Color Luminance

ColorLuminance.js

/*
This is the solution that I use in my projects for dynamic colors.
Don't know where I got it.

ColorLuminance("#69c", 0);       // returns "#6699cc"
ColorLuminance("6699CC", 0.2);  // "#7ab8f5" - 20% lighter
ColorLuminance("69C", -0.5);    // "#334d66" - 50% darker
ColorLuminance("000", 1);       // "#000000" - true black cannot be made lighter!

Real life example:
function getCityColor(mainColor, maxVote, votePercentage)
{
    var result = "#E8DFD9"; // default
    var lightningStep = 0.1;
    var currentLightning = 0;
    var step = 5;

    for(var i = parseInt(maxVote); i > 0; i = i - step)
    {
        if(votePercentage > i)
        {
            result = ColorLuminance(mainColor, currentLightning);
            break;
        }
        else
        {
            currentLightning += lightningStep;
        }
    }

    return result;
}
*/

function ColorLuminance(hex, lum) {

    // validate hex string
    hex = String(hex).replace(/[^0-9a-f]/gi, '');
    if (hex.length < 6) {
        hex = hex[0]+hex[0]+hex[1]+hex[1]+hex[2]+hex[2];
    }
    lum = lum || 0;

    // convert to decimal and change luminosity
    var rgb = "#", c, i;
    for (i = 0; i < 3; i++) {
        c = parseInt(hex.substr(i*2,2), 16);
        c = Math.round(Math.min(Math.max(0, c + (c * lum)), 255)).toString(16);
        rgb += ("00"+c).substr(c.length);
    }

    return rgb;
}