From 181c470bd61a4d7b13f770a175bec6e1b39a598c Mon Sep 17 00:00:00 2001
From: Artem Pavlenko <artem@mapnik.org>
Date: Thu, 24 May 2012 12:51:12 +0100
Subject: [PATCH] + correct calculations

---
 include/mapnik/image_filter.hpp | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/mapnik/image_filter.hpp b/include/mapnik/image_filter.hpp
index 6ff7b997b..a92b91fc7 100644
--- a/include/mapnik/image_filter.hpp
+++ b/include/mapnik/image_filter.hpp
@@ -410,21 +410,21 @@ void x_gradient_impl(Src const& src_view, Dst const& dst_view)
         typename Src::x_iterator src_it = src_view.row_begin(y);
         typename Dst::x_iterator dst_it = dst_view.row_begin(y);
 
-        dst_it[0][0] = 127 + (src_it[0][0] - src_it[1][0]) / 2;
-        dst_it[0][1] = 127 + (src_it[0][1] - src_it[1][1]) / 2;
-        dst_it[0][2] = 127 + (src_it[0][2] - src_it[1][2]) / 2;
+        dst_it[0][0] = 128 + (src_it[0][0] - src_it[1][0]) / 2;
+        dst_it[0][1] = 128 + (src_it[0][1] - src_it[1][1]) / 2;
+        dst_it[0][2] = 128 + (src_it[0][2] - src_it[1][2]) / 2;
 
-        dst_it[dst_view.width()-1][0] = 127 + (src_it[src_view.width()-2][0] - src_it[src_view.width()-1][0]) / 2;
-        dst_it[dst_view.width()-1][1] = 127 + (src_it[src_view.width()-2][1] - src_it[src_view.width()-1][1]) / 2;
-        dst_it[dst_view.width()-1][2] = 127 + (src_it[src_view.width()-2][2] - src_it[src_view.width()-1][2]) / 2;
+        dst_it[dst_view.width()-1][0] = 128 + (src_it[src_view.width()-2][0] - src_it[src_view.width()-1][0]) / 2;
+        dst_it[dst_view.width()-1][1] = 128 + (src_it[src_view.width()-2][1] - src_it[src_view.width()-1][1]) / 2;
+        dst_it[dst_view.width()-1][2] = 128 + (src_it[src_view.width()-2][2] - src_it[src_view.width()-1][2]) / 2;
 
         dst_it[0][3] = dst_it[src_view.width()-1][3] = 255;
 
         for (int x=1; x<src_view.width()-1; ++x)
         {
-            dst_it[x][0] = 127 + (src_it[x-1][0] - src_it[x+1][0]) / 2;
-            dst_it[x][1] = 127 + (src_it[x-1][1] - src_it[x+1][1]) / 2;
-            dst_it[x][2] = 127 + (src_it[x-1][2] - src_it[x+1][2]) / 2;
+            dst_it[x][0] = 128 + (src_it[x-1][0] - src_it[x+1][0]) / 2;
+            dst_it[x][1] = 128 + (src_it[x-1][1] - src_it[x+1][1]) / 2;
+            dst_it[x][2] = 128 + (src_it[x-1][2] - src_it[x+1][2]) / 2;
             dst_it[x][3] = 255;
         }
     }