Merge pull request #38 from surmann/master

Adjust brightness and optimise white page recognition

scan

@@ -31,6 +31,8 @@ DESKEW=0
 DRIVER_OPTION=
 VERBOSE=0
 SKIP_EMPTY_PAGES=0
+WHITE_THRESHOLD=99.8
+BRIGHTNESS_CONTRAST=
 SOURCE=""
 
 TMP_DIR=$(mktemp -d -p "" scan.XXXXXXXXXX)
@@ -86,6 +88,8 @@ while [[ $# > 0 ]]; do
 
   --skip-empty-pages) SKIP_EMPTY_PAGES=1 ;;
 
+  --white-threshold) shift; WHITE_THRESHOLD=$1 ;;
+
   -o|--output) shift; USEOUTPUT=1; OUTPUT="$1" ;;
 
   -l|--outputlist) shift; USEARRAY=1; OUTPUTARR=(); OUTPUTARR+=("$1") ;;
@@ -94,6 +98,8 @@ while [[ $# > 0 ]]; do
 
   -xo|--driver-options) shift; DRIVER_OPTION=$1;;
 
+  --brightness-contrast-sw) shift; BRIGHTNESS_CONTRAST=$1 ;;
+
   *) if [[ $USEARRAY == 1 ]]; then OUTPUTARR+=("$1"); else echo >&2 "Unknown argument: $1"; exit 1; fi ;;
 
   esac
@@ -145,6 +151,11 @@ if [[ $HELP == 1 ]]; then
   echo "   which language to use for OCR"
   echo " --skip-empty-pages"
   echo "   remove empty pages from resulting PDF document (e.g. one sided doc in duplex mode)"
+  echo " --white-threshold"
+  echo "   threshold to identify an empty page is a percentage value between 0 and 100. The default is 99.8"
+  echo " --brightness-contrast-sw"
+  echo "   Alter brightness and contrast via post-processing - prefer specifying brightness and/or"
+  echo "   contrast via --driver-options if supported by your hardware."
   echo ""
   echo "OUTPUT"
   echo " -o, --output <outputfile>"
@@ -267,6 +278,8 @@ export PGWIDTHIN
 export PGHEIGHTIN
 export PS2PDF_OPTS
 export SKIP_EMPTY_PAGES
+export WHITE_THRESHOLD
+export BRIGHTNESS_CONTRAST
 
 if [[ $VERBOSE == 1 ]]; then
   LOCKFILE=$(mktemp)

scan_perpage

@@ -14,6 +14,7 @@ usage()
   echo "  PGWIDTHIN"
   echo "  PGHEIGHTIN"
   echo "  SKIP_EMPTY_PAGES"
+  echo "  BRIGHTNESS_CONTRAST"
   echo "  PS2PDF_OPTS (optional)"
   echo "  VERBOSE (optional)"
   echo "  LOCKFILE (required if VERBOSE=1)"
@@ -67,9 +68,14 @@ fi
 process_page() {
   log ""
   log "-------------------------------------------------------------------------------"
-  log "Post-processing scanned page ${IMAGE_PATH}, deskew=$UNPAPER, searchable=$SEARCHABLE, skip-empty-pages=$SKIP_EMPTY_PAGES..."
+  log "Post-processing scanned page ${IMAGE_PATH}, deskew=$UNPAPER, searchable=$SEARCHABLE, skip-empty-pages=$SKIP_EMPTY_PAGES, white-threshold=$WHITE_THRESHOLD, brightness-contrast-sw=$BRIGHTNESS_CONTRAST..."
   log "-------------------------------------------------------------------------------"
 
+  if [[ "$BRIGHTNESS_CONTRAST" != "" ]]; then
+	log "Adjust brightness and contrast in ImageMagick by $BRIGHTNESS_CONTRAST"
+    convert "$IMAGE_PATH" -brightness-contrast $BRIGHTNESS_CONTRAST "$IMAGE_PATH"
+  fi
+
   if [[ $SKIP_EMPTY_PAGES == 1 ]]; then
     PERCENTAGE_WHITE=$(convert "$IMAGE_PATH" -fuzz 0% -negate -threshold 0 -negate -format "%[fx:100*mean]" info:) || PERCENTAGE_WHITE=0
     log "$IMAGE_PATH has $PERCENTAGE_WHITE % white"
@@ -78,7 +84,7 @@ process_page() {
   fi
 
   PP_PREFIX=
-  if [[ $SKIP_EMPTY_PAGES == 1 && $(echo "$PERCENTAGE_WHITE > 99.8" | bc -l) == 1 ]]; then
+  if [[ $SKIP_EMPTY_PAGES == 1 && $(echo "$PERCENTAGE_WHITE > $WHITE_THRESHOLD" | bc -l) == 1 ]]; then
     log "Skipping empty page $IMAGE_FILE with white percentage $PERCENTAGE_WHITE"
   else
     if [[ $UNPAPER == 1 ]]; then