I like the Program - It appears to be very quick and good codet as well.
But - please - don't make the same mistake like adobe does in photoshop.
Give the User the ability to dock the toolboxes on the right or left or top window-corner. Otherwise the toolboxes will ever overlapp the image. i hate this in photoshop.
i recognized that the toolboxes moves a bit if a scrollbar appears for scrolling the image - that's not a bad thing, but a much more better thing would be to let the toolboxes dock at the corners if somebody want's that - so that the image-window stops where the toolbox-corner begins.
Thanks!