diff --git a/OCRmyPDF.sh b/OCRmyPDF.sh
index c338a1ff..c03f7043 100644
--- a/OCRmyPDF.sh
+++ b/OCRmyPDF.sh
@@ -1,29 +1,36 @@
 #!/bin/sh
 
+FILE_INPUT_PDF="$1"
+
 VERSION="alpha0"
 
-# Initialization of configuration parameters
-FILE_INPUT_PDF="$1"
-LOG_ERR="0"		# 0=only error messages
-LOG_INFO="1"		# 1=error messages and some infos
-LOG_DEBUG="2"		# 2=debug level logging
-VERBOSITY="$LOG_ERR"
-LAN="eng"		# language of the PDF file (required to get good OCR results)
-KEEP_TMP="0"		# do not delete the temporary files
-IMG_PREPROCESS="0"	# 0=none
-			# 1=only deskew
-			# 2=full preprocessing for OCR, but only deskew in final PDF
-			# 3=full preprocessing
+# Initialization of constants
+EXIT_BAD_INPUT_FILE="1"		# possible exit codes
+EXIT_MISSING_DEPENDENCY="2"
+EXIT_INVALID_OUPUT_PDFA="3"
+LOG_ERR="0"			# 0=only error messages
+LOG_INFO="1"			# 1=error messages and some infos
+LOG_DEBUG="2"			# 2=debug level logging
+
+# Initialization the configuration parameters with default values
+VERBOSITY="$LOG_ERR"	# default verbosity level
+LAN="eng"		# default language of the PDF file (required to get good OCR results)
+KEEP_TMP="0"		# do not delete the temporary files (default)
+PREPROCESS_DESKEW="1"	# 0=no, 1=yes
+PREPROCESS_CLEAN="2"	# 0=no, 
+			# 1=clean image to improve OCR, but do not put cleaned image in final PDF 
+			# 2=clean image to improve OCR, AND put it in final PDF
 
 # check if the required utilities are installed
-! which gs > /dev/null && echo "Please install ghostcript. Exiting..." && exit 1
-! which identify > /dev/null && echo "Please install ImageMagick. Exiting..." && exit 1  
-! which pdfimages > /dev/null && echo "Please install xpdf. Exiting..." && exit 1
-! which pdftoppm > /dev/null && echo "Please install xpdf. Exiting..." && exit 1
-! which pdftk > /dev/null && echo "Please install pdftk. Exiting..." && exit 1
-! which unpaper > /dev/null && echo "Please install unpaper. Exiting..." && exit 1
-! which tesseract > /dev/null && echo "Please install tesseract and tesseract-data. Exiting..." && exit 1
-
+echo "Checking if all dependencies are installed"
+! command -v gs > /dev/null && echo "Please install ghostcript. Exiting..." && exit $EXIT_MISSING_DEPENDENCY
+! command -v identify > /dev/null && echo "Please install ImageMagick. Exiting..." && exit $EXIT_MISSING_DEPENDENCY
+! command -v pdfimages > /dev/null && echo "Please install xpdf. Exiting..." && exit $EXIT_MISSING_DEPENDENCY
+! command -v pdftoppm > /dev/null && echo "Please install xpdf. Exiting..." && exit $EXIT_MISSING_DEPENDENCY
+! command -v pdftk > /dev/null && echo "Please install pdftk. Exiting..." && exit $EXIT_MISSING_DEPENDENCY
+! command -v unpaper > /dev/null && echo "Please install unpaper. Exiting..." && exit $EXIT_MISSING_DEPENDENCY
+! command -v tesseract > /dev/null && echo "Please install tesseract and tesseract-data. Exiting..." && exit $EXIT_MISSING_DEPENDENCY
+! command -v java > /dev/null && echo "Please install java. Exiting..." && exit $EXIT_MISSING_DEPENDENCY
 
 
 
@@ -36,6 +43,7 @@ FILE_OUTPUT_PDFA="${tmp}/ocred-pdfa.pdf"	# name of the final PDF/A file
 FILE_VALIDATION_LOG="${tmp}/pdf_validation.log"	# log file containing the results of the validation of the PDF/A file
 
 # delete tmp files
+echo "Removing old temporary files"
 rm -r -f "${tmp}"
 mkdir -p "${tmp}"
 
@@ -55,7 +63,8 @@ while read pageSize ; do
 
 	# add leading zeros to the page number
 	page=`printf "%04d" $cpt`
-
+	echo "Processing page $page"
+	
 	# create the name of the required file
 	curOrigImg="$tmp/${page}_Image"		# original image available in the current PDF page 
 						# (the image file may have a different orientation than in the pdf file)
@@ -72,19 +81,21 @@ while read pageSize ; do
 	pdfimages -f $page -l $page -j "$FILE_INPUT_PDF" "$curOrigImg" 1>&2	
 	# count number of extracted images
 	nbImg=`ls -1 "$curOrigImg"* | wc -l`
-	[ $nbImg -ne "1" ] && echo "Not exactly 1 image on page $page. Exiting..." && exit 1
+	[ $nbImg -ne "1" ] && echo "Not exactly 1 image on page $page. Exiting..." && exit $EXIT_BAD_INPUT_FILE
 	
-	# Get the characteristic of the extracted image
+	# Get characteristics of the extracted image
 	curOrigImg01=`ls -1 "$curOrigImg"*`
 	propCurOrigImg01=`identify -format "%w %h %[colorspace]" "$curOrigImg01"`
 	heightCurOrigImg01=`echo "$propCurOrigImg01" | cut -f1 -d" "`
 	widthICurOrigImg01=`echo "$propCurOrigImg01" | cut -f2 -d" "`
 	colorspaceCurOrigImg01=`echo "$propCurOrigImg01" | cut -f3 -d" "`
 	# compute the resolution of the whole page (taking into account all images)
-	dpi=$(($heightCurOrigImg01*72/$heightPDF))
+	dpi_x=$(($widthICurOrigImg01*72/$widthPDF))
+	dpi_y=$(($heightCurOrigImg01*72/$heightPDF))
+	[ "$dpi_x" -ne "$dpi_y" ] && echo "X/Y Resolutions not equal (Not supported currently). Exiting..." && exit $EXIT_BAD_INPUT_FILE
+	dpi="$dpi_x"
 
 	# Identify if page image should be saved as ppm (color) or pgm (gray)
-	echo "Page $page: Extracting image as ppm/pgm (${dpi} dpi)"
 	ext="ppm"
 	opt=""		
 	if [ $colorspaceCurOrigImg01 == "Gray" ]; then
@@ -92,17 +103,31 @@ while read pageSize ; do
 		opt="-gray"
 	fi
 	curImgPixmap="$tmp/$page.$ext"
-	curImgPixmapClean="$tmp/$page.for-ocr.$ext"
+	curImgPixmapDeskewed="$tmp/$page.deskewed.$ext"
+	curImgPixmapClean="$tmp/$page.cleaned.$ext"
 	
 	# extract current page as image with right orientation and resoltution
+	echo "Page $page: Extracting image as $ext file (${dpi} dpi)"
 	pdftoppm -f $page -l $page -r $dpi $opt "$FILE_INPUT_PDF" > "$curImgPixmap"
 
-	# improve quality of the image with unpaper to get better OCR results
-	echo "Page $page: Preprocessing image with unpaper"
-	unpaper --dpi $dpi --mask-scan-size 100 \
-		--no-grayfilter --no-blackfilter --no-mask-center --no-border-align \
-		"$curImgPixmap" "$curImgPixmapClean" 1> /dev/null
-
+	# if requested deskew image (without changing its size in pixel)
+	if [ "$PREPROCESS_DESKEW" -eq "1" ]; then
+		echo "Page $page: Deskewing image"
+		convert "$curImgPixmap" -deskew 40% -gravity center -extent ${heightCurOrigImg01}x${widthICurOrigImg01} "$curImgPixmapDeskewed"
+	else
+		cp "$curImgPixmap" "$curImgPixmapDeskewed"
+	fi
+	
+	# if requested clean image with unpaper to get better OCR results
+	if [ "$PREPROCESS_CLEAN" -ge "1" ]; then
+		echo "Page $page: Cleaning image with unpaper"
+		unpaper --dpi $dpi --mask-scan-size 100 \
+			--no-deskew --no-grayfilter --no-blackfilter --no-mask-center --no-border-align \
+			"$curImgPixmapDeskewed" "$curImgPixmapClean" 1> /dev/null
+	else
+		cp "$curImgPixmapDeskewed" "$curImgPixmapClean"
+	fi
+			
 	# perform OCR
 	echo "Page $page: Performing OCR"
 	tesseract -l "$LAN" "$curImgPixmapClean" "$curHocr" hocr 1> /dev/null 2> /dev/null 
@@ -110,7 +135,12 @@ while read pageSize ; do
 
 	# embed text and image to new pdf file
 	echo "Page $page: Embedding text in PDF"
-	python hocrTransform.py -r $dpi -i "$curImgPixmapClean" "$curHocr" "$curOCRedPDF"
+	if [ "$PREPROCESS_CLEAN" -eq "2" ]; then
+		image4finalPDF="$curImgPixmapClean"
+	else
+		image4finalPDF="$curImgPixmapDeskewed"	
+	fi
+	python hocrTransform.py -r $dpi -i "$image4finalPDF" "$curHocr" "$curOCRedPDF"
 	
 	# delete temporary files created for the current page
 	# to avoid using to much disk space in case of PDF files having many pages
@@ -118,6 +148,7 @@ while read pageSize ; do
 		rm "$curOrigImg"*.*
 		rm "$curHocr"
 		rm "$curImgPixmap"
+		rm "$curImgPixmapDeskewed"
 		rm "$curImgPixmapClean"
 	fi
 	
@@ -135,6 +166,7 @@ pdftk $FILES_OCRed_PDFS cat output "$FILE_OUTPUT_PDF"
 # insert metadata (copy metadata from input file)
 #echo "Output file: Inserting metadata"
 # TODO (may work with pdftk update_info)
+# the name of the file may be used as title
 
 # convert the pdf file to match PDF/A format
 echo "Output file: Conversion to PDF/A" 
@@ -156,10 +188,12 @@ grep -i "Status.*Not well-formed" "$FILE_VALIDATION_LOG" && pdf_valid=0
 
 
 
-	
+
 # delete temporary files
 if [ $KEEP_TMP -eq 0 ]; then
 	rm $FILES_OCRed_PDFS
 	rm "$FILE_SIZE_PAGES"
 	rm "$FILE_OUTPUT_PDF"
-fi
\ No newline at end of file
+fi
+
+exit 0
\ No newline at end of file