In this post is a list of 4 Detect DarkLight Background jQuery Plugins. They are pretty useful for websites with dynamic backgrounds where light is used on dark backgrounds and dark used on light background.
Automatically switch to a darker or a lighter version of an element depending on the brightness of images behind it.
A lightweight and easy-to-use jQuery plugin that determines if the background colour of an element is light or dark.
A simple jQuery plugin to extract the dominant color of an image and apply it to the background of its parent element.
Brightness detection script.