Only a single program was used to safely compress all textures in MTG.
* `optipng -o7 -zm1-9 -nc -strip all -clobber %%f`
The key command used is -nc, which stops color mode changes. I.e. any RGBA textures will remain RGBA textures, with none being changes to 8-bit indexed mode.
utils/optimize_textures.sh performs this compression automatically, assuming optipng is installed.
This keeps the filenames the same, but adds a new "inside" double texture
for the open chest.
Use regular drawtype for closed chest and delete the "cube.obj" model.
X-flip the right-side texture for the closed chest.