So I was messing around working on a sprite for my own code.
and I was foolish enough to name my East facing sprites E1, E2, E3 etc.
This was not liked when I imported them into the .dmi
Essentially, Upon importing these E# sprites into an icon_state (a movie not a pixmap, if it matters) They tweened and became about 3x smaller than they were when I made them, checking the original files this 3x smaller version was not present. I confirmed it was just E# because I changed many other sprites I had to follow the E1,E2,E3 pattern, and sure enough, upon importing, they were 3x smaller and tweened.
This annoyed me because I couldn't use my East facing sprites, so I tried importing them into the .dmi, not into an icon_state within the .dmi and this is the result:
Weird right?
It works with all images named E1,E2,E3 etc.
My suspicion is that it has something to do with how byond saves .dmi's internally, Looking at a .dmi on a windows machine when the file is on a desktop, you can see each state of the icon_state individually, because they're saved in the image's metadata. I suspect this due to how importing an image larger than 32x32 into a 32x32 sized .dmi chopped it up into 32x32 sized chunks.
So yeah, if you need to save sub images of an animated state that faces East, do not named it E1,E2 etc.