Hi, for a program, I need to map the location of all the back pixels in an image into some kind of structure. The program later uses the structure to select a random pixel location. It then removes the location, to prevent it being used again. The problem is, there is a huge number of black pixels (close to 40,000) so an ordinary array takes forever to search for and eliminate the "used" pixels. Is there some other "Faster" data structure?