I'm trying to find a method for determining whether to use black or white text, given a background color (as a hex value). Has anyone dealt with this before? Is there an effective way to do this?
In my case, I would be using PHP to implement the logic (though any experience with this in other languages is welcome).
A simple but not perfect solution would be to sum the individual components (RGB) and the larger this value the 'lighter the color'. So for a high value you could use black as the foreground, and for a low value, use white.
You could then improve this method, making specific cases for greyscale colors (R = G = B), which, except for very dark grey, won't display white text well.
Edit: This of course means you need to know the format of RGB storage in your hex value, standard 24bpp storage is 0x00RRGGBB for the 8 hex digits.
Take a look at this page: Calculating Color Contrast with PHP
Keep in mind that if black and white are your only choices you're bound to have cases where neither of them works particularly great.
i would calculate the average value of rgb components and then decide whether to use black or white, e.g. white up to 0x66
Here is an algorithm that can be used to calculate a luminosity contrast ratio of your text:
http://juicystudio.com/services/aertcolourcontrast.php
You could use this formula with white and black values to calculate which gives you the higher ratio, and thus more readable text.