For linux users.Molly raised the subject of this little utility, 'ChangeImage'.
http://registry.gimp.org/node/25571 It is a standalone windows application and not a Gimp script/plugin but it does make nice Gimp .ggr gradients.
A very quick demo of calling this from Gimp using RobA's Shellout script.
http://youtu.be/AfWVoYBmIokcaveats:
This is 32 bit linux - PClinuxOS
I never managed to get Shellout greater than ver 0.5 to work in linux
Using WINE ver 1.4 , I found the latest ver 1.6 breaks several of my win utilities so I reverted back.
note on youtube
If you can not hear any audio and/or the video is very small, not my fault, it is youtube flash settings
adjust the youtube player