How to create a color palette to share with several graphics (views, animations) using GIMP

Based on GIMP 2.18 and the plugin BIMP 1.17 (previous versions had bugs). GIMP is a free commonly used graphic editor, BIMP is a plugin to perform batch operations.

GIMP

Preparation

• Create new image
• Drag and drop all .PNGs of the animal on the new image canvas (or better: do these steps separately for male, female if different than male, young and icons). After GIMP has added each image as a new layer, you should see the total amount of your .PNGs + 1 (empty layer).
• Hint: you can recover an additional color by removing the empty layer.

Creating the color palette

• Go to menu Image -> Mode -> Indexed.
• A dialog window opens. Choose Color Palette and pick Generate Optimum Palette . Assuming you rendered images with for example Blender or whatever, your background is not transparent, but it's a color (eg flashy green) which you'll want to turn into a transparent color at a later point. If this is the case, simply create a color palette of 256 colors.

Using the color palette

• You should now find a toolwindow named Palettes. It should contain something like Colormap of Image #1 (untitled) .
• Right click to rename and/or save.

Batch process PNGs

• We are using a free GIMP plugin called BIMP (Batch Image Manipulation).
• Add the folder containing only the graphics you're preparing (make sure to check it adds everything within that folder)
• Add a manipulation (action): gimp-image-convert-indexed , choose CUSTOM_PALETTE and at the bottom specify the name of the color palette you've created/renamed/saved earlier
• be careful to set your Output Folder correctly. You do need to specify it explicitly! (not very intuitive)
• hit Apply

Hint: set your background color in ZT Studio to the same one you're using in your images to be able to use the 255 (+1 transparent) color as intended!

Final note: if you are planning to simply use the generated GIMP Color Palette (.GPL) as the actual file / color palette to be used in the batch conversion feature of ZT Studio, you should make sure the background color (e.g. flashy green, the color you DON'T want to see in ZT1) is the first color in this palette!