spectrscan/spectrscan

#!/usr/bin/env bash

#
# spectrscan
#
# Copyright (C) 2017-2018 frnmst (Franco Masotti) <franco.masotti@live.com>
#                                                 <franco.masotti@student.unife.it>
#
# This file is part of spectrscan.
#
# spectrscan is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# spectrscan 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 spectrscan.  If not, see <http://www.gnu.org/licenses/>.
#

. ./spectrscan.conf

check_software()
{
    which \
        scanimage \
        unpaper \
        awk \
        convert \
        pdftk \
        parallel \
        file \
        pamfix
}

get_last_page_side_a()
{
    ls spectrscan_out*.pnm | sort --reverse | head -n1 | tr -d [a-z]._
}

select_page_parameters()
{
    if [ "${two_sided}" = 'true' ] && [ "${side_b}" = 'true' ]; then
        # side_b
        batch_start=$(("$(get_last_page_side_a)"+1))
        batch_increment=-2
    elif [ "${two_sided}" = 'reverse' ] && [ "${side_b}" = 'true' ]; then
        # side_b
        batch_start=2
        batch_increment=2
    fi
    if [ "${two_sided}" != 'false' ] && [ "${side_a}" = 'true' ]; then
        # true, reverse; first side.
        batch_start=1
        batch_increment=2
    fi
    if [ "${two_sided}" = 'false' ]; then
        # single sided
        batch_start=1
        batch_increment=1
    fi
}

build_scan_sub_command()
{
    # Since these are scanner specific options, they need to be probed.
    #
    # Put source option before resolution to avoid the error:
    # https://bugs.launchpad.net/simple-scan/+bug/983441
    local scan_command=''
    [ -n "$(get_supported_resolutions)" ] && scan_command=""${scan_command}" --source "${source}""
    [ -n "$(get_supported_modes)" ] && scan_command=""${scan_command}" --resolution "${resolution}""
    [ -n "$(get_supported_sources)" ] && scan_command=""${scan_command}" --mode "${mode}""

    echo "${scan_command}"
}

scan()
{
    select_page_parameters
    local scan_sub_command="$(build_scan_sub_command)"

    scanimage \
        ${scan_sub_command} \
        --batch=spectrscan_out%08d.pnm \
        --batch-start ${batch_start} \
        --batch-increment ${batch_increment} \
        --progress \
        --format=pnm
}

exists_output_file()
{
    # Check if output file exists and is a pdf file.
    # This is needed to concatenate new documents to an
    # already existing pdf file.
    if [ -f "$SRC_DIR"/"$output_file" ]; then
        if [ "$(file --mime-type "$SRC_DIR"/"$output_file" \
            | awk '{ print $2 }')" = "application/pdf" ]; then
            echo 'true'
        else
            # Not a pdf file.
            echo 'error'
        fi
    else
        echo 'false'
    fi
}

convert_single()
{
    # First convert to pdf with the image enhancements, then apply unpaper.
    # This gives better results because it avoids missing information
    # removed by unpaper in the final result.
    local filE="${1}"

    pamfix -truncate "$filE" > "$filE".tmp.pnm.bis

    if [ "${imagemagick_options}" != 'false' ]; then
        convert ${imagemagick_options} "$filE".tmp.pnm.bis "$filE".tmp.pnm
    else
        mv "$filE".tmp.pnm.bis "$filE".tmp.pnm
    fi

    if [ "${unpaper_options}" = 'true' ]; then
        unpaper --overwrite -q "$filE".tmp.pnm "$filE".pnm
    elif [ "${unpaper_options}" = 'false' ]; then
        mv "$filE".tmp.pnm "$filE".pnm
    else
        unpaper --overwrite -q ${unpaper_options} "$filE".tmp.pnm "$filE".pnm
    fi

    #
    # OCR stuff goes here.
    #

    convert -compress lzw "$filE".pnm "$filE".pdf

} 1>/dev/null 2>/dev/null

# TODO use inotify || add option to post process if not available
# (eg: sshfs filesystem).
# process in /tmp if possible. -> the previous check is not needed.
pnm_to_pdf()
{
    # A hack to avoid GNU Parallel's message
    mkdir -p ~/.parallel && touch ~/.parallel/will-cite
    # n = number of new pages
    # Time complexity: O(n/#threads)
    export -f convert_single
    export unpaper_options
    export imagemagick_options
    parallel --bar convert_single ::: "$(ls spectrscan_*.pnm)"
}

pdf_cat()
{
    printf "%s\n" 'assembling PDF...'
    # O(n)
    # Always cat to the output file.
    # Unlike pdfunite, pdftk does not corrupt the pdf.
    pdftk *.pdf cat output "$output_file".tmp

    # O(1)
    if [ "$(exists_output_file)" = 'true' ]; then
        cp "$SRC_DIR"/"$output_file" "$SRC_DIR"/."$output_file"
        pdftk "$SRC_DIR"/."$output_file" "$output_file".tmp \
            cat output "$SRC_DIR"/"$output_file"
        rm "$SRC_DIR"/."$output_file"
    elif [ "$(exists_output_file)" = 'false' ]; then
        mv "$output_file".tmp "$SRC_DIR"/"$output_file"
    else
        printf "[ERROR]\n" 1>&2-
        exit 1
    fi
}

get_supported_parameters()
{
    scanimage -A | grep -e '--source' -e '--mode' -e '--resolution'
}

get_supported_resolutions()
{
    echo "${supported_params}" | grep resolution | awk '{print $2}' | tr '|' ' ' | tr -d 'dpi'
}

get_supported_modes()
{
    echo "${supported_params}" | grep mode | awk '{print $2}' | tr '|' ' '
}

get_supported_sources()
{
    echo "${supported_params}" | grep source | awk '{print $2}' | tr '|' ' '
}

chain()
{
    mkdir "${TMP_DIR}"
    pushd "${TMP_DIR}"

    if [ "${two_sided}" != 'false' ]; then
        side_a='true'
        scan \
            && printf "%s\n" 'turn the paper(s) and hit return when ready' \
            && read \
            && side_a='false'; side_b='true' \
            && scan
    else
        scan
    fi

    pnm_to_pdf
    pdf_cat

    popd
    rm -rf "${TMP_DIR}"
}

preliminary_checks()
{
    # Leak all variables to avoid passing them every time.
    imagemagick_options="${1}"
    mode="${2}"
    resolution="${3}"
    source="${4}"
    unpaper_options="${5}"
    two_sided="${6}"
    output_file="${7}"

    # Get the parameters and check that the scanner is connected.
    supported_params="$(get_supported_parameters)"
    # FIXME: this might not work.
    local retval=${?}
    [ ${retval} -ne 0 ] && return ${retval}
    chain
}

check_software || exit ${?}
. ./fbopt