[jitter] (no subject)

hi

whats the best way to do the following:

i want to read a still image, but not display it immediately. instead  
i want to reveal blocks of it (maybe 10 x 10 pixels at a time)  
scanning from left to right, top to bottom, until the complete image  
is visible.

and this needs to be quite fast too.. like maybe 30ms per block.

thanks
m