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@diramazioni
Created September 15, 2013 18:17
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A script I quickly come up for my needs to extract image from pdf, preprocess and extract text with tesseract
#!/bin/bash
STARTPAGE=2
ENDPAGE=75
SOURCE=book.pdf
OUTPUT=book.txt
RESOLUTION=600
LAYOUT="1"
[[ -e out.txt ]] && rm out.txt
for i in `seq $STARTPAGE $ENDPAGE`; do
echo processing page $i
[[ ! -e page_"$i".png ]] && convert -colorspace Gray -crop 6704x5408+1894+0 -density $RESOLUTION $SOURCE\[$(($i - 1 ))\] page_"$i".png
if [[ ! -e 8/page8_$i.png ]]; then
convert -depth 8 -brightness-contrast +30x+100 page_"$i".png 8/page8_$i.png # need to convert to 8 color bit in order to make unpaper work
fi
if [[ ! -e pages/page_"$i"_1.png || ! -e pages/page_"$i"_2.png ]]; then
echo "**** unpaper $i"
rm page_"$i".pnm page_"$i"_1.pnm page_"$i"_2.pnm page_"$i"_1u.pnm page_"$i"_2u.pnm 2>/dev/null
if [[ LAYOUT == "1" ]]; then
convert -crop 3352x5408+1894+0 8/page8_"$i".png 8/page8_"$i"_1.png
convert -crop 3352x5408+5246+0 8/page8_"$i".png 8/page8_"$i"_2.png
pngtopnm 8/page8_"$i"_1.png >page_"$i"_1.pnm
pngtopnm 8/page8_"$i"_2.png >page_"$i"_2.pnm
unpaper --layout single -dn left -ds 1500 -dd 0.6 -dv 1.1 page_"$i"_1.pnm page_"$i"_1u.pnm
unpaper --layout single -dn right -ds 1500 -dd 0.6 -dv 1.1 page_"$i"_2.pnm page_"$i"_2u.pnm
else:
pngtopnm 8/page8_$i.png >page_"$i".pnm
unpaper --layout double --output-pages 2 -dn left -ds 1500 -dd 0.6 -dv 1.1 -mw 350 page_"$i".pnm page_"$i"_%d.pnm
fi
convert page_"$i"_1u.pnm pages/page_"$i"_1.png
convert page_"$i"_2u.pnm pages/page_"$i"_2.png
fi
tesseract pages/page_"$i"_1.png out -l deu
echo "--------------------------------- pdf $i A ---------------------------------">> $OUTPUT
cat out.txt >> $OUTPUT
tesseract pages/page_"$i"_2.png out -l deu
echo "--------------------------------- pdf $i B ---------------------------------">> $OUTPUT
cat out.txt >> $OUTPUT
done
@diramazioni
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The different value for LAYOUT control the mode unpaper works with double layout performs the deskew comparing left and right side. I've tried both ways with mixed results, seems that --deskew-scan-size plays a big role in fixing incorrectly rotated images, test out what works best for your scanned pages.

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