i've written a small tool for windows for the AGK App Jam
that may be useful to you where you can load an image, Define
SubImages and Save as subimages.txt
each as an Animation, Slice
SubImages as their own .png files or Dice
each tile or frame of a given SubImage similarly.
an image with an already-defined subimages.txt file can also be loaded in and further Edited
with the existing SubImage data pre-populated.
visit my itch.io page HERE
to see the short .gif demo
and download the zip which includes a User Guide to get you started.
i hope that you find it useful and appreciate any feedback with it in the mind that it's to be a "light" development tool with room for expansion in functionality. while i have some additional features in mind, any suggestions are appreciated.