Command line tool to correct whitebalance of scanned PDFs

Question

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.

Answer 1

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