From b6ff50a4b0ce2fe546e727f6ea69dfb70122b77d Mon Sep 17 00:00:00 2001
From: Raman Gupta <rocketraman@gmail.com>
Date: Wed, 29 Jul 2020 18:01:20 -0400
Subject: [PATCH] Specify dpi in image header for tesseract

See https://github.com/tesseract-ocr/tesseract/issues/150
---
 README.md    | 4 ++--
 scan_perpage | 4 +++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 474ec19..e805437 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@ Tested and run regularly on Fedora, but should work on other distributions with
 * pnmtops (netpbm-progs)
 * ps2pdf (ghostscript)
 * pdfunite
-* ImageMagick (if --skip-empty-pages) is used
+* ImageMagick (if --skip-empty-pages or --ocr is used)
 
 ### Optional
 
@@ -71,7 +71,7 @@ OPTIONS
  --unpaper
    Run post-processing deskew and black edge detection (requires unpaper)
  --ocr
-   Run OCR to make the PDF searchable (requires tesseract)
+   Run OCR to make the PDF searchable (requires tesseract and ImageMagick)
  --skip-empty-pages
    remove empty pages from resulting PDF document (e.g. one sided doc in duplex mode)
 
diff --git a/scan_perpage b/scan_perpage
index c0ac2bc..0356414 100755
--- a/scan_perpage
+++ b/scan_perpage
@@ -87,7 +87,9 @@ process_page() {
     log "-------------------------------------------------------------------------------"
     if [ $SEARCHABLE -eq 1 ]; then
       log "Converting image data to searchable pdf..."
-      runconstrained tesseract $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE $IMAGE_DIR/${IMAGE_FILE%.*} -l $LANGUAGE pdf | logstdout
+      # tesseract uses the input's DPI header, we need to convert to a format that supports this (like tiff)
+      convert -density ${RESOLUTION}x${RESOLUTION} -units PixelsPerInch $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE $IMAGE_DIR/$PP_PREFIX${IMAGE_FILE}.tiff
+      runconstrained tesseract $IMAGE_DIR/$PP_PREFIX${IMAGE_FILE}.tiff $IMAGE_DIR/${IMAGE_FILE%.*} -l $LANGUAGE pdf | logstdout
     else
       log "Converting image data to pdf..."
       if [ "$PGWIDTHIN" == "" -o "$PGHEIGHTIN" == "" ]; then