add 'premultiplied' property on raster symbolizer to allow user to control (in rare cases) the premultiplied status of images in cases where tiffs mis-report it - closes #1512

bindings/python/mapnik_raster_symbolizer.cpp

@@ -28,6 +28,18 @@
 #include <mapnik/raster_colorizer.hpp>
 #include <mapnik/image_scaling.hpp>
 
+namespace {
+
+// https://github.com/mapnik/mapnik/issues/1367
+PyObject* get_premultiplied_impl(mapnik::raster_symbolizer & sym)
+{
+    boost::optional<bool> premultiplied = sym.premultiplied();
+    if (premultiplied)
+        return ::PyBool_FromLong(*premultiplied);
+    Py_RETURN_NONE;
+}
+
+}
 using mapnik::raster_symbolizer;
 
 void export_raster_symbolizer()
@@ -119,5 +131,17 @@ void export_raster_symbolizer()
                       ">>> r = RasterSymbolizer()\n"
                       ">>> r.mesh_size = 32\n"
             )
+        .add_property("premultiplied",
+                      &get_premultiplied_impl,
+                      &raster_symbolizer::set_premultiplied,
+                      "Get/Set premultiplied status of the source image.\n"
+                      "Can be used to override what the source data reports (when in error)\n"
+                      "\n"
+                      "Usage:\n"
+                      "\n"
+                      ">>> from mapnik import RasterSymbolizer\n"
+                      ">>> r = RasterSymbolizer()\n"
+                      ">>> r.premultiplied = False\n"
+            )
         ;
 }

include/mapnik/raster_symbolizer.hpp

@@ -52,6 +52,8 @@ struct MAPNIK_DECL raster_symbolizer : public symbolizer_base
     double calculate_filter_factor() const;
     unsigned get_mesh_size() const;
     void set_mesh_size(unsigned mesh_size);
+    boost::optional<bool> premultiplied() const;
+    void set_premultiplied(bool premultiplied);
 
 private:
     std::string mode_;
@@ -60,6 +62,7 @@ private:
     raster_colorizer_ptr colorizer_;
     double filter_factor_;
     unsigned mesh_size_;
+    boost::optional<bool> premultiplied_;
 };
 }
 

src/load_map.cpp

@@ -1490,6 +1490,9 @@ void map_parser::parse_raster_symbolizer(rule & rule, xml_node const & sym)
         optional<unsigned> mesh_size = sym.get_opt_attr<unsigned>("mesh-size");
         if (mesh_size) raster_sym.set_mesh_size(*mesh_size);
 
+        // premultiplied status of image
+        optional<boolean> premultiplied = sym.get_opt_attr<boolean>("premultiplied");
+        if (premultiplied) raster_sym.set_premultiplied(*premultiplied);
 
         xml_node::const_iterator cssIter = sym.begin();
         xml_node::const_iterator endCss = sym.end();

src/raster_symbolizer.cpp

@@ -177,6 +177,15 @@ void raster_symbolizer::set_mesh_size(unsigned mesh_size)
     mesh_size_=mesh_size;
 }
 
+void raster_symbolizer::set_premultiplied(bool premultiplied)
+{
+    premultiplied_=premultiplied;
+}
+
+boost::optional<bool> raster_symbolizer::premultiplied() const
+{
+    return premultiplied_;
+}
 
 }
 

src/save_map.cpp

@@ -180,10 +180,18 @@ public:
             set_attr( sym_node, "mesh-size", sym.get_mesh_size() );
         }
 
-        if (sym.get_colorizer()) {
+        if (sym.get_colorizer())
+        {
             serialize_raster_colorizer(sym_node, sym.get_colorizer(),
                                        explicit_defaults_);
         }
+
+        boost::optional<bool> premultiplied = sym.premultiplied();
+        if (premultiplied)
+        {
+            set_attr( sym_node, "premultiplied", *sym.premultiplied());
+        }
+
         serialize_symbolizer_base(sym_node, sym);
     }