Scale crop frame by percentage feature

Hi all, I am experimenting with a feature to scale the crop frame by a user-specified percentage.

Screenshot 2023-07-10 213239

My goal is to be able to crop an image for digital display, but then to also produce a slightly larger crop for full-bleed printing.

See my related Issue on github here: Scale Crop Frame by Percentage · Issue #6791 · Beep6581/RawTherapee (github.com)

In the issue page, I also explained that I think my goal could be achieved different ways, such as by adding a new “frame within a frame” crop guide type.

I just wanted to open discussion about this to see what other people think before writing any more code. Thank you for reading!