Mas, I've tried twice to process an image that I successfully processed with the previous version of your excellent script. Moi crashed both time. The original image was 2761x2761 pixels.
It imports OK - I used a scale factor of 7.
I then scaled down to about 1/25 of size to give a 395 curves of xyz of 100 100 5.62.
Then loft OK but MOI locks up when I tried to extrude by -5mm.
I guess that it's run out of memory.

Had another go but reduced the original image to 1381x1381 before importing it.
Much the same, still couldn't extrude.

Any chance of making the point density adjustable?

Mike.