From 45cf51f9e8a69fb4534b0b5ae7c193818bc14bd4 Mon Sep 17 00:00:00 2001
From: Raman Gupta <rocketraman@gmail.com>
Date: Fri, 30 Jul 2021 12:48:20 -0400
Subject: [PATCH] Skip empty page detection if optional bc not available

---
 scan         |  5 +++++
 scan_perpage | 12 ++++++------
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/scan b/scan
index be9b23c..836f92a 100755
--- a/scan
+++ b/scan
@@ -242,6 +242,11 @@ if [[ $DESKEW == 1 ]]; then
   DESKEW="--swdeskew=yes"
 fi
 
+if [[ $SKIP_EMPTY_PAGES == 1 && ! -x "$(command -v bc)" ]]; then
+  echo >&2 'Warning: `--skip-empty-pages` specified, but `bc` not available. Disabling empty page detection.'
+  SKIP_EMPTY_PAGES=0
+fi
+
 export VERBOSE
 export UNPAPER
 export SEARCHABLE
diff --git a/scan_perpage b/scan_perpage
index a1793a5..eb0dc80 100755
--- a/scan_perpage
+++ b/scan_perpage
@@ -67,10 +67,10 @@ fi
 process_page() {
   log ""
   log "-------------------------------------------------------------------------------"
-  log "Post-processing scanned page ${IMAGE_PATH}, deskew=$UNPAPER, searchable=$SEARCHABLE..."
+  log "Post-processing scanned page ${IMAGE_PATH}, deskew=$UNPAPER, searchable=$SEARCHABLE, skip-empty-pages=$SKIP_EMPTY_PAGES..."
   log "-------------------------------------------------------------------------------"
 
-  if [[ $SKIP_EMPTY_PAGES -eq 1 ]]; then
+  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"
   else
@@ -78,7 +78,9 @@ process_page() {
   fi
 
   PP_PREFIX=
-  if (( $(echo "$PERCENTAGE_WHITE < 99.8" | bc -l) )); then
+  if [[ $SKIP_EMPTY_PAGES == 1 && $(echo "$PERCENTAGE_WHITE > 99.8" | bc -l) == 1 ]]; then
+    log "Skipping empty page $IMAGE_FILE with white percentage $PERCENTAGE_WHITE"
+  else
     if [[ $UNPAPER == 1 ]]; then
       log "Applying unpaper post-processing to image data..."
       PP_PREFIX="unpaper-"
@@ -105,7 +107,7 @@ process_page() {
       fi
       PNMVERBOSE=
       # older versions of pnmtops (Ubuntu, Debian) don't have the -verbose option, test for it
-      if [[ $VERBOSE = 1 && ! "$(pnmtops -verbose 2>&1 < /dev/null)" =~ "unrecognized option" ]]; then
+      if [[ $VERBOSE == 1 && ! "$(pnmtops -verbose 2>&1 < /dev/null)" =~ "unrecognized option" ]]; then
         PNMVERBOSE="-verbose"
       fi
       log "...Running pnmtops on $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE using page options: $PAGEOPTS"
@@ -114,8 +116,6 @@ process_page() {
       runconstrained $TIMEVERBOSE ps2pdf $PS2PDF_OPTS $IMAGE_DIR/${IMAGE_FILE}.ps $IMAGE_DIR/${IMAGE_FILE}.pdf | logstdout
       [[ -f $IMAGE_DIR/${IMAGE_FILE}.ps ]] && rm $IMAGE_DIR/$PP_PREFIX${IMAGE_FILE}.ps
     fi    
-  else
-    log "Skipping empty page $IMAGE_FILE with white percentage $PERCENTAGE_WHITE"
   fi
 
   status=$?