====== Tools: unpaper ======

Recently I wanted to print a few scanned pages. However, due to the low quality of the source material (see below) reducing the pages to black&white didn't exactly improve them.

Enter [[http://unpaper.berlios.de/|unpaper]]. 
While unpaper is a rather unknown tool it's also extremely useful
because it allows diverse image modifications to improve scanned pages, e.g.:

  * black-/gray-/noise-/blurfiltering
  * deskewing
  * border-aligning
  * mask-centering
  * etc.

If you aren't sold yet the [[http://unpaper.berlios.de/unpaper.html|documentation]] offers other great examples of applied image processing techniques.

{{ :blog:2008:06:unprint.png |}}

Below I've included the minimal((''meaning: quick&dirty'')) script I used to process the scanned pages. While the settings produced sufficient results for my needs they are probably still far from perfect -- so don't forget to toy with your settings to get optimal results ,)

<code bash|autounpaper>
#!/bin/bash
# Usage: autounpaper *.jpg

inputfiles=$*
tmpin=`mktemp -t autounpaper-in-XXXXXXXXXX`.pgm
tmpout=`mktemp -t autounpaper-out-XXXXXXXXXX`.pgm

opts="-q --overwrite"
opts+=" --no-deskew --no-mask-scan"
opts+=" --grayfilter-size 1,1 --grayfilter-step 1,1 --grayfilter-threshold 0.4"

echo -n "Processing:"

for input in $inputfiles; do
	echo -n " $input"
	ending=${input#*.}
	output=${input%.*}-unpaper.$ending

	convert $input $tmpin && echo -n . && \
	unpaper $opts $tmpin $tmpout && echo -n . && \
	convert $tmpout $output
done

rm $tmpin $tmpout

echo
</code>

{{tag>sh quick_and_dirty tools}}

~~DISCUSSION~~