Is there any automatic tool to remove edges from an image that has been anti-aliased onto a white background

Question

I have a few images that have been anti-aliased onto a white background that I want to put on a transparent background.

Just selecting it with the -wand tool/fuzzy select tool/select your terminology of choice- and deleting the background tends to leave a ring of off-white pixels around the image, or eat into the image depending on the tolerance setting.

Is there some better way to do this, preferably an automatic tool? (I'm on Linux)

Answer 1

Using Gimp, you can further refine the selection using Select -> Feather. I generally use the wand tool to select the white background, Select -> Grow Selection by 1 pixel, Feather by 2 pixels, and then remove the background.

Answer 2

Have you tried imagemagick? You can specify or change the background color of an image:

mogrify foo.png -background transparent

changes foo in place, while:

convert foo.png -background transparent new.png

doesn't touch foo.png.