an example can be found on AMOSPro_Examples:Examples/H-6/Help_66.AMOS
Gets a rectangular screen BLOCK from the screen, and compresses it as much as possible as it's being saved into memory.
Get Cblock n,x,y,width,height
Grabs a block with number n from x,y to x+w,y+h on the current screen. Note that x and w are automatically rounded down to the nearest multiple of eight.