From d4d535720db237bd26069719efee51faac3ed39d Mon Sep 17 00:00:00 2001
From: heckflosse <heckflosse67@gmx.de>
Date: Tue, 19 Mar 2019 15:09:18 +0100
Subject: [PATCH] Don't apply histogram matching when thumb has less than 19200
 pixels

---
 rtengine/histmatching.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/rtengine/histmatching.cc b/rtengine/histmatching.cc
index 3d1eb1657..48969368f 100644
--- a/rtengine/histmatching.cc
+++ b/rtengine/histmatching.cc
@@ -289,7 +289,10 @@ void RawImageSource::getAutoMatchedToneCurve(const ColorManagementParams &cp, st
             histMatchingCache = outCurve;
             *histMatchingParams = cp;
             return;
-        } else if (w * 32 < fw) {
+        } else if (w * 32 < fw || w * h < 19200) {
+             // Some cameras have extremely small thumbs, for example Canon PowerShot A3100 IS has 128x96 thumbs.
+             // For them we skip histogram matching.
+             // With 160x120 thumbs from RICOH GR DIGITAL 2 it works fine, so we use 19200 as limit.
             if (settings->verbose) {
                 std::cout << "histogram matching: the embedded thumbnail is too small: " << w << "x" << h << std::endl;
             }