")
r = CInt("&h" & Mid(strRGB,1,2))
g = CInt("&h" & Mid(strRGB,3,2))
b = CInt("&h" & Mid(strRGB,5,2))
arrHSL = RGBtoHSL(r, g, b)
dblOrigBrite = CDbl(arrHSL(2) * 100)
arrRGB = HSLtoRGB(arrHSL(0), arrHSL(1), intBrite/100)
newRGB = "#" & HEXtoDEC(arrRGB(0)) & HEXtoDEC(arrRGB(1)) & HEXtoDEC(arrRGB(2))
ColorBrightness = newRGB
End Function
'::RGB to HSL Function
Function RGBtoHSL(r,g,b)
r = CDbl(r/255)
g = CDbl(g/255)
b = CDbl(b/255)
max = CDbl(MaxCalc(r & "," & g & "," & b))
min = CDbl(MinCalc(r & "," & g & "," & b))
h = CDbl((max + min) / 2)
s = CDbl((max + min) / 2)
l = CDbl((max + min) / 2)
If max = min Then
h = 0
s = 0
Else
d = max - min
s = IIf(l > 0.5, d / (2 - max - min), d / (max + min))
Select Case CStr(max)
Case CStr(r)
h = (g - b) / d + (IIf(g < b, 6, 0))
Case CStr(g)
h = (b - r) / d + 2
Case CStr(b)
h = (r - g) / d + 4
End Select
h = h / 6
End If
RGBtoHSL = Split(h & "," & s & "," & l, ",")
End Function
'::HSL to RGB Function
Function HSLtoRGB(h,s,l)
If s = 0 Then
r = l
g = l
b = l
Else
q = IIf(l < 0.5, l * (1 + s), l + s - l * s)
p = 2 * l - q
r = HUEtoRGB(p, q, h + 1/3)
g = HUEtoRGB(p, q, h)
b = HUEtoRGB(p, q, h - 1/3)
End If
HSLtoRGB = Split(r * 255 & "," & g * 255 & "," & b * 255, ",")
End Function
'::Hue to RGB Function
Function HUEtoRGB(p,q,t)
If CDbl(t) < 0 Then t = t + 1
If CDbl(t) > 1 Then t = t - 1
If CDbl(t) < (1/6) Then
HUEtoRGB = p + (q - p) * 6 * t
Exit Function
End If
If CDbl(t) < (1/2) Then
HUEtoRGB = q
Exit Function
End If
If CDbl(t) < (2/3) Then
HUEtoRGB = p + (q - p) * (2/3 - t) * 6
Exit Function
End If
HUEtoRGB = p
End Function
'::Hex to Decimal Function
Function HEXtoDEC(d)
h = Hex(Round(d,0))
h = Right(String(2,"0") & h,2)
HEXtoDEC = h
End Function
'::Max Function
Function MaxCalc(valList)
valList = Split(valList,",")
b = 0
For v = 0 To UBound(valList)
a = valList(v)
If CDbl(a) > CDbl(b) Then b = a
Next
MaxCalc = b
End Function
'::Min Function
Function MinCalc(valList)
valList = Split(valList,",")
For v = 0 To UBound(valList)
a = valList(v)
If b = "" Then b = a
If CDbl(a) < CDbl(b) AND b <> "" Then b = a
Next
MinCalc = b
End Function
'::IIf Emulation Function
Function IIf(condition,conTrue,conFalse)
If (condition) Then
IIf = conTrue
Else
IIf = conFalse
End If
End Function

That way you won't need any conversion of the source color.
check out this fiddle : https://jsfiddle.net/4c47otou/
increase_brightness = function(color,percent){
var ctx = document.createElement('canvas').getContext('2d');
ctx.fillStyle = color;
ctx.fillRect(0,0,1,1);
var color = ctx.getImageData(0,0,1,1);
var r = color.data[0] + Math.floor( percent / 100 * 255 );
var g = color.data[1] + Math.floor( percent / 100 * 255 );
var b = color.data[2] + Math.floor( percent / 100 * 255 );
return 'rgb('+r+','+g+','+b+')';
}
Example usage :
increase_brightness('#0000ff',20);
increase_brightness('khaki',20);
increase_brightness('rgb(12, 7, 54)',20);

// color is a hex color like #aaaaaa and percent is a float, 1.00=100%
// increasing a color by 50% means a percent value of 1.5
function brighten(color, percent) {
var r=parseInt(color.substr(1,2),16);
var g=parseInt(color.substr(3,2),16);
var b=parseInt(color.substr(5,2),16);
return '#'+
Math.min(255,Math.floor(r*percent)).toString(16)+
Math.min(255,Math.floor(g*percent)).toString(16)+
Math.min(255,Math.floor(b*percent)).toString(16);
}
Live sample: http://jsfiddle.net/emM55/

Here is the increaseBrightness function with the RGB->HSL->RGB method. "amount" should be in percent.
HSL<->RGB conversion functions taken from http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
function increaseBrightness( color, amount ) {
var r = parseInt(color.substr(1, 2), 16);
var g = parseInt(color.substr(3, 2), 16);
var b = parseInt(color.substr(5, 2), 16);
hsl = rgbToHsl( r, g, b );
hsl.l += hsl.l + (amount / 100);
if( hsl.l > 1 ) hsl.l = 1;
rgb = hslToRgb( hsl.h, hsl.s, hsl.l );
var v = rgb.b | (rgb.g << 8) | (rgb.r << 16);
return '#' + v.toString(16);
}
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':h, 's':s, 'l':l};
}
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':r * 255, 'g':g * 255, 'b':b * 255 };
}

I found a variation of Sanghyun Lee's reply generates the best result.
Convert RGB to HSL
Set the brightness of HSL
Convert back from HSLto RGB
The difference/variation is how you increase/decrease the brightness.
newBrightness = HSL[2] + HSL[2] * (percent / 100) // Original code
Instead of applying a percentage on the current brightness, it works better if it is treated as absolute increment/decrement. Since the luminosity range is 0 to 1, the percent can be applied on the whole range (1 - 0) * percent/100.
newBrightness = HSL[2] + (percent / 100);
newBrightness = Math.max(0, Math.min(1, newBrightness));
Another nice property of this approach is increment & decrement negate each other.
Image below shows darker and lighter colors with 5% increment. Note, how the palette is reasonably smooth and often ends with black and white.
Palette with original approach - gets stuck at certain colors.

I know this an old question, but I found no answer that simply manipulates css hsl color. I found the old answers here to be too complex and slow, even producing poor results, so a different approach seems warranted. The following alternative is much more performant and less complex.
Of course, this answer requires you to use hsl colors throughout your app, otherwise you still have to do a bunch of conversions! Though, if you need to manipulate brightness eg in a game loop, you should be using hsl values anyway as they are much better suited for programmatic manipulation. The only drawback with hsl from rgb as far as I can tell, is that it's harder to "read" what hue you're seeing like you can with rgb strings.
function toHslArray(hslCss) {
let sep = hslCss.indexOf(",") > -1 ? "," : " "
return hslCss.substr(4).split(")")[0].split(sep)
}
function adjustHslBrightness(color, percent) {
let hsl = toHslArray(color)
return "hsl(" + hsl[0] + "," + hsl[1] + ", " + (percent + "%") + ")"
}
let hsl = "hsl(200, 40%, 40%)"
let hsl2 = adjustHslBrightness(hsl, 80)

function brighten(color, c) {
const calc = (sub1,sub2)=> Math.min(255,Math.floor(parseInt(color.substr(sub1,sub2),16)*c)).toString(16).padStart(2,"0")
return `#${calc(1,2)}${calc(3,2)}${calc(5,2)}`
}
const res = brighten("#23DA4C", .5) // "#116d26"
console.log(res)

What I use:
//hex can be string or number
//rate: 1 keeps the color same. < 1 darken. > 1 lighten.
//to_string: set to true if you want the return value in string
function change_brightness(hex, rate, to_string = false) {
if (typeof hex === 'string') {
hex = hex.replace(/^\s*#|\s*$/g, '');
} else {
hex = hex.toString(16);
}
if (hex.length == 3) {
hex = hex.replace(/(.)/g, '$1$1');
} else {
hex = ("000000" + hex).slice(-6);
}
let r = parseInt(hex.substr(0, 2), 16);
let g = parseInt(hex.substr(2, 2), 16);
let b = parseInt(hex.substr(4, 2), 16);
let h, s, v;
[h, s, v] = rgb2hsv(r, g, b);
v = parseInt(v * rate);
[r, g, b] = hsv2rgb(h, s, v);
hex = ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);
if (to_string) return "#" + hex;
return parseInt(hex, 16);
}
function rgb2hsv(r,g,b) {
let v = Math.max(r,g,b), n = v-Math.min(r,g,b);
let h = n && ((v === r) ? (g-b)/n : ((v === g) ? 2+(b-r)/n : 4+(r-g)/n));
return [60*(h<0?h+6:h), v&&n/v, v];
}
function hsv2rgb(h,s,v) {
let f = (n,k=(n+h/60)%6) => v - v*s*Math.max( Math.min(k,4-k,1), 0);
return [f(5),f(3),f(1)];
}

A variant with lodash:
// color('#EBEDF0', 30)
color(hex, percent) {
return '#' + _(hex.replace('#', '')).chunk(2)
.map(v => parseInt(v.join(''), 16))
.map(v => ((0 | (1 << 8) + v + (256 - v) * percent / 100).toString(16))
.substr(1)).join('');
}

First get a quick understanding of hex color codes.
Then it should be pretty easy to break down your color value into RGB, make the adjustments and then return the new color code.

Why doesn't this Javascript RGB to HSL code work?

I found this RGB to HSL script over at http://www.mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript. I can't find any other small decent ones. The issue is that this code doesn't even really work. Would anybody know why? (I don't know a bit of color math, but maybe it's returning the complementary?)
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];
}
Edit: when I run rgbToHsl(126,210,22) it's giving me [ .24, .81, .45 ], which is the HSL for an orange color.

The resulting HSV array has to be interpreted as three fractions. For some programs, if you want to express HSV as integers, you multiply the "H" value by 360 and the "S" and "V" values by 100. The HSV value you quote for your green shade RGB[126, 210, 22] is HSV [87, 81, 45] in integers. You could change the function to return such integers if you want to:
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 [Math.floor(h * 360), Math.floor(s * 100), Math.floor(l * 100)];
}
[edit] that said, it's still giving me something with a brightness ("L" or "V") that's considerably too dark; Gimp says that the HSV value should be [90, 80, 82], or in fractional terms [.20, .80, .82].
[another edit] well one problem could be that HSL and HSV are different schemes ... still looking around.
OK in case anybody wants RGB to HSV (like you'd see in Gimp for example) here's a version of that:
function rgbToHsv(r, g, b) {
var
min = Math.min(r, g, b),
max = Math.max(r, g, b),
delta = max - min,
h, s, v = max;
v = Math.floor(max / 255 * 100);
if ( max != 0 )
s = Math.floor(delta / max * 100);
else {
// black
return [0, 0, 0];
}
if( r == max )
h = ( g - b ) / delta; // between yellow & magenta
else if( g == max )
h = 2 + ( b - r ) / delta; // between cyan & yellow
else
h = 4 + ( r - g ) / delta; // between magenta & cyan
h = Math.floor(h * 60); // degrees
if( h < 0 ) h += 360;
return [h, s, v];
}
edit note that a couple comments suggest that Math.round() might give better answers than Math.floor(), if anybody wants to experiment.

Short but precise
It looks that your code is ok (but it returns hue=0.24 - multiply this by 360 degree to get angle integer value) - however Try this shorter one ( more: hsl2rgb, rgb2hsv, hsv2rgb and sl22sv):
// in: r,g,b in [0,1], out: h in [0,360) and s,l in [0,1]
function rgb2hsl(r,g,b) {
let v=Math.max(r,g,b), c=v-Math.min(r,g,b), f=(1-Math.abs(v+v-c-1));
let h= c && ((v==r) ? (g-b)/c : ((v==g) ? 2+(b-r)/c : 4+(r-g)/c));
return [60*(h<0?h+6:h), f ? c/f : 0, (v+v-c)/2];
}
function rgb2hsl(r,g,b) {
let v=Math.max(r,g,b), c=v-Math.min(r,g,b), f=(1-Math.abs(v+v-c-1));
let h= c && ((v==r) ? (g-b)/c : ((v==g) ? 2+(b-r)/c : 4+(r-g)/c));
return [60*(h<0?h+6:h), f ? c/f : 0, (v+v-c)/2];
}
console.log(`rgb: (0.36,0.3,0.24) --> hsl: (${rgb2hsl(0.36,0.3,0.24)})`);
// ---------------
// UX
// ---------------
rgb= [0,0,0];
hs= [0,0,0];
let $ = x => document.querySelector(x);
let hsl2rgb = (h,s,l, a=s*Math.min(l,1-l), f= (n,k=(n+h/30)%12) => l - a*Math.max(Math.min(k-3,9-k,1),-1)) => [f(0),f(8),f(4)];
function changeRGB(i,e) {
rgb[i]=e.target.value/255;
hs = rgb2hsl(...rgb);
refresh();
}
function changeHS(i,e) {
hs[i]=e.target.value/(i?255:1);
rgb= hsl2rgb(...hs);
refresh();
}
function refresh() {
rr = rgb.map(x=>x*255|0).join(', ')
tr = `RGB: ${rr}`
th = `HSL: ${hs.map((x,i)=>i? (x*100).toFixed(2)+'%':x|0).join(', ')}`
$('.box').style.backgroundColor=`rgb(${rr})`;
$('.infoRGB').innerHTML=`${tr}`;
$('.infoHS').innerHTML =`${th}`;
$('#r').value=rgb[0]*255;
$('#g').value=rgb[1]*255;
$('#b').value=rgb[2]*255;
$('#h').value=hs[0];
$('#s').value=hs[1]*255;
$('#l').value=hs[2]*255;
}
refresh();
.box {
width: 50px;
height: 50px;
margin: 20px;
}
body {
display: flex;
}
<div>
<input id="r" type="range" min="0" max="255" oninput="changeRGB(0,event)">R<br>
<input id="g" type="range" min="0" max="255" oninput="changeRGB(1,event)">G<br>
<input id="b" type="range" min="0" max="255" oninput="changeRGB(2,event)">B<br>
<pre class="infoRGB"></pre>
</div>
<div>
<div class="box hsl"></div>
</div>
<div>
<input id="h" type="range" min="0" max="360" oninput="changeHS(0,event)">H<br>
<input id="s" type="range" min="0" max="255" oninput="changeHS(1,event)">S<br>
<input id="l" type="range" min="0" max="255" oninput="changeHS(2,event)">L<br>
<pre class="infoHS"></pre><br>
</div>
I develop S_HSL wiki formulas (marked by green border) - where MAX=max(r,g,b) and MIN=min(r,g,b) - and in above code I make some improvements and make analysis which shows that results are correct. This allows me to get quite short code at the end

Function below converts RGB color into Hue Saturation Brightness color like Photoshop color picker, results are in the ranges:
Hue 0-360 (degrees)
Saturation: 0-100 (%)
Brightness: 0-100 (%)
I still don't understand why people use the term HSV (Hue Saturation Value) instead of HSB (Hue Saturation Brightness), anyway it's a matter fo terminology, the results are the same
//Converts to color HSB object (code from here http://www.csgnetwork.com/csgcolorsel4.html with some improvements)
function rgb2hsb(r, g, b)
{
r /= 255; g /= 255; b /= 255; // Scale to unity.
var minVal = Math.min(r, g, b),
maxVal = Math.max(r, g, b),
delta = maxVal - minVal,
HSB = {hue:0, sat:0, bri:maxVal},
del_R, del_G, del_B;
if( delta !== 0 )
{
HSB.sat = delta / maxVal;
del_R = (((maxVal - r) / 6) + (delta / 2)) / delta;
del_G = (((maxVal - g) / 6) + (delta / 2)) / delta;
del_B = (((maxVal - b) / 6) + (delta / 2)) / delta;
if (r === maxVal) {HSB.hue = del_B - del_G;}
else if (g === maxVal) {HSB.hue = (1 / 3) + del_R - del_B;}
else if (b === maxVal) {HSB.hue = (2 / 3) + del_G - del_R;}
if (HSB.hue < 0) {HSB.hue += 1;}
if (HSB.hue > 1) {HSB.hue -= 1;}
}
HSB.hue *= 360;
HSB.sat *= 100;
HSB.bri *= 100;
return HSB;
}
Usage example:
var hsb = rgb2hsb(126,210,22);
alert("hue = " + hsb.hue + "saturation = " + hsb.sat + "brightness = " + hsb.bri);

You have to change to the hsl format just like hsl(155,100%,30%), that can be use in HTML.
//this change hsl to : "hsl(155,100%,30%)"
function hsl2str({h,s,l,a=1}) {
return "hsl("+h+","+s*100+"%,"+l*100+"%,"+a+")";
}
//for html, the h is 0-360, so you need this function
function rgb2hsl({r,g,b,a=1}) {
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;
}
}
return {h: h*60,s,l,a};
}