#! /usr/bin/env bash

# =======================================================================================
# This is part of the How-To article submitted to TranslatorsCafe.com by Daniel Storbeck
# http://www.translatorscafe.com/cafe/Articles.asp?ArtID=109
# =======================================================================================

# convert one PDF document to a set of JPEG images
# each representing one page of the source document

# check syntax of given command line
if [ $# -ne 1 ]
then
    printf "%b" "Error. The script takes exactly one argument.\n" >&2
    printf "%b" "usage: transform file.pdf\n" >&2
    exit 1
fi

# get file name without extension
# assume the file name doesn't contain any whitespace
FNAME=${1%.[pP][dD][fF]}
if [ -z $FNAME ]
then
    printf "%b" "Error. Cannot process the given file name.\n" >&2
    printf "%b" "usage: transform file.pdf\n" >&2
    exit 1
fi

# get the number of pages in the PDF document
# to do this we need the pdfinfo, grep and awk commands
NRPAGES=$(pdfinfo $1 | grep "Pages:" | awk '{print $2}')

# get number of digits of number of pages
DIGITS=0
NUMBER=$NRPAGES
while [ $NUMBER -gt 0 ]
do
    NUMBER=$(($NUMBER/10))
    DIGITS=$(($DIGITS+1))
done

# convert from PDF to PS
pdftops $1

# split the PS document in individual pages
NRPAGESPLUSONE=$(($NRPAGES+1))
for (( N=1 ; N<$NRPAGESPLUSONE ; N++ ))
do
    # get number of digits of actual number
    DGTS=0
    NUMBER=$N
    while [ $NUMBER -gt 0 ]
    do
	NUMBER=$(($NUMBER/10))
	DGTS=$(($DGTS+1))
    done
    # get number of zeros in prefix
    NRZEROS=$(($DIGITS-$DGTS))
    # do the padding
    NRPADDED=$N
    while [ $NRZEROS -gt 0 ]
    do
	NRPADDED="0"$NRPADDED
	NRZEROS=$(($NRZEROS-1))
    done
    # extract actual page
    echo -n "psselect: "
    psselect -p$N $FNAME.ps $FNAME$NRPADDED.ps
    # convert to JPEG
    convert -density 300 $FNAME$NRPADDED.ps $FNAME$NRPADDED.jpg
    echo "converted page nr. $N to JPEG"
    # delete PS page
    rm $FNAME$NRPADDED.ps
done

# remove the PS document
rm $FNAME.ps