Thanks Manfred, that is what I am doing at present and its works but slowly. I have also found that a screenshot is device dependent ie. The pixel information for the same point on my mobile is not the same as on my tablet (the RGB values are different). I am working on a way to calibrate the system but I had hoped for a more direct approach, reading the screen in the hope that this problem would be fixed. I am not even sure why there is a difference in the bitmaps. I have probably overlooked something.