To create transparent GIFs:
- Create or open an image.
You'll get better results if the areas that you want to cut are aliased.
- Right-click the image, and select Layer > Transparency
> Add Alpha Channel.
GIMP adds the alpha channel without any indication of doing so. The image won't look any different but the alpha channel really is there.
- Select the area you want to make transparent, such as a contiguous
region, a single color, or a hand-drawn region (following figure).
Selected Area in Image
- Cut the selection.
GIMP reveals the underlying alpha channel. The following image shows a white halo effect around the edges that were cut. This is due to aliasing on the original image. You can clean this up by cutting or changing the color of individual pixels.
- Select Image > Mode > Index.
GIF images must use either indexed mode or grayscale mode. If you skip this step now, GIMP will prompt you to export to one of these modes when you save.
- Save the image as a GIF file.
Set the GIF options you want when prompted and click OK. I typically type a short comment about the image.
You now have a transparent GIF.