From 2f45de8feaaf5dcf6eab44aaabd01cf2ea824953 Mon Sep 17 00:00:00 2001
From: Dane Springmeyer <dane@dbsgeo.com>
Date: Thu, 5 Jul 2012 17:06:41 -0700
Subject: [PATCH] serialize comp-op in save_map - refs #1292

---
 include/mapnik/image_compositing.hpp |  1 +
 src/image_compositing.cpp            | 11 +++++++++++
 src/save_map.cpp                     | 11 +++++++++++
 3 files changed, 23 insertions(+)

diff --git a/include/mapnik/image_compositing.hpp b/include/mapnik/image_compositing.hpp
index 65f173ba3..c4fbef407 100644
--- a/include/mapnik/image_compositing.hpp
+++ b/include/mapnik/image_compositing.hpp
@@ -79,6 +79,7 @@ enum composite_mode_e
 };
 
 MAPNIK_DECL boost::optional<composite_mode_e> comp_op_from_string(std::string const& name);
+MAPNIK_DECL boost::optional<std::string> comp_op_to_string(composite_mode_e comp_op);
 
 template <typename T1, typename T2>
 MAPNIK_DECL void composite(T1 & dst, T2 & src,
diff --git a/src/image_compositing.cpp b/src/image_compositing.cpp
index 8eff43bb5..e6c64100e 100644
--- a/src/image_compositing.cpp
+++ b/src/image_compositing.cpp
@@ -88,6 +88,17 @@ boost::optional<composite_mode_e> comp_op_from_string(std::string const& name)
     return mode;
 }
 
+boost::optional<std::string> comp_op_to_string(composite_mode_e comp_op)
+{
+    boost::optional<std::string> mode;
+    comp_op_lookup_type::left_const_iterator left_iter = comp_lookup.left.find(comp_op);
+    if (left_iter != comp_lookup.left.end())
+    {
+        mode.reset(left_iter->second);
+    }
+    return mode;
+}
+
 template <typename T1, typename T2>
 void composite(T1 & dst, T2 & src, composite_mode_e mode,
                float opacity,
diff --git a/src/save_map.cpp b/src/save_map.cpp
index 5cd1c4756..6006a903c 100644
--- a/src/save_map.cpp
+++ b/src/save_map.cpp
@@ -31,6 +31,7 @@
 #include <mapnik/text_placements/simple.hpp>
 #include <mapnik/text_placements/list.hpp>
 #include <mapnik/text_placements/dummy.hpp>
+#include <mapnik/image_compositing.hpp>
 
 // boost
 #include <boost/algorithm/string.hpp>
@@ -538,6 +539,16 @@ void serialize_style( ptree & map_node, Map::const_style_iterator style_it, bool
         set_attr(style_node, "opacity", opacity);
     }
 
+    boost::optional<composite_mode_e> comp_op = style.comp_op();
+    if (comp_op)
+    {
+        set_attr(style_node, "comp-op", *comp_op_to_string(*comp_op));
+    }
+    else if (explicit_defaults)
+    {
+        set_attr(style_node, "comp-op", "src-over");
+    }
+
     rules::const_iterator it = style.get_rules().begin();
     rules::const_iterator end = style.get_rules().end();
     for (; it != end; ++it)