The problem with graphics though is that some graphical operations are destructive so you can't just undo the operation. In order to undo without a redo list,

The problem with graphics though is that some graphical operations are destructive so you can't just undo the operation. In order to undo without a redo list, you would have to keep a complete graphical representation of the image and each operation. With images the memory usage goes up very quickly in that case, copying large blocks of memory on each operation makes your image editing slow down too.