How do I change text-color determined by the background color?

I'm looking for a way, with jQuery ideally, to determine 开发者_运维百科the correct text color, based on the brightness of the background color?

E.g. white background, black text colour. I believe this could be done crudely with adding the HEX value and guesstimating but does anyone know a better way or jQuery way to do this?

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You can try inverting the hex value of the color. So #FFFFFF becomes #000000 and #AAAAAA becomes #555555. Of course, this method falls through when you have #888888 which when inverted, gives you #777777 (they don't contrast as much).

This blog post describes another way (they only use black or white for the foreground color, depending on the background color). I've translated it into Javascript:

function idealTextColor(bgColor) {

   var nThreshold = 105;
   var components = getRGBComponents(bgColor);
   var bgDelta = (components.R * 0.299) + (components.G * 0.587) + (components.B * 0.114);

   return ((255 - bgDelta) < nThreshold) ? "#000000" : "#ffffff";   
}

function getRGBComponents(color) {       

    var r = color.substring(1, 3);
    var g = color.substring(3, 5);
    var b = color.substring(5, 7);

    return {
       R: parseInt(r, 16),
       G: parseInt(g, 16),
       B: parseInt(b, 16)
    };
}