It all depends on what kind of image processing tasks you need to do. The best place to start is probably OpenCV. I'm sure it's possible to at least try to get it working on a DSP (with uCLinux for example). Otherwise, you can at least have access to the source of the algorithms you need and copy them into your DSP code. I recommend you try to get a micro-linux distro running on your DSP that's going to be the easiest when trying to port or use any 3rd party library.