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!