better resolution handling (fixes #38)
- dpi computation moved to in dedicated function - do not exit in case of resolution mismatch (fixes #38) - comments improved
This commit is contained in:
fritz-hh
+99
-53
@@ -1,5 +1,7 @@
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#!/bin/sh
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##############################################################################
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# Script aimed at OCRing a single page of a PDF file
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#
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# Copyright (c) 2013: fritz-hh from Github (https://github.com/fritz-hh)
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##############################################################################
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@@ -7,69 +9,111 @@
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# Initialization of variables passed by args
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FILE_INPUT_PDF="$1"
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PAGE_INFO="$2"
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NUM_PAGES="$3"
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TMP_FLD="$4"
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VERBOSITY="$5"
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LAN="$6"
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KEEP_TMP="$7"
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PREPROCESS_DESKEW="$8"
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PREPROCESS_CLEAN="$9"
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PREPROCESS_CLEANTOPDF="${10}"
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PDF_NOIMG="${11}"
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TESS_CFG_FILES="${12}"
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FILE_INPUT_PDF="$1" # PDF file containing the page to be OCRed
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PAGE_INFO="$2" # Various characteristics of the page to be OCRed
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NUM_PAGES="$3" # Total number of page of the PDF file (required for logging)
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TMP_FLD="$4" # Folder where the temporary files should be placed
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VERBOSITY="$5" # Requested verbosity
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LAN="$6" # Language of the file to be OCRed
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KEEP_TMP="$7" # Keep the temporary files after processing (helpful for debugging)
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PREPROCESS_DESKEW="$8" # Deskew the page to be OCRed
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PREPROCESS_CLEAN="$9" # Clean the page to be OCRed
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PREPROCESS_CLEANTOPDF="${10}" # Put the cleaned paged in the OCRed PDF
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PDF_NOIMG="${11}" # Request to generate also a pdf page containing only the OCRed text but no image (helpful for debugging)
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TESS_CFG_FILES="${12}" # Specific configuration files to be used by Tesseract during OCRing
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##################################
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# Detect the characteristics of the embedded image
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#
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# Params:
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# return :
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##################################
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imageCharacteristics() {
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local page widthPDF heightPDF nbImg curImg propCurImg widthCurImg heightCurImg colorspaceCurImg tmpval dpi_x dpi_y epsilon dpi
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# width / height of PDF page (in pt)
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page="$1"
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widthPDF="$2"
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heightPDF="$3"
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[ $VERBOSITY -ge $LOG_DEBUG ] && echo "Page $page: size ${heightPDF}x${widthPDF} (h*w in pt)"
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# extract raw image from pdf file to compute resolution
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# unfortunately this image can have another orientation than in the pdf...
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# so we will have to extract it again later using pdftoppm
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pdfimages -f $page -l $page -j "$FILE_INPUT_PDF" "$curOrigImg" 1>&2
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# count number of extracted images
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nbImg=`ls -1 "$curOrigImg"* | wc -l`
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[ $nbImg -ne "1" ] && echo "Page $page: Expecting exactly 1 image on page $page (found $nbImg). Exiting..." >&2 && exit $EXIT_BAD_INPUT_FILE
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# Get characteristics of the extracted image
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curImg=`ls -1 "$curOrigImg"*`
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propCurImg=`identify -format "%w %h %[colorspace]" "$curImg"`
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widthCurImg=`echo "$propCurImg" | cut -f1 -d" "`
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heightCurImg=`echo "$propCurImg" | cut -f2 -d" "`
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colorspaceCurImg=`echo "$propCurImg" | cut -f3 -d" "`
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# switch height/width values if the image has not the right orientation
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# we make here the assumption that vertical/horizontal dpi are equal
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# we will check that later
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if [ $((($heightPDF-$widthPDF)*($heightCurImg-$widthCurImg))) -lt 0 ]; then
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[ $VERBOSITY -ge $LOG_DEBUG ] && echo "Page $page: Extracted image has wrong orientation. Inverting image height/width values"
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tmpval=$heightCurImg
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heightCurImg=$widthCurImg
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widthCurImg=$tmpval
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fi
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[ $VERBOSITY -ge $LOG_DEBUG ] && echo "Page $page: size ${heightCurImg}x${widthCurImg} (h*w pixel)"
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# compute the resolution of the image
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dpi_x=`echo "scale=5;$widthCurImg*72/$widthPDF" | bc`
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dpi_y=`echo "scale=5;$heightCurImg*72/$heightPDF" | bc`
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# check the x,y resolution difference that can be cause by:
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# - the truncated PDF width/height in pt
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# - the precision of dpi values computed above
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epsilon=`echo "scale=5;($widthCurImg*72/$widthPDF^2)+($heightCurImg*72/$heightPDF^2)+0.00002" | bc` # max inaccuracy due to truncation of PDF size in pt
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[ $VERBOSITY -ge $LOG_WARN ] && [ `echo "($dpi_x - $dpi_y) < $epsilon " | bc` -eq 0 -o `echo "($dpi_y - $dpi_x) < $epsilon " | bc` -eq 0 ] \
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&& echo "Page $page: (x/y) resolution mismatch ($dpi_x/$dpi_y). Difference should be less than $epsilon. Taking biggest value"
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# round the dpi values to the nearest integer
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dpi_x=`echo "scale=5;$dpi_x+0.5" | bc` # adding 0.5 is required for rounding
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dpi_x=`echo "scale=0;$dpi_x/1" | bc` # round to the nearest integer
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dpi_y=`echo "scale=5;$dpi_y+0.5" | bc` # adding 0.5 is required for rounding
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dpi_y=`echo "scale=0;$dpi_y/1" | bc` # round to the nearest integer
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# take the biggest x,y dpi value
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[ $dpi_x -ge $dpi_y ] && dpi=$dpi_x || dpi=$dpi_y
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# save the image characteristics
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echo "$dpi $colorspaceCurImg" > $curImgCharacteristics
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return 0
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}
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page=`echo $PAGE_INFO | cut -f1 -d" "`
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[ $VERBOSITY -ge $LOG_INFO ] && echo "Processing page $page / $NUM_PAGES"
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# create the name of the required file
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curOrigImg="$TMP_FLD/${page}_Image" # original image available in the current PDF page
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# (the image file may have a different orientation than in the pdf file)
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curHocr="$TMP_FLD/$page.hocr" # hocr file to be generated by the OCR SW for the current page
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curOCRedPDF="$TMP_FLD/${page}-ocred.pdf" # PDF file containing the image + the OCRed text for the current page
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curOCRedPDFDebug="$TMP_FLD/${page}-debug-ocred.pdf" # PDF file containing data required to find out if OCR worked correctly
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# get width / height of PDF page (in pt)
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widthPDF=`echo $PAGE_INFO | cut -f2 -d" "`
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heightPDF=`echo $PAGE_INFO | cut -f3 -d" "`
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[ $VERBOSITY -ge $LOG_DEBUG ] && echo "Page $page: size ${heightPDF}x${widthPDF} (h*w in pt)"
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# extract raw image from pdf file to compute resolution
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# unfortunately this image can have another orientation than in the pdf...
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# so we will have to extract it again later using pdftoppm
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pdfimages -f $page -l $page -j "$FILE_INPUT_PDF" "$curOrigImg" 1>&2
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# count number of extracted images
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nbImg=`ls -1 "$curOrigImg"* | wc -l`
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[ $nbImg -ne "1" ] && echo "Expecting exactly 1 image on page $page (found $nbImg). Exiting..." >&2 && exit $EXIT_BAD_INPUT_FILE
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# Get characteristics of the extracted image
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curImg=`ls -1 "$curOrigImg"*`
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propCurImg=`identify -format "%w %h %[colorspace]" "$curImg"`
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widthCurImg=`echo "$propCurImg" | cut -f1 -d" "`
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heightCurImg=`echo "$propCurImg" | cut -f2 -d" "`
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colorspaceCurImg=`echo "$propCurImg" | cut -f3 -d" "`
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# switch height/width values if the image has not the right orientation
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# we make here the assumption that vertical/horizontal dpi are equal
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# we will check that later
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if [ $((($heightPDF-$widthPDF)*($heightCurImg-$widthCurImg))) -lt 0 ]; then
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[ $VERBOSITY -ge $LOG_DEBUG ] && echo "Page $page: Extracted image has wrong orientation. Inverting image height/width values"
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tmpval=$heightCurImg
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heightCurImg=$widthCurImg
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widthCurImg=$tmpval
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# create the name of the required temporary files
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curOrigImg="$TMP_FLD/${page}_Image" # original image available in the current PDF page
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# (the image file may have a different orientation than in the pdf file)
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curHocr="$TMP_FLD/$page.hocr" # hocr file to be generated by the OCR SW for the current page
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curOCRedPDF="$TMP_FLD/${page}-ocred.pdf" # PDF file containing the image + the OCRed text for the current page
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curOCRedPDFDebug="$TMP_FLD/${page}-debug-ocred.pdf" # PDF file containing data required to find out if OCR worked correctly
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curImgCharacteristics="$TMP_FLD/${page}-img-characteristics.txt" # Detected characteristics of the embedded image
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# auto-detect the characteristics of the embedded image
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if ! imageCharacteristics "$page" "$widthPDF" "$heightPDF"; then
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echo "problem detected. Exiting...."
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fi
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[ $VERBOSITY -ge $LOG_DEBUG ] && echo "Page $page: size ${heightCurImg}x${widthCurImg} (h*w pixel)"
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# compute the resolution of the image
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dpi_x=`echo "scale=5;$widthCurImg*72/$widthPDF" | bc`
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dpi_y=`echo "scale=5;$heightCurImg*72/$heightPDF" | bc`
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# compute the maximum allowed resolution difference that can be cause by:
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# - the truncated PDF width/height in pt
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# - the precision of dpi values computed above
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epsilon=`echo "scale=5;($widthCurImg*72/$widthPDF^2)+($heightCurImg*72/$heightPDF^2)+0.00002" | bc` # max inaccuracy due to truncation of PDF size in pt
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[ `echo "($dpi_x - $dpi_y) < $epsilon " | bc` -eq 0 -o `echo "($dpi_y - $dpi_x) < $epsilon " | bc` -eq 0 ] \
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&& echo "(x/y) resolution mismatch ($dpi_x/$dpi_y). Difference should be lower than $epsilon. Exiting..." >&2 && exit $EXIT_BAD_INPUT_FILE
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dpi=`echo "scale=5;($dpi_x+$dpi_y)/2+0.5" | bc` # adding 0.5 is required for rounding
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dpi=`echo "scale=0;$dpi/1" | bc` # round to the nearest integer
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# read the image characteristics
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dpi=`cat "$curImgCharacteristics" | cut -f1 -d" "`
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colorspaceCurImg=`cat "$curImgCharacteristics" | cut -f2 -d" "`
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# Identify if page image should be saved as ppm (color) or pgm (gray)
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ext="ppm"
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@@ -88,6 +132,8 @@ curImgPixmapClean="$TMP_FLD/$page.cleaned.$ext"
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&& echo "Could not extract page $page as $ext from \"$FILE_INPUT_PDF\". Exiting..." >&2 && exit $EXIT_OTHER_ERROR
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# if requested deskew image (without changing its size in pixel)
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widthCurImg=$(($dpi*$widthPDF/72))
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heightCurImg=$(($dpi*$heightPDF/72))
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if [ "$PREPROCESS_DESKEW" -eq "1" ]; then
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[ $VERBOSITY -ge $LOG_DEBUG ] && echo "Page $page: Deskewing image"
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! convert "$curImgPixmap" -deskew 40% -gravity center -extent ${widthCurImg}x${heightCurImg} "$curImgPixmapDeskewed" \
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