Topic: Frequency Domain filter improvement
First, thanks for this awesome tool, it's irreplaceable when dealing with badly scanned images and removing pattern noise. Not even specialized noise removal tools can achieve decent results without image being pre-filtered by FDF.
However this tool remains not very user-friendly, so I thought of a couple of ideas that could improve working experience. I tried to put them in order from most wanted to least important or too difficult.
Internal undo ability.
Since constructing and reconstructing image from/to its FD takes significant time and also because FD is itself an editor, I think it could be reasonable to have an ability to undo previous use of Pen, so that one wrong move won't spoil all the work done prior to it.
Feather for the Pen. So far Pen tool simply cuts out part of FD image, leaving sharp edges around the area. As you might know, such edges lead to ringing artifacts on resulting image around its sharp edges. Also, usually unwanted frequencies from pattern noise represent themselves on FD as a star with some halo around it, gradually darker with distance, so feathered Pen will be suitable for removing this. If it is impossible to implement "half-tones" when erasing part of FD, I think it could be implemented with something similar to MSPaint's "Airbrush" - instead of feather use random dots around the Pen, closer to Pen - more the dots. I now have to implement this kind of "feather" myself by setting Pen size to 1 and randomly moving it around needed area.
Mirror Pen actions. Very often pattern noise on scanned images is almost identical on left and right sides of FD representation. We could save 1/2 of time spent on its removal by working only with one half and reflecting changes on the other.
Scaling up FD window contents. It's no problem working at far corners of FD, but the closer we get to the top center, the lower and more significant frequencies are affected and this needs some precision. Ability to scale FD image like any other picture would help a lot.
Lowering resolution of visible FD image. I noticed, that the size of the FD window doesn't depend on source image dimensions, but the speed of interaction with it does. Since we can't squeeze all the information into fixed size window, it would make sense to downscale it to some extent - after all we can't talk about any precision work in default window size mode for which full resolution representation could be needed (Actual Frequency information in RAM would be intact). In fact, speedup gained from this will improve the precision by decreasing editor's response time. This could also be somehow joined with previous ability, or at least one of them would be fine.
Place window focus at "Pen size" edit field upon opening of FD window. This will save a user one click - not much, but mouse wheel doesn't have any other use there anyway, and this shouldn't be very difficult to implement.
I also have some thoughts regarding automating frequency peaks removal, but my post is already big and too demanding. Sorry for that, I just wanted to give some food for thought about improvement of the tool I use the most for a long time.