Watching a QImage during single-stepping

I'm debugging a huge Qt app with hundreds of classes, messy code, etc. While tracking down a bug, I want to single-step in gdb (kdbg, ddd, whatever) while watching what gets drawn into a QImage using a QPainter that's carried about from method to method. Somewhere, it's doing being given bad information. Normally all I can get is the final QImage written to a .png file.

Is there some way to see what the image is in a QImage when stopped in a de开发者_运维百科bugger?

BTW, this is using Qt4.3, which is kinda old but we're stuck with for now. If a newer Qt offers some advantage, I have ways to hack with it (as well as others seeing this question may have the latest).

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That's one of the examples in the Peek and Poke, Vol. 3 article on Qt Labs blog.