Scan and/or convert

scan

#!/bin/bash -eu

: ${SCANNER:="brother4:bus9;dev1"} # My USB scanner
: ${OCR_LANG:=nld}                 # Tesseract language
: ${SCAN_DPI:=300}                 # A good resolution for OCR
: ${FINAL_RES:=1240x}              # A good resolution for PDF
: ${SHOW:=0}                       # Show the result
: ${NICE:=10}                      # Priority of this process - this prevents Tesseract from hogging your machine
: ${UNPAPER:=1}                    # Whether to run unpaper
: ${FILENAME:=AUTO}                # If no FILENAME is set, or set to 'AUTO': make one up based on time
: ${VERBOSE:=0}                    # Whether to print verbose information

: ${ROOT_DIR:=$PWD}
: ${INPUT_DIR:=${ROOT_DIR}/input}
: ${INTER_DIR:=${ROOT_DIR}/inter}
: ${OUTPUT_DIR:=${ROOT_DIR}/output}

red=$(tput setaf 1)
green=$(tput setaf 2)
blue=$(tput setaf 4)
reset=$(tput sgr0)

function usage() {
    cat <<EOF
Usage: $0 subcommand

Subcommands:

- scan: scan documents into '${INPUT_DIR}' folders
- convert: convert previously scanned documents into '${OUTPUT_DIR}' folders

EOF
}

function echo_verbose() {
    if [[ "$VERBOSE" == "1" ]]; then
        echo "$@"
    fi
}

function timed_dir() {
    date "+%F_%T" | sed 's/:/-/g' # Don't use ':' because of Windows
}

function _scan() {
    PAGE=1
    SCAN_SUB_DIR=$(timed_dir)

    while true; do
        cat <<EOF

Press:
  [enter] to scan,
  [n] for new document,
  [l] to scan the last page, then start new document,
  [ctrl+c] to abort

Going to scan page '${red}${PAGE}${reset}' into '${green}${SCAN_SUB_DIR}${reset}'
EOF
        read ACTION

        case "${ACTION}" in
        n)
            finish_scan "${SCAN_SUB_DIR}"

            PAGE=0
            SCAN_SUB_DIR=$(timed_dir)
            ;;
        l)
            scan_file "${SCAN_SUB_DIR}" "${PAGE}"
            finish_scan "${SCAN_SUB_DIR}"

            PAGE=0
            SCAN_SUB_DIR=$(timed_dir)
            ;;
        *)
            scan_file "${SCAN_SUB_DIR}" "${PAGE}"
            ;;

        esac

        PAGE=$((PAGE + 1))
        echo
    done
}

function finish_scan() {
    SCAN_SUB_DIR="$1"
    FULL_DIR="${INPUT_DIR}/${SCAN_SUB_DIR}"

    if [[ -d "${FULL_DIR}" ]]; then
        cat <<EOF >>"${FULL_DIR}/info"
SCAN_DPI='${SCAN_DPI}'
OCR_LANG='${OCR_LANG}'
FINAL_RES='${FINAL_RES}'
UNPAPER='${UNPAPER}'
EOF
        touch "${FULL_DIR}/done"
    fi

    echo
    echo "==================================================================================="
}

function scan_file() {
    SCAN_SUB_DIR="$1"
    PAGE="$2"
    FULL_DIR="${INPUT_DIR}/${SCAN_SUB_DIR}"
    FILE="${FULL_DIR}/page_$(printf "%03d" "${PAGE}").tiff"

    echo "Now scanning page '${red}${PAGE}${reset}' into '${green}${FULL_DIR}${reset}'"
    mkdir -p "${FULL_DIR}"
    touch "${FULL_DIR}/info"

    scanimage -p -d "${SCANNER}" \
        --format=tiff \
        --resolution "${SCAN_DPI}" \
        --output-file "${FILE}"

    echo "Finished."
}

function _convert() {
    mkdir -p "${OUTPUT_DIR}"

    for entry in ${INPUT_DIR}/*; do
        [[ ! -d "${entry}" ]] && continue
        [[ ! -f "${entry}/done" ]] && continue

        convert_dir "${entry}"
        rm -rf "${entry}"
    done
}

function convert_dir() {
    inputdir="$1"

    subdir=${inputdir#${INPUT_DIR}/}
    interdir="${INTER_DIR}/${subdir}"

    UNPAPER=1
    FILENAME="${OUTPUT_DIR}/${subdir}.pdf"

    if [[ -f "${FILENAME}" ]]; then
        echo_verbose "Already processed '${red}${inputdir}${reset}' - ${blue}skipping${reset}!"
        return
    fi
    echo "Converting: '${red}${inputdir}${reset}' into '${green}${interdir}${reset}'"

    [[ -f "${entry}/info" ]] && source "${entry}/info"

    mkdir -p "${interdir}"

    COMBINED_TIFF="${interdir}/combined.tiff"
    if [[ "${UNPAPER}" == "1" ]]; then
        pre_process "${inputdir}" "${interdir}"
        convert "${interdir}"/page_*-unpaper.pnm "${COMBINED_TIFF}"
    else
        convert "${inputdir}"/page_*.tiff "${COMBINED_TIFF}"
    fi

    echo_verbose "Rescaling output PDF..."
    convert "${COMBINED_TIFF}" -scale "${FINAL_RES}" -compress jpeg -quality 75 "${interdir}/combined.pdf"

    echo_verbose "Running OCR..."
    tesseract -l "${OCR_LANG}" -c textonly_pdf=1 "${COMBINED_TIFF}" "${interdir}/ocr" pdf

    qpdf "${interdir}/combined.pdf" --underlay "${interdir}/ocr.pdf" -- "${FILENAME}"

    echo "Conversion of '${FILENAME}' is done"

    rm -rf "${interdir}"
}

function pre_process() {
    INPUT="$1"
    OUTPUT="$2"
    PAGES="${INPUT}"/page_*.tiff
    COUNT=$(find "${INPUT}" -name 'page_*.tiff' | wc -l)

    echo "Pre-processing ${red}${COUNT}${reset} page(s) in parallel..."

    for PAGE in $PAGES; do
        name="$(basename "$PAGE")"
        outputname="${name%.tiff}-unpaper.pnm"
        pre_process_page "${PAGE}" "${OUTPUT}/${outputname}" &
    done | parallel --bar -u

}
function pre_process_page() {
    INPUT="$1"
    OUTPUT="$2"

    echo "unpaper --overwrite -q --dpi 300.0 '${INPUT}' '${OUTPUT}' 2>/dev/null"
}

function test_deps() {
    deps=""
    case "$1" in
    scan)
        deps="scanimage"
        ;;
    convert)
        deps="unpaper convert tesseract qpdf parallel"
        ;;
    esac

    for command in ${deps}; do
        if ! command -v "${command}" &>/dev/null; then
            echo "Missing command: '${command}'"
            command "${command}"
            exit 1
        fi
    done
}

function _run() {
    COMMAND="$1"

    test_deps "${COMMAND}"

    case "${COMMAND}" in
    scan) _scan ;;
    convert) _convert ;;

    h | help) usage && exit 0 ;;
    *) usage && exit 1 ;;
    esac

}

_run ${1:-help}