From c04150be35bbbc4591944593d438ed39ea4bca0c Mon Sep 17 00:00:00 2001
From: Alberto Griggio <agriggio@users.noreply.github.com>
Date: Tue, 30 Jan 2018 15:27:56 +0100
Subject: [PATCH] histmatching: slightly improved match for the shadows part of
 the tone curve

---
 rtengine/histmatching.cc | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/rtengine/histmatching.cc b/rtengine/histmatching.cc
index 87eb672c8..60cbda287 100644
--- a/rtengine/histmatching.cc
+++ b/rtengine/histmatching.cc
@@ -86,12 +86,19 @@ void mappingToCurve(const std::vector<int> &mapping, std::vector<double> &curve)
     curve.clear();
     
     const int npoints = 8;
-    int idx = 1;
+    int idx = 15;
     for (; idx < int(mapping.size()); ++idx) {
         if (mapping[idx] >= idx) {
             break;
         }
     }
+    if (idx == int(mapping.size())) {
+        for (idx = 1; idx < int(mapping.size()); ++idx) {
+            if (mapping[idx] >= idx) {
+                break;
+            }
+        }
+    }
     int step = max(int(mapping.size())/npoints, 1);
 
     auto coord = [](int v) -> double { return double(v)/255.0; };