OCR multipage pdf file

ocr-multipage-pdf.sh

#!/bin/bash

#
# Optical character recognition for multipage pdf file
#
#
# Prerequisites:
# pdftk, cuneiform, imagemagick
#

#
# Disclaimer
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
# INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND  FITNESS FOR A PARTICULAR PURPOSE ARE 
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE 
# USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
# 

tempDirectory="tmp-"`date +%s`
defaultLanguage="rus"

pagesDirectory="pages"
imagesDirectory="pages-images"
textDirectory="text"
startProcessingMessage="Start processing"
endProcessingMessage="OK"
DELIMITER="---"

function get_working_directory_path() {
    echo "/tmp/$tempDirectory"
}

function get_pages_directory_path() {
    echo "`get_working_directory_path`/$pagesDirectory"
}

function get_images_directory_path() {
    echo "`get_working_directory_path`/$imagesDirectory"
}

function get_text_directory_path() {
    echo "`get_working_directory_path`/$textDirectory"
}

function get_default_language() {
    echo $defaultLanguage
}

function create_directory() {
	path=$1
	echo "creating directory \"$path\""
        echo "mkdir $path"
	mkdir $path
}

function remove_directory() {
	path=$1
	echo "removing directory \"$path\""
	echo "rm -rf $path"
	rm -rf $path
}

function split_multipage_pdf_to_separate_pages() {
    inputFile=$1
    pagesDirectory=$2
    echo "splitting $inputFile to separate pages"
    echo "pdftk $inputFile burst output $pagesDirectory/page_%04d.pdf"
    pdftk $inputFile burst output $pagesDirectory/page_%04d.pdf
}

function generate_images_for_all_pages() {
    pagesDirectory=$1
    imagesDirectory=$2
    for page in $(eval "echo ${pagesDirectory}/*.pdf")
    do
	echo "convert -density 300 $page $imagesDirectory/`basename $page`.png"
	convert -density 300 $page $imagesDirectory/`basename $page`.png
    done
}

function ocr_images() {
    imagesDirectory=$1
    textDirectory=$2
    language=$3
    for image in $(eval "echo ${imagesDirectory}/*.png")
    do
	echo "cuneiform -l rus -o $textDirectory/`basename $image`.txt $image"
	cuneiform -l rus -o $textDirectory/`basename $image`.txt $image
    done
}

function merge_text_from_separate_pages() {
    textDirectory=$1
    outputFile=$2
    for text in $(eval "echo ${textDirectory}/*.txt")
    do
	cat $text >> $2
        echo "" >> $2
	echo "" >> $2
    done    
}

function outputMessage() {
    echo $DELIMITER
    echo $1
    echo $DELIMITER
}

function run() {
    inputPdf=$1
    workingDirectory=`get_working_directory_path`
    pagesDirectory=`get_pages_directory_path`
    imagesDirectory=`get_images_directory_path`
    textDirectory=`get_text_directory_path`
    language=`get_default_language`
    outputFile=$2

    outputMessage $startProcessingMessage
    create_directory $workingDirectory
    create_directory $pagesDirectory
    split_multipage_pdf_to_separate_pages $inputPdf $pagesDirectory
    create_directory $imagesDirectory
    generate_images_for_all_pages $pagesDirectory $imagesDirectory
    create_directory $textDirectory
    ocr_images $imagesDirectory $textDirectory $language
    merge_text_from_separate_pages $textDirectory $outputFile
    remove_directory $workingDirectory
    outputMessage $endProcessingMessage
}


#
# main
#

if [ $# -ne 2 ]
then
    echo "Usage: `basename $0` {inputFile} {outputFile}"
    echo "inputFile - input pdf file"
    echo "outputFile - output text file"
    exit $E_BADARGS
fi

inputFile=$1
outputFile=$2
if [ -e $inputFile ]
then
    if [ -e $outputFile ]
    then
	echo "output file \"$outputFile\" already exists"
    else
	run $inputFile $outputFile	
    fi
else
    echo "input file \"$inputFile\" does not exists"
fi