Transparency Tutorial (GIMP)
Welcome to the Transparency Guide for the GIMP! Let's get started.Saving and Opening a Picture
First, let's get the image you want to transparatize. Let's save this Gold Version Mareep sprite from Veekun. (Thanks to Eevee)
Once the picture is saved to your hard drive, open it in GIMP by clicking on File>>Open or Ctrl+O. Now zoom in to 800% (the Zoom is located on the bottom-left toolbar).
This is how it should look.
Adding an Alpha Channel
Next, we add the alpha layer. An Alpha Channel (also called Alpha Layer) is a transparent layer under your image. First, right-click the image, and click Layers>>Transparency>>Add Alpha Channel. This adds the Alpha Channel under your image. If you are unable to click it, the image already contains an Alpha Channel.How to add an Alpha Channel.
Trimming the Picture
The next step is to remove all the white parts that are not part of the picture. To do this, select the Magic Wand Tool.
Under the Magic Wand Tool menu, set the Threshold to about 15.0.
Now click on the white area of the picture. It should be surrounded by a line of "marching ants". Now press Delete. The white should disappear, and a checkerboard background should show up in its place. The checkerboard background represents transparency.
Checkerboard Background
You'll notice there is still some white left between the tail and the body; you need to delete that as well, along with any other white you see that isn't part of the sprite itself.
After all the white is gone, just save as
.png and you're done!