Seen September 7th, 2022
Posted April 10th, 2022
1,305 posts
11 Years
Indexing Images
Seeing as many old guides no longer have pictures and some contain outdated methods requiring multiple tools, I felt we were in need of a new tutorial! In short, many images in the third generation of games have a 16-colour limit which is why indexing is required. For the purposes of this tutorial, we're going to index a trainer sprite so that it's ready to be inserted. You'll need an image you want to index and a tool named GraphicsGale which you can download here.


The first thing you'll want to do is open your sprite in GraphicsGale, highlight "All Frames", then hit "Color Depth".

We want to set this to 4bpp as seen above.
When you've done that, you'll notice that your palette has been trimmed down to 16 colours.
Select your entire image at this stage, and hit Ctrl+C to copy. Don't forget to do this!
Even though your image now has a total of 16 colours - technically, your image can only use 15 of those.
Why? The first colour in the palette index will serve as our transparent colour, as per the GBA requirements.

Notice that in the above image our first colour is black; not the green that we want to be our background colour.
How do we fix this? Simply click on the colour, in our case black, drag & drop the values around with our green. We'll end up with this:

Paste/Ctrl+V over it, and boof, it now looks normal again! Sorted.
Export, insert into your ROM, and test.