ofn-erase-background

[Ofnuts]

Try this

• Start Gimp, or close all images (we need to have one single image in Gimp).
  
• Make/load an image with one single layer with something dark over a white background
  
• make sure the layer has an alpha-channel
  
• start the Python console (Filters>Python-fu>Console) and copy these two lines one by one followed by [enter]:
  

Code:

image=gimp.image_list()[0]
pdb.plug_in_colortoalpha(image,image.active_layer,(255,255,255))

Is the white background removed?

PS: when the script ends, have you got a selection? Is it the original one, or has it been shrunk or grown?