That is a good result from denzjos using Hue-Chroma. Unfortunately a GEGL filter and not easily scriptable for your many Images.
IM mogrify -negate is only good for monochrome negatives and you used it on a colour negative. There are IM scripts for conversion see: http://www.fmwconcepts.com/imagemagick/n.../index.php
However this is a Gimp forum and a Gimp process for a colour negative to positive is Colors-> Auto -> White Balance then Colors -> Invert.
How you might get a color-curves file out of your example file (are they all that small ? ) https://youtu.be/uODYcCwryFU duration 4 minutes
..and for a linux BIMP plugin see: https://www.gimp-forum.net/Thread-BIMP-version-2-6
IM mogrify -negate is only good for monochrome negatives and you used it on a colour negative. There are IM scripts for conversion see: http://www.fmwconcepts.com/imagemagick/n.../index.php
However this is a Gimp forum and a Gimp process for a colour negative to positive is Colors-> Auto -> White Balance then Colors -> Invert.
How you might get a color-curves file out of your example file (are they all that small ? ) https://youtu.be/uODYcCwryFU duration 4 minutes
..and for a linux BIMP plugin see: https://www.gimp-forum.net/Thread-BIMP-version-2-6