jQuery: Change text color based on containing element's background color?

Question

I want to change the text color of an element based on the element's background color.

For instance, if the background color is changed to black, then make the text white. If the background color is changed to white, then make the text black.

It'd be a bit more complex than than that though as the user can change the background color to whatever they'd like.

I found some random articles about handling it on the backend, but nothing using javascript (or better yet, jQuery).

Answer 1

First, create a function that determines whether a color is dark or not (source, modified):

function isDark( color ) {
    var match = /rgb\((\d+).*?(\d+).*?(\d+)\)/.exec(color);
    return parseFloat(match[1])
         + parseFloat(match[2])
         + parseFloat(match[3])
           < 3 * 256 / 2; // r+g+b should be less than half of max (3 * 256)
}

Then, use something along the lines of:

$('elem').each(function() {
    $(this).css("color", isDark($(this).css("background-color")) ? 'white' : 'black');
});

http://jsfiddle.net/QkSva/