From 4d402c5ef14402ff0e6727f51f87539e567133dd Mon Sep 17 00:00:00 2001
From: Jiri Drbalek <jiri.drbalek@firma.seznam.cz>
Date: Fri, 4 Mar 2016 10:58:12 +0000
Subject: [PATCH 1/4] raster scaling: fix accessing out of bounds pixels

---
 include/mapnik/span_image_filter.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/mapnik/span_image_filter.hpp b/include/mapnik/span_image_filter.hpp
index 972558ccf..8559394fa 100644
--- a/include/mapnik/span_image_filter.hpp
+++ b/include/mapnik/span_image_filter.hpp
@@ -81,7 +81,7 @@ public:
 
             int src_x = x >> agg::image_subpixel_shift;
             int src_y = y >> agg::image_subpixel_shift;
-            const value_type* pix = reinterpret_cast<const value_type*>(base_type::source().span(src_x, src_y, 0));
+            const value_type* pix = reinterpret_cast<const value_type*>(base_type::source().span(src_x, src_y, 1));
             if (nodata_value_ && *nodata_value_ == *pix)
             {
                 span->v = *nodata_value_;

From 1054e1bddb2aa4fe3d740a9c2e22fcef62c8481c Mon Sep 17 00:00:00 2001
From: Jiri Drbalek <jiri.drbalek@firma.seznam.cz>
Date: Fri, 4 Mar 2016 15:13:55 +0000
Subject: [PATCH 2/4] raster scaling: check for division by zero

---
 include/mapnik/span_image_filter.hpp | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/include/mapnik/span_image_filter.hpp b/include/mapnik/span_image_filter.hpp
index 8559394fa..ccb4c2ba3 100644
--- a/include/mapnik/span_image_filter.hpp
+++ b/include/mapnik/span_image_filter.hpp
@@ -131,19 +131,27 @@ public:
                 fg_ptr = reinterpret_cast<const value_type*>(base_type::source().next_y());
             }
 
-            fg /= total_weight;
-            if (fg < std::numeric_limits<value_type>::min())
+            if (total_weight == 0)
             {
-                span->v = std::numeric_limits<value_type>::min();
-            }
-            else if (fg > std::numeric_limits<value_type>::max())
-            {
-                span->v = std::numeric_limits<value_type>::max();
+                span->v = *nodata_value_;
             }
             else
             {
-                span->v = static_cast<value_type>(fg);
+                fg /= total_weight;
+                if (fg < std::numeric_limits<value_type>::min())
+                {
+                    span->v = std::numeric_limits<value_type>::min();
+                }
+                else if (fg > std::numeric_limits<value_type>::max())
+                {
+                    span->v = std::numeric_limits<value_type>::max();
+                }
+                else
+                {
+                    span->v = static_cast<value_type>(fg);
+                }
             }
+
             span->a = base_mask;
 
             ++span;

From f1f65664cd9962b27a292a9b010e4e0667846f11 Mon Sep 17 00:00:00 2001
From: Jiri Drbalek <jiri.drbalek@firma.seznam.cz>
Date: Fri, 4 Mar 2016 15:14:01 +0000
Subject: [PATCH 3/4] raster scaling: a bit of optimization

---
 include/mapnik/span_image_filter.hpp | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/include/mapnik/span_image_filter.hpp b/include/mapnik/span_image_filter.hpp
index ccb4c2ba3..0b6fc2dec 100644
--- a/include/mapnik/span_image_filter.hpp
+++ b/include/mapnik/span_image_filter.hpp
@@ -79,16 +79,19 @@ public:
         {
             base_type::interpolator().coordinates(&x, &y);
 
-            int src_x = x >> agg::image_subpixel_shift;
-            int src_y = y >> agg::image_subpixel_shift;
-            const value_type* pix = reinterpret_cast<const value_type*>(base_type::source().span(src_x, src_y, 1));
-            if (nodata_value_ && *nodata_value_ == *pix)
+            if (nodata_value_)
             {
-                span->v = *nodata_value_;
-                span->a = base_mask;
-                ++span;
-                ++base_type::interpolator();
-                continue;
+                int src_x = x >> agg::image_subpixel_shift;
+                int src_y = y >> agg::image_subpixel_shift;
+                const value_type* pix = reinterpret_cast<const value_type*>(base_type::source().span(src_x, src_y, 1));
+                if (*nodata_value_ == *pix)
+                {
+                    span->v = *nodata_value_;
+                    span->a = base_mask;
+                    ++span;
+                    ++base_type::interpolator();
+                    continue;
+                }
             }
 
             x += base_type::filter_dx_int() - radius_x;

From d4ac105eca8e3aa6fd2363922a5bede503bab782 Mon Sep 17 00:00:00 2001
From: Jiri Drbalek <jiri.drbalek@firma.seznam.cz>
Date: Fri, 4 Mar 2016 16:59:12 +0000
Subject: [PATCH 4/4] raster scaling: use mapnik::safe_cast, fixes clipping
 negative floats

---
 include/mapnik/span_image_filter.hpp | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/include/mapnik/span_image_filter.hpp b/include/mapnik/span_image_filter.hpp
index 0b6fc2dec..31217690e 100644
--- a/include/mapnik/span_image_filter.hpp
+++ b/include/mapnik/span_image_filter.hpp
@@ -30,6 +30,8 @@
 
 #include <limits>
 
+#include <mapnik/safe_cast.hpp>
+
 namespace mapnik
 {
 
@@ -140,19 +142,7 @@ public:
             }
             else
             {
-                fg /= total_weight;
-                if (fg < std::numeric_limits<value_type>::min())
-                {
-                    span->v = std::numeric_limits<value_type>::min();
-                }
-                else if (fg > std::numeric_limits<value_type>::max())
-                {
-                    span->v = std::numeric_limits<value_type>::max();
-                }
-                else
-                {
-                    span->v = static_cast<value_type>(fg);
-                }
+                span->v = safe_cast<value_type>(fg / total_weight);
             }
 
             span->a = base_mask;