creates a shadow (transparent) version of the image
i use this script for colorizing an img with CSS/HTML
i.e. I display the shadow img (in the HTML) and change the bg color with CSS
if u use the original colors from the picture u should get almost the same picture
u can play with the black-point/white-point values for less/more gray...
though it doesn't change much...
it meant to be use with uni-color img, but works with any img.
tested on png, jpg, GIMP 2.6.6
it gives an error message: Error: illegal function
I dont know why (didn't had the energy to debug it) but it works fine for me any way
so I simply ignore it
see GIMP on-line help for installation instruction of script-fu
usage: open an image and run the script
Note: i test it only on a flat image,
with multiple layer it should operate on the current active layer
after running the script:
* delete invisible layer (optional)
* merge visible layer (optional)
* save with a different name (as png for keeping the transparent charecteristic of the image)