I've tried a few texture rippers but none have been able to replace shoebox for me but this one is really close and with a few more improvements it will 100% become the recommended tool for people ripping textures.
for me 4 things will make this a perfect replacement for shoebox.
1. Slow mode is nice but for larger texture you still have to wait for it to finish rendering each time you move a point, having a mode where you can move the points then press a button to rip would greatly speedup the process.
2. The ability to drag and drop an image into the program to auto open it would be very useful if possible.
3. When exporting using the input image file name as the export name (With a suffix like "_R") would be handy.
4. A way to click and add points like shoebox would be nice.
Even without these things this tool is already something people should start using instead of Shoebox, keep up the great work.