Background luminescence detection

Background luminescence detection! So you can determine wither you need a white colored font or a black colored font based on the background image.

Got an idea that 7.0 can do this since I've seen status bar icons and the clock on the lock screen font color go black when there is a light color background.

In a nutshell interrogate the current background for it's luminescence and make a decision whether black or white would be the best font color against that background.