Ancow, second method is clear for me, but I don't exactly understand how one can overlay picture from N900 to paper, except that placing paper on N900 screen backlighted, and paint this way. Ho ever, I don't know what this have to do with camera-ui2 - one can just view that image on picture viewer, with backlight enabled all the time.

I don't get what transparency layers on camera-ui2 have to do with drawing on paper.