From ff5919be4abbcdd4d1d29125bb2b8f424c880af1 Mon Sep 17 00:00:00 2001
From: heckflosse <heckflosse67@gmx.de>
Date: Mon, 6 Mar 2017 16:52:31 +0100
Subject: [PATCH] Shadows/Highlights: Use iterated boxblur for radius > 40 when
 Sharp mask is disabled, fixes #3730

---
 rtengine/shmap.cc | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/rtengine/shmap.cc b/rtengine/shmap.cc
index 65c1070a2..a92264117 100644
--- a/rtengine/shmap.cc
+++ b/rtengine/shmap.cc
@@ -85,12 +85,21 @@ void SHMap::update (Imagefloat* img, double radius, double lumi[3], bool hq, int
     if (!hq) {
         fillLuminance( img, map, lumi);
 
+        float *buffer = nullptr;
+
+        if(radius > 40.) {
+            // When we pass another buffer to gaussianBlur, it will use iterated boxblur which is less prone to artifacts
+            buffer = new float[W * H];
+        }
+
 #ifdef _OPENMP
         #pragma omp parallel
 #endif
         {
-            gaussianBlur (map, map, W, H, radius);
+            gaussianBlur (map, map, W, H, radius, buffer);
         }
+
+        delete [] buffer;
     }
 
     else {