A quick script to automate the background erasure when the background is uniform.
- Make a selection on the background using the fuzzy selector with a threshold big enough to include small irregularities
- Use Layer>Erase background
- Most of the background is completely deleted and is guaranteed to be totally transparent (thanks Blighty)
- The color used for color-to-alpha is deduced from the erase background color, and so doesn't ned to be specified.