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kbauer/imagemagick-scan-to-mono.sh

Last active May 31, 2021 17:26
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  1. kbauer revised this gist Aug 19, 2015. No changes.
  2. kbauer created this gist Aug 19, 2015.
    62 changes: 62 additions & 0 deletions imagemagick-scan-to-mono.sh
    View file
    Original file line number Diff line number Diff line change
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    #!/usr/bin/env bash
    # -*- mode: sh; coding: us-ascii-unix -*-

    source libstacktrace || true
    set -e -u -E

    MANUAL="
    Usage: $0 INFILE OUTFILE [BLURRADIUS;default:20px]
    Takes a document scan INFILE (an image) and produces a monochromatized
    output file version.
    If INFILE=OUTFILE, creates a backup file INFILE.000.bak etc.
    If Only INFILE is given, uses BLURRADIUS=0 and OUTFILE=INFILE, which
    is useful when editing a mono-chromed file has inflated its file size.
    Note that OUTFILE will always be a PNG file, regardless of extension.
    The method for removing the background brightness gradient is based on
    the discussion
    http://superuser.com/questions/693339/
    "

    if [[ "${1:-}" = "-?" ]] || [[ "${1:-}" = "-h" ]] || \
    [[ "${1:-}" = "--help" ]] || [[ $# -lt 1 ]]; then
    echo "$MANUAL"
    exit 0
    fi

    INFILE="$(readlink -m "$1")"
    if [[ $# -gt 1 ]]; then
    BLURRADIUS="${3:-20}"
    OUTFILE="$(readlink -m "$2")"
    else
    BLURRADIUS=0
    OUTFILE="$INFILE"
    fi
    TMPDIR="$(mktemp -d)"
    cd "$TMPDIR"

    if [[ $INFILE = $OUTFILE ]]; then
    bakname() { printf "$INFILE.%03d.bak" "$1"; }
    i=0;
    while [[ -e $(bakname $i) ]]; do i=$((i+1)); done
    BAKNAME=$(bakname "$i")
    cp "$INFILE" "$BAKNAME"
    fi
    if [[ $BLURRADIUS -ne 0 ]]; then
    convert -density 150 "$INFILE" -background white -flatten -colorspace Gray 01.png
    convert 01.png -blur "${BLURRADIUS}x${BLURRADIUS}" 02.tif
    convert 01.png 02.tif -compose Divide_Src -composite 03.tif
    convert 03.tif -threshold 80% -type bilevel -compress group4 png:"$OUTFILE"
    else
    convert "$INFILE" -threshold 80% -type bilevel -compress group4 png:"$OUTFILE"
    fi

    rm -f 01.png 02.tif 03.tif
    rmdir "$TMPDIR"