Crop and convert a bunch PNG into a merged PDF (riping slides from screenshots of zoom call for example)

png2pdfslides.sh

echo "usage: png2pdfslides.sh FOLDER_WITH_PNG CROP_WIDTH by CROP_HEIGHT CROP_OFFSETX CROP_OFFSETX"
echo "output: merged.pdf in FOLDER_WITH_PNG"
echo " "

# This script converts PNG screenshots into a compiled PDF using file name ordering (presumably corresponding to timestamp if consecutive screenshots)
# 1) Goes into folder $MAINF
# 2) Crops an $WIDTH by $HEIGHT region for each PNG starting with a $OFFSETX pixels offset from the left and a OFFSETY pixels offset from the top
# 3) Converts each croped PNG to JPEG2000 for lossless PDF embedding
# 4) Converts each JPEG2000 to PDF
# 5) Merges all the PDFs together into one merged.pdf

MAINF=$1
WIDTH=$2
HEIGHT=$3
OFFSETX=$4
OFFSETY=$5




cd $MAINF


# temporary working folders
mkdir -p crop
mkdir -p jpeg2000
mkdir -p pdfs



# assumes pre-cleaned screenshot where naming convention fits time
# can handle non dense numbering since we never explicitely use counter after initial naming

# init counter
IDX=1


# loop over file using natural timestamp as ordering
# increment $IDX
echo " "
echo "CROPPING"
for f in *.png; 
do 
echo $f; 
convert -crop "$WIDTH"x"$HEIGHT"+"$OFFSETX"+"$OFFSETX" "$f" "crop/crop_"$IDX".png"; 
ls "crop/crop_"$IDX".png"
IDX=$((IDX+1));  
done



# loop over files using normal numbers (no need for leading zeros with -v)
# cut base path
# cut extension
# convert image to jpeg2000
# losslessly imbed jp2 in pdf
echo " "
echo "CONVERTING"
for f in $(ls -v crop); 
do 
s=${f##*/};
s=${s%.png};
convert "crop/$f" -quality 0 "jpeg2000/$s.jp2";
ls "jpeg2000/$s.jp2";
img2pdf -o "pdfs/$s.pdf" "jpeg2000/$s.jp2";
ls "pdfs/$s.pdf";
done



# merge into one pdf with true numerical ordering
echo " "
echo "MERGING"
cd pdfs
pdfunite $(ls -v) ../merged.pdf
cd $MAINF
ls merged.pdf


echo " "
echo "CLEANING PDFs"
rm -r pdfs

echo " "
echo "CLEANING JPEG2000s"
rm -r jpeg2000

echo " "
echo "CLEANING crops"
rm -r crop

The easiest way to figure out the Width, height and offsets is to open one of the screenshot into GIMP, get a rectangle selection that make sense and rip the values, GIMP has the same convention as the convert tool.