I would like to use PyQT or PyGTK (or any other suitable framework if there is better one) to do the following:

1. Load a picture (PNG possibly, although other formats too if easy)
2. Pan and Zoom the loaded picture
3. Use stylus to click anywhere on the picture and get the coordinates of that specific point
4. Overlay another picture on top of the original one

(3) above is the most important one, and it the one I need the most help with. For now I have no clue whatsoever, although I am still searching.
Would also appreciate hints/pointers on the other ones too if possible

Modify Mypaint.

Thanks, yes I had already downloaded the source of MyPaint. However it's quite a huge thing and my py-fu isn't at all level yet