Ask Ubuntu is a question and answer site for Ubuntu users and developers. It's 100% free.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have several hundreds of scanned files as PDFs. The scanner I used at the time creates images that have a blue-grey touch, so the white background of the pages is blue/grey instead of white. While this is not a problem while keeping them on a disk, it is problematic when printing them.

I was wondering whether there is an easy to use tool that I could use to simply optimize the white balance on those files, assuming the background is always perfectly white? I tried using Gimp but that proved quite tedious as I'd have to open each Scan, save the individual pages and then merge them again.

share|improve this question
What you do with gimp you can do commandline too. I found this page:… see if this makes sense to you ;) – Rinzwind Apr 13 '13 at 12:48

convert from imagemagick did the job in my case with commandline:

for file in *.pdf; do convert $file -normalize -level 98%,100% $file.pdf; done

then play with -level parameters in case you are not happy with the result

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.