Brighten and unify the background of a scanned image

Question

My girlfriend has scanned a few comics images, drawn with pencil. She wants to publish them on the web, but the different grayscale shadows of the paper are still evident in the image.

I would like to make all the light gray colors transferred into while background, using a simple method and open source software.

Any ideas?

Udi

Answer 1

Using ImageMagick you can achieve it like this:

convert source.jpeg -white-threshold 75% target.jpeg

All pixels in the source image with a brightness level of 75% or higher will be set to white in the target image. Just play with the threshold value until you get something that works well. It could be a problem if parts of the drawing comes out brighter than the paper in your scans, but that shouldn't normally be the case.