Color Counter 1.0

This plug-in counts the colors used in an image. Its pretty simple-minded, so it needs to allocate a big chunk of memory to mark off which colors are in use. (2MB for RGB, 512MB(!) for CMYK.) You can do single channels, too, with very little memory required. It does 16-bit grayscale images, but doesnt even try to do other 16-bit modes.