During reading of the XML, some changes after reading in the intrinsic parameters trigger on_*_valueChanged slots and in these updateImage is called. Since to this point it's still the old image, CalibFilter creates maps with the size of the old image. And since the intrinsic parameters were already set, afterwards the cached, too small, mappings were used.
To catch that, I invalidate the cache on a map with a different size than the image.
I don't know if the rest is working when loading in a new project. But I see no incredibly obvious mistakes. Relates #4 (closed)