[Cheeseh]

Doing what you are proposing isn't very easy for what you want to do, it would require pattern recognition and high intelligence to find points of interest on the screen. If there is only colour required to determine health (and it is on a static point on a screen continuously) then it might be easier but I dont know what functions you'll need exactly... Running through each pixel wont be very good either because youll run through millions of pixels and most likely suffer frame glitches during the game.

Best way is to find an API into the game, if none is available try hacking into the game to find the memory location offsets of the health/"co-ordinates" or whatever, you can find these quite easily with a trial & error approach by using a program such as GameHack or your own built program.

if its a windows program, i think there are methods of retrieving colour information, could update the information each time WM_PAINT message is called (as long as the method is trivial), you can also send messages, keys or other information I believe by using SendMessage() into the window.