If you are talking about screenshots then unfortunately last I heard they did away with the SAVE IMAGE command in DB Pro (which is horribly short sighted of them) but there might be a .dll that you can use. If you are talking about capturing an image of the user's desktop then I don't think you can.
You can do a pixel by pixel comparison between two images to see if they match up. Use the POINT command to get the colour value of each pixel and store them in 2 screen sized arrays (ie.
DIM screen_1(800,600) ) and then compare the values (ie.
IF screen_2(1,1) = screen_1(1,1) THEN match = 1 ).
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