dwim-ocr.sh - ocr a pdf document to current directory as mono bitmap

dwim-ocr.sh

#!/bin/bash
# dwim-ocr.sh - ocr a pdf document to current directory as mono bitmap
# created by scruss on Fri 11 May 2012 19:56:03 EDT
# $Id: dwim-ocr.sh,v 1.5 2017/03/28 20:58:39 scruss Exp $

set -eu
input="$1"
# uses $2 if specified, sensible default otherwise
output=${2:-${1%\.*}-ocr.pdf}
# but check that the output isn't a bare file or pdfbeads will choke
if
    [ "$output" == "$(basename "$output")" ]
then
    output="${PWD}/$output"
fi
echo "Writing to ${output} ..."
tmpdir="$(mktemp -d /tmp/dwim-ocr.XXXXXXX)" || exit 1

# extract images of the pages (note: resolution hard-coded)
# FIXME at some point; use pdftoppm?
gs -SDEVICE=tiffg4 -r360x360 -sOutputFile="$tmpdir/page-%04d.tif" -dNOPAUSE -dBATCH -- "$input"

# OCR each page in parallel and convert into PDF
pushd "$tmpdir"
ls -1 page-*.tif | parallel --no-notice --gnu tesseract {} {.} hocr

# combine the pages into one PDF
pdfbeads -o "$output" *

popd
rm -rf -- "$tmpdir"

# check if job failed
if
    [ ! -s "$output" ]
then
    rm -f "$output"
    echo "$output" failed.
    exit 1
fi