#!/bin/bash

  # crop parameters (left-right x top-bottom) in [px]
CROP_PARAMS=142x5
  # size reduction
RESIZE_PARAMS=85%
FULL_RES_OUPUT="screenshot-merged-raw.pdf"
REDUCED_OUPUT="screenshot-merged.pdf"

help () { echo "";
  echo "Convert a series of *.png screenshots in the DIR into a merged .pdf."
  echo "via a combination of Iagemagick and img2pdf tools."
  echo "[Ver. 1.0, 2020-06-20 by ILC]"; 
  echo "----------------------------------------------"
  echo "Usage (short): screenshot2pdf DIR/"
  echo "Usage (full):  screenshot2pdf CROP RESIZE DIR/"
  echo "Example:       screenshot2pdf 142x5 85% ./"
  echo "----------------------------------------------"
  echo "This will produce a 'screenshot-merged.pdf' in the DIR/."
  echo "Default CROP (left/right x top/bottom) in [px] = 142x5"
  echo "Default RESIZE = 85%"
  echo "See Imagemagick 'convert' manual for more details."; echo ""
}
if [[ $# -eq 0 ]]; then help; exit; fi
  # read working dir, removing a possible trailing "/", and other params
if [[ $# -eq 3 ]]; then
  CROP_PARAMS=$1; RESIZE_PARAMS=$2; WORKING_DIR="${3%/}";
elif [[ $# -eq 1 ]]; then
  WORKING_DIR="${1%/}";
else
  echo "Incorrect number of arguments!"; help; exit 2
fi
TEMP_DIR="$WORKING_DIR/temp_images_$RANDOM"
  # create a temp directory for conversion
mkdir $WORKING_DIR/$TEMP_DIR
mkdir $WORKING_DIR/$TEMP_DIR/reduced
  # trim and downsample all PNGs in the current directory
i=1; 
echo "Processing '$(realpath $WORKING_DIR)/*.png'"; echo "with 'convert -shave $CROP_PARAMS -resize $RESIZE_PARAMS'"
for filename in $WORKING_DIR/*.png; do
  new_filename=$(printf "%02d" $i)
  convert -shave $CROP_PARAMS "$filename" $TEMP_DIR/${new_filename}.png;
  convert -shave $CROP_PARAMS -resize $RESIZE_PARAMS +repage "$filename" $TEMP_DIR/reduced/${new_filename}.png;
  i=$((i+1)); 
  printf "$new_filename "
done

  # create a batched pdf
printf "Done. \nConverting into pdf... "
img2pdf --output $WORKING_DIR/$FULL_RES_OUPUT $TEMP_DIR/*.png
img2pdf --output $WORKING_DIR/$REDUCED_OUPUT $TEMP_DIR/reduced/*.png

printf "Done.\n"

rm -r $TEMP_DIR