Well, you could use Image to Array to "reduce" the Image to an N by M array of intensities (corresponding to your Pixels), use Array functions to split the Array however you want, then use Array to Image to cast the Array back to a displayable Image. Note that you'll need additional Image buffers (one per sub-image) to make this work. You can find these functions on the Pixel Manipulation sub-palette.
Bob Schor
