#!/usr/bin/env bash
# HEADER
#=======================================================================
#
#  img2copie -- Shell script to generate a PDF from a folder of images
#
#  SYNOPSIS
#    img2copie <imagedir>
#
#  DESCRIPTION
#    Shell script to make a PDF file from scanned images of an exam
#    paper isolated in a directory, for example got with "Open Note Scanner.
#    By default, the produced PDF file has the same name as the image
#    folder.
#
#  EXAMPLE
#    $ img2copie <imagedir>
#
#  POSITIONAL ARGUMENT
#    <imagedir>           directory where the image collection is
#
#  OPTIONS
#    -h|--help            display this help and exit
#    -g|--gray            to convert display as grayscale
#    [aA][3-5]            define output page format
#    -m|--mode [screen|ebook|printer|prepress]
#                         ghostscript mode, with image resolution as
#                          - screen: 72 DPI
#                          - ebook: 150 DPI
#                          - printer: 300 DPI
#                          - prepress: 300 DPI
#    -r|--resolution) [num]
#                         compress images with resolution in range
#                         of 72-1200 DPI
#    -f|--flatten         to render transparency to bitmap
#    -o <outputfile>, --output <outputfile>
#                         output PDF file (single)
#
#  EXAMPLES
#    $ img2copie photos/   # will produce photos.pdf
#    $ img2copie photos/ a4 -o copie.pdf
#
#    which is nearly equivalent as:
#    $ img2pdf -o copie.pdf --pagesize a4 photos/*.png
#
#  DEPENDENCIES
#    - ghostscript
#    - imagemagick
#    - GNU coreutils
# 
#  INSTALLATION
#     - copy file to "/home/$(whoami)/bin"
#     - make executable with "chmod +x img2copie"
#     - change permission "none" to "read | write" for PDF in
#       "/etc/ImageMagick-*/policy.xml" such that:
#       <policy domain="coder" rights="read | write" pattern="PDF" /> 
#
#  Copyright (C) 2023 Nicolas Mesnier <nmesnier@free.fr>
#
#  This program is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License version 3 or
#  above as published by the Free Software Foundation.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program. If not, see <http://www.gnu.org/licenses/>.
#
#=======================================================================
# END_OF_HEADER
#-----------------------------------------------------------------------
# *** read this header to display help and version
#-----------------------------------------------------------------------
BOH=$(head -200 ${0} | grep -n "^# HEADER" | cut -f1 -d:)
EOH=$(head -200 ${0} | grep -n "^# END_OF_HEADER" | cut -f1 -d:)
function Help(){
  head -$(($EOH-1)) ${0} | tail -$(($EOH-$BOH-1)) \
    | grep -e "^#$" -e "^# " | sed -e "s/^#=*//g"
}
#=======================================================================
# *** get options ***
#=======================================================================
# default
IMG=""
PDFFILE=""
OPTIONS=""
PDFVERSION="1.4"
MODE="/printer"
RESOLUTION=300
PAPER="a4"

while [[ ${1} ]]; do
    case "${1}" in
        -h|--help) 
            Help
            exit 0 ;;
        -g|--gray)
            OPTIONS+=" -sColorConversionStrategy=Gray"
            OPTIONS+=" -dProcessColorModel=/DeviceGray"
            OPTIONS+=" -dOverrideICC"
            ;;
        -m|--mode)
            case "${2}" in
                screen|ebook|printer|prepress)
                    MODE="/"${2}
                    ;;
                *) echo "Mode must be part of {screen|ebook|printer|prepress}." >&2
                   exit 1;;
            esac
            shift
            ;;
        -r|--resolution)
            if [ ${2} -lt 72 -o ${2} -gt 1200 ];then
                echo "Resolution must be in range 72-1200 DPI." >&2
                exit 1
            else
                RESOLUTION=${2}
            fi
            OPTIONS+=" -dColorImageDownsampleType=/Bicubic" 
            OPTIONS+=" -dColorImageResolution="${RESOLUTION}
            OPTIONS+=" -dGrayImageDownsampleType=/Bicubic" 
            OPTIONS+=" -dGrayImageResolution="${RESOLUTION}
            OPTIONS+=" -dMonoImageDownsampleType=/Bicubic"
            OPTIONS+=" -dMonoImageResolution="${RESOLUTION}
            shift
            ;;
        a3|A3)
            PAPER="a3"        
            ;;
        a4|A4)
            PAPER="a4"
            ;;
        a5|A5)
            PAPER="a5"
            ;;
        -f|--flatten)
            PDFVERSION="1.3"
            ;;
        -o|output)
            if [ -f ${2} ]; then
                read -p " File \"${2}\" allready exists. Replace? y/[n]  " rep
                case ${rep} in
                    [Yy]* )
                        PDFFILE=${2%.pdf}".pdf"
                        ;;
                    * ) exit 1;;
                esac
            else
                PDFFILE=${2%.pdf}".pdf"
            fi
            shift
            ;;
        *)
            if [ -d ${1} ];then
                IMG=${1}
            else
                echo "Directory \"${1}\" does not exists." >&2
                exit 1
            fi
            ;;
    esac
    if ! shift; then
        echo 'Missing parameter argument.' >&2
        exit 1
    fi
done

#-----------------------------------------------------------------------
# *** check if their are images
#-----------------------------------------------------------------------

if [ -z ${IMG} ];then
    echo "You must give a directory for images." >&2
    exit 1
fi

if [ "$(wc -l <(ls -l ${IMG}) | cut -d ' ' -f1)" == 0 ];then
    echo "There must be at leat one image in directory \"${IMG}\"." >&2
    exit 1
fi

#-----------------------------------------------------------------------
# *** output file
#-----------------------------------------------------------------------

# give image directory by default
if [ -z ${PDFFILE} ];then
    PDFFILE=${IMG}".pdf"
fi

if [ -f ${PDFFILE} ]; then
    read -p " File \"${PDFFILE}\" allready exists. Replace? y/[n]  " rep
    case $rep in
        [Yy]* ) ;;
        * ) exit 1;;
    esac
fi

#-----------------------------------------------------------------------
# *** run
#-----------------------------------------------------------------------
# create temp directory and removed it as script exits.
TMPDIR=$(mktemp -d) || exit 1
trap "cd / ; rm -rf '${TMPDIR}'" EXIT

# convert all photos to PDF
for PHOTO in $(find ${IMG}/ -regextype sed -regex ".*/*\.\(jpe\?g\|JPE\?G\|png\|PNG\)" | sort);do
    NEWNAME=$(basename "${PHOTO}" | sed "s/\.\(jpe\?g\|JPE\?G\|png\|PNG\)/.pdf/g")
    convert -background white -page ${PAPER} -compress Zip -quality 0 \
            ${PHOTO} ${TMPDIR}/${NEWNAME}
done

gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -dQUIET \
    -dCompatibilityLevel=${PDFVERSION} -dPDFSETTINGS=${MODE} \
    -dEmbedAllFonts=true -dSubsetFonts=true \
    -dAutoRotatePages=/None ${OPTIONS} \
    -sPAPERSIZE=${PAPER} -dFIXEDMEDIA -dPDFFitPage \
    -sOutputFile=${IMG}.pdf $(ls ${TMPDIR}/*.pdf)

#--------------------------------------------------------------------eof