Bulk edit with gradient

[djdstroy]

Hi guys, im trying to edit a number of images all at once.... the images are of faces with plain coloured backgrounds.

i have been using the batch image manipulation tool for bucket fill to change the colours of the image background .... which works great. i can do 100's at once which takes minutes....

but not i want to do the same thing, but using 2 colours and the gradient tool.

i can do this manually one at a time, step by step: 

open the image >
choose the fuzzy select tool >
click and select the background area of the image >
choose the gradient tool >
then with the gradient tool, i will select the x and y points of my gradient on to the image> 

once the gradient has successfully coloured the background i will then click to export the image, and save it as a png file in to my new folder location


sorry if this has been discussed before, 

I have added a before and after example

thanks for your time.