From 30440104ba498490b5ca6a4fda694ce8aa5b19de Mon Sep 17 00:00:00 2001
From: "James R. Barlow" <james@purplerock.ca>
Date: Fri, 12 Nov 2021 20:09:55 -0800
Subject: [PATCH] Remove --threshold argument

Tesseract is now included better thresholding (binarization) in v5. Users that have
thresholding issues should try that first. If we find further problems
this can be brought back as a plugin.
---
 misc/completion/ocrmypdf.bash |  2 +-
 misc/completion/ocrmypdf.fish |  1 -
 src/ocrmypdf/_pipeline.py     |  8 --------
 src/ocrmypdf/api.py           |  1 -
 src/ocrmypdf/cli.py           |  8 --------
 tests/test_main.py            | 14 --------------
 6 files changed, 1 insertion(+), 33 deletions(-)

diff --git a/misc/completion/ocrmypdf.bash b/misc/completion/ocrmypdf.bash
index b652769e..3683d8f7 100644
--- a/misc/completion/ocrmypdf.bash
+++ b/misc/completion/ocrmypdf.bash
@@ -40,7 +40,7 @@ _ocrmypdf()
             --sidecar --version --jobs --quiet --verbose --title --author
             --subject --keywords --rotate-pages --remove-background --deskew
             --clean --clean-final --unpaper-args --oversample --remove-vectors
-            --threshold --force-ocr --skip-text --redo-ocr
+            --force-ocr --skip-text --redo-ocr
             --skip-big --jpeg-quality --png-quality --jbig2-lossy
             --max-image-mpixels --tesseract-config --tesseract-pagesegmode
             --help --tesseract-oem --pdf-renderer --tesseract-timeout
diff --git a/misc/completion/ocrmypdf.fish b/misc/completion/ocrmypdf.fish
index d4bb76d3..fd1e54a0 100644
--- a/misc/completion/ocrmypdf.fish
+++ b/misc/completion/ocrmypdf.fish
@@ -29,7 +29,6 @@ complete -c ocrmypdf -s d -l deskew -d "fix small horizontal alignment skew"
 complete -c ocrmypdf -s c -l clean -d "clean document images before OCR"
 complete -c ocrmypdf -s i -l clean-final -d "clean document images and keep result"
 complete -c ocrmypdf -l remove-vectors -d "don't send vector objects to OCR"
-complete -c ocrmypdf -l threshold -d "threshold images before OCR"
 
 complete -c ocrmypdf -s f -l force-ocr -d "OCR documents that already have printable text"
 complete -c ocrmypdf -s s -l skip-ocr -d "skip OCR on pages that text, otherwise try OCR"
diff --git a/src/ocrmypdf/_pipeline.py b/src/ocrmypdf/_pipeline.py
index a5f6ba56..af603357 100644
--- a/src/ocrmypdf/_pipeline.py
+++ b/src/ocrmypdf/_pipeline.py
@@ -541,14 +541,6 @@ def create_ocr_image(image: Path, page_context: PageContext):
                 log.debug('blanking %r', pixcoords)
                 draw.rectangle(pixcoords, fill=white)
                 # draw.rectangle(pixcoords, outline=pink)
-
-        if options.threshold:
-            pix = leptonica.Pix.frompil(im)
-            pix = pix.masked_threshold_on_background_norm()
-            im_pix = pix.topil()
-            im_pix.info['dpi'] = im.info['dpi']
-            im = im_pix
-
         del draw
 
         filter_im = page_context.plugin_manager.hook.filter_ocr_image(
diff --git a/src/ocrmypdf/api.py b/src/ocrmypdf/api.py
index 8f731fa3..ac21ebb7 100644
--- a/src/ocrmypdf/api.py
+++ b/src/ocrmypdf/api.py
@@ -228,7 +228,6 @@ def ocr(  # pylint: disable=unused-argument
     unpaper_args: str = None,
     oversample: int = None,
     remove_vectors: bool = None,
-    threshold: bool = None,
     force_ocr: bool = None,
     skip_text: bool = None,
     redo_ocr: bool = None,
diff --git a/src/ocrmypdf/cli.py b/src/ocrmypdf/cli.py
index 87012321..7f01e0e9 100644
--- a/src/ocrmypdf/cli.py
+++ b/src/ocrmypdf/cli.py
@@ -287,14 +287,6 @@ Online documentation is located at:
         help="EXPERIMENTAL. Mask out any vector objects in the PDF so that they "
         "will not be included in OCR. This can eliminate false characters.",
     )
-    preprocessing.add_argument(
-        '--threshold',
-        action='store_true',
-        help=(
-            "EXPERIMENTAL. Threshold image to 1bpp before sending it to Tesseract "
-            "for OCR. Can improve OCR quality compared to Tesseract's thresholder."
-        ),
-    )
 
     ocrsettings = parser.add_argument_group("OCR options", "Control how OCR is applied")
     ocrsettings.add_argument(
diff --git a/tests/test_main.py b/tests/test_main.py
index 50081637..70359cdb 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -869,20 +869,6 @@ def test_image_dpi_not_image(caplog, resources, outpdf):
     assert '--image-dpi is being ignored' in caplog.text
 
 
-def test_image_dpi_threshold(resources, outpdf):
-    check_ocrmypdf(
-        resources / 'typewriter.png',
-        outpdf,
-        '--threshold',
-        '--image-dpi=170',
-        '--output-type=pdf',
-        '--optimize=0',
-        '--plugin',
-        'tests/plugins/tesseract_noop.py',
-    )
-    assert outpdf.exists()
-
-
 def test_outputtype_none_bad_setup(resources, outpdf):
     p, _out, err = run_ocrmypdf(
         resources / 'trivial.pdf',