Way to script manual rectangle definition?

[Ofnuts]

You cannot have a GUI interaction  in a script. Typically you would ask the user to define the rectangle before calling your script.

If you have to process many pictures in sequence, you can do this:

1. load the first image and do the initial processing
   
2. let the user define the square
   
3. run a second script that:
   • does the second part of the process
     
   • saves/exports the image
     
   • loads the next image and does the initial processing
     
4. go to step 2
   

Then the script #1 is run once, and script #2 is run once for each image: except for the first, you have only one interaction per image. For an example see my ofn-file-next script.