Video/Image Mixer

I have a port of the VIP suite video demo for the NEEK right now. In the video processing chain, there is a mixer which takes in the video signal on one channel and the output from a test pattern generator on the other. I would like to be able to replace that test pattern generator and use a bitmap image as the background instead of the test pattern. Can anyone tell me what the simplest way is to get a bitmap from the flash memory into that mixer channel?