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 开发者_JAVA技巧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:

1. Convert RGB to HSL

2. Set the brightness of HSL

3. 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.

1. Convert RGB to HSL
2. Set the brightness of HSL
3. 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.