From 100da304b82cfcf37603620e0796ebd2b7c0ec49 Mon Sep 17 00:00:00 2001
From: Alberto Griggio <agriggio@users.noreply.github.com>
Date: Tue, 27 Mar 2018 14:41:19 +0200
Subject: [PATCH] do not perform histogram matching if the embedded thumbnail
 is too small

Fixes #4467
---
 rtengine/histmatching.cc | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/rtengine/histmatching.cc b/rtengine/histmatching.cc
index d7e80a759..0faa8c357 100644
--- a/rtengine/histmatching.cc
+++ b/rtengine/histmatching.cc
@@ -227,6 +227,13 @@ void RawImageSource::getAutoMatchedToneCurve(const ColorManagementParams &cp, st
             histMatchingCache = outCurve;
             histMatchingParams = cp;
             return;
+        } else if (w * 10 < fw) {
+            if (settings->verbose) {
+                std::cout << "histogram matching: the embedded thumbnail is too small: " << w << "x" << h << std::endl;
+            }
+            histMatchingCache = outCurve;
+            histMatchingParams = cp;
+            return;
         }
         skip = LIM(skip * fh / h, 6, 10); // adjust the skip factor -- the larger the thumbnail, the less we should skip to get a good match
         source.reset(thumb->quickProcessImage(neutral, fh / skip, TI_Nearest));