Javascript - "One Shade Darker"

Question

Is it possible to use javascript to determine which color is one shade darker than the current background? Maybe some kind of hexadecimal addition / subtraction?

I have a menu that can be of any color, and if it weren’t too complicated, it would be great if the submenu could be one shade darker. Does anyone know how to achieve this effect?

Answer 1

as AB comments, the “shade” is not very clearly defined. however, it would be easier to think about it in some other color representation, such as the “V” in hsv .

, v , , v- rgb hex

Answer 2

- :

function shadeColor(color, shade) {
    var colorInt = parseInt(color.substring(1),16);

    var R = (colorInt & 0xFF0000) >> 16;
    var G = (colorInt & 0x00FF00) >> 8;
    var B = (colorInt & 0x0000FF) >> 0;

    R = R + Math.floor((shade/255)*R);
    G = G + Math.floor((shade/255)*G);
    B = B + Math.floor((shade/255)*B);

    var newColorInt = (R<<16) + (G<<8) + (B);
    var newColorStr = "#"+newColorInt.toString(16);

    return newColorStr;
}

:

var newColor = shadeColor("#AA2222", -10);
alert(newColor); //Results in #a32020

: http://pastebin.com/g6phySEv