Version: (using Devel) Compiler: gcc4.3.2 OS: Linux Installed from: Compiled sources New option 'inverse transformation' is very, very good thing for simple perspective adjustments but has one bug: it badly guesses aspect ratio of corrected fragment. With author's purpose of correcting paintings to get rid of frames it isn't very important but if fails badly even with example presented on his blog: http://zwabel.wordpress.com/2009/04/06/kde-for-painters Selected area is visibly rectangular but output is almost square. To correct this user have to perform additional transformation with all - bad - consequences for image quality.
Authors response for this question on his blog: " Yes, it maybe could do a better job in this. But I think it’s not possible to reliably guess the real proportion, because you never know whether what parts of the proportion come from the perspective transformation, and what is part of the image. So it just takes the bounding-rect of the transformed version right now. " After more tests I have to agree. Closing. Sorry for noise.