XBImageFilters
XBImageFilters allows you to obtain filtered versions of any image or from the camera in realtime. It uses OpenGL ES 2 to filter the images through fragment shaders you write yourself so you can filter your images in whatever way you want and it is super fast.
In this screenshot of the sample we have on the top half of the screen a regular UIImageView with contentMode set to UIViewContentModeTop, and on the bottom half a XBFilteredImageView with the same image with contentMode set to UIViewContentModeBottom and a filter [a GLSL fragment shader] that outputs the luminance of the pixel color.
Project Status
This project is in a very early stage of development so not all features advertised are functional yet.