Version:            (using KDE 4.2.90)

When you zoom in image, and then you scroll it, you can scroll it in such way that left edge of the image will be left edge of the screen. But it is the limit, you cannot scroll more. 

However when you are working in such areas, it is more useful to place image in more comfortable position (after all when you paint on the paper, you usually move the paper at the center of the desk, not at the edge) -- i.e. the center of the screen.

So, please let the user to scroll the image with extended limits (bigger margins) in such way, that user could scroll image to see left edge of the image at the center of the screen (and the same for all other edges and corners).