From a650caa599600208f6655697f09eb40ac1c508ce Mon Sep 17 00:00:00 2001
From: "James R. Barlow" <jim@purplerock.ca>
Date: Tue, 3 Sep 2019 23:47:20 -0700
Subject: [PATCH] optimize: don't consider 1bpp images for PNG optimization

---
 src/ocrmypdf/optimize.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/ocrmypdf/optimize.py b/src/ocrmypdf/optimize.py
index 5358bd17..e4b4e208 100644
--- a/src/ocrmypdf/optimize.py
+++ b/src/ocrmypdf/optimize.py
@@ -107,6 +107,10 @@ def extract_image_generic(*, pike, root, log, image, xref, options):
         return None
     pim, filtdp = result
 
+    # Don't try to PNG-optimize 1bpp images, since JBIG2 does it better.
+    if pim.bits_per_component == 1:
+        return None
+
     if filtdp[0] == Name.DCTDecode and options.optimize >= 2:
         # This is a simple heuristic derived from some training data, that has
         # about a 70% chance of guessing whether the JPEG is high quality,