enable aliased lines using stroke-gamma for line_symbolizer - closes #689

bindings/python/mapnik_stroke.cpp

@@ -64,17 +64,21 @@ struct stroke_pickle_suite : boost::python::pickle_suite
     getstate(const stroke& s)
     {
         boost::python::list dashes = get_dashes_list(s);
-        return boost::python::make_tuple(s.get_opacity(),dashes,s.get_line_cap(),s.get_line_join());
+        return boost::python::make_tuple(s.get_opacity(),
+                                         dashes,
+                                         s.get_line_cap(),
+                                         s.get_line_join(),
+                                         s.get_gamma());
     }
 
     static void
     setstate (stroke& s, boost::python::tuple state)
     {
         using namespace boost::python;
-        if (len(state) != 4)
+        if (len(state) != 5)
         {
             PyErr_SetObject(PyExc_ValueError,
-                            ("expected 4-item tuple in call to __setstate__; got %s"
+                            ("expected 5-item tuple in call to __setstate__; got %s"
                              % state).ptr()
                 );
             throw_error_already_set();
@@ -93,8 +97,8 @@ struct stroke_pickle_suite : boost::python::pickle_suite
         }
 
         s.set_line_cap(extract<line_cap_e>(state[2]));
-
         s.set_line_join(extract<line_join_e>(state[3]));
+        s.set_gamma(extract<double>(state[4]));
 
     }
 
@@ -142,6 +146,11 @@ void export_stroke ()
                       &stroke::set_opacity, 
                       "Gets or sets the opacity of this stroke.\n"
                       "The value is a float between 0 and 1.\n")
+        .add_property("gamma",
+                      &stroke::get_gamma,
+                      &stroke::set_gamma, 
+                      "Gets or sets the gamma of this stroke.\n"
+                      "The value is a float between 0 and 1.\n")
         .add_property("line_cap",
                       &stroke::get_line_cap,
                       &stroke::set_line_cap,

include/mapnik/stroke.hpp

@@ -69,6 +69,7 @@ class MAPNIK_DECL stroke
     line_join_e line_join_;
     dash_array dash_;
     double dash_offset_;
+    double gamma_;
 public:
     explicit stroke();
     stroke(color const& c, double width=1.0);
@@ -76,13 +77,12 @@ public:
     stroke& operator=(const stroke& rhs);
 
     void set_color(const color& c);
-        
     color const& get_color() const;
         
     double get_width() const;
     void set_width(double w);
-    void set_opacity(double opacity);
 
+    void set_opacity(double opacity);
     double get_opacity() const;
         
     void set_line_cap(line_cap_e line_cap);
@@ -90,9 +90,13 @@ public:
         
     void set_line_join(line_join_e line_join);
     line_join_e get_line_join() const;
+
+    void set_gamma(double gamma);
+    double get_gamma() const;
         
     void add_dash(double dash,double gap);
     bool has_dash() const;
+
     void set_dash_offset(double offset);
     double dash_offset() const;
     

src/agg/process_line_symbolizer.cpp

@@ -67,7 +67,7 @@ void agg_renderer<T>::process(line_symbolizer const& sym,
     unsigned a=col.alpha();
     renderer ren(renb);
     ras_ptr->reset();
-    ras_ptr->gamma(agg::gamma_linear());
+    ras_ptr->gamma(agg::gamma_linear(0.0, stroke_.get_gamma()));
     
     agg::scanline_p8 sl;
     metawriter_with_properties writer = sym.get_metawriter();

src/load_map.cpp

@@ -1557,6 +1557,9 @@ void map_parser::parse_stroke(stroke & strk, ptree const & sym)
     // stroke-linecap
     optional<line_cap_e> line_cap = get_opt_attr<line_cap_e>(sym, "stroke-linecap");
     if (line_cap) strk.set_line_cap(*line_cap);
+    // stroke-gamma
+    optional<double> gamma = get_opt_attr<double>(sym, "stroke-gamma");
+    if (gamma) strk.set_gamma(*gamma);
     // stroke-dashaffset
     optional<double> offset = get_opt_attr<double>(sym, "stroke-dashoffet");
     if (offset) strk.set_dash_offset(*offset);

src/save_map.cpp

@@ -544,6 +544,14 @@ private:
         {
             set_attr( node, "stroke-linecap", strk.get_line_cap() );
         }
+        if ( strk.get_gamma() != dfl.get_gamma() || explicit_defaults_ )
+        {
+            set_attr( node, "stroke-gamma", strk.get_gamma());
+        }
+        if ( strk.dash_offset() != dfl.dash_offset() || explicit_defaults_ )
+        {
+            set_attr( node, "stroke-dashoffset", strk.dash_offset());
+        }
         if ( ! strk.get_dash_array().empty() )
         {
             std::ostringstream os;
@@ -554,10 +562,6 @@ private:
             }
             set_attr( node, "stroke-dasharray", os.str() );
         }
-        if ( strk.dash_offset() != dfl.dash_offset() || explicit_defaults_ )
-        {
-            set_attr( node, "stroke-dashoffset", strk.dash_offset());
-        }
                 
     }
     void add_metawriter_attributes(ptree &node, symbolizer_base const& sym)

src/stroke.cpp

@@ -51,6 +51,7 @@ stroke::stroke()
       opacity_(1.0),
       line_cap_(BUTT_CAP),
       line_join_(MITER_JOIN),
+      gamma_(1.0),
       dash_(),
       dash_offset_(0) {}
 
@@ -60,6 +61,7 @@ stroke::stroke(color const& c, double width)
       opacity_(1.0),
       line_cap_(BUTT_CAP),
       line_join_(MITER_JOIN),
+      gamma_(1.0),
       dash_(),
       dash_offset_(0.0) {}
 
@@ -69,6 +71,7 @@ stroke::stroke(stroke const& other)
       opacity_(other.opacity_),
       line_cap_(other.line_cap_),
       line_join_(other.line_join_),
+      gamma_(other.gamma_),
       dash_(other.dash_), 
       dash_offset_(other.dash_offset_) {}
 
@@ -130,6 +133,16 @@ line_join_e stroke::get_line_join() const
     return line_join_;
 }
 
+void stroke::set_gamma(double gamma)
+{
+    gamma_ = gamma;
+}
+
+double stroke::get_gamma() const
+{
+    return gamma_;
+}
+
 void stroke::add_dash(double dash, double gap)
 {
     dash_.push_back(std::make_pair(dash,gap));
@@ -152,7 +165,7 @@ double stroke::dash_offset() const
 
 dash_array const& stroke::get_dash_array() const
 {
-    return  dash_;
+    return dash_;
 }
 
 void stroke::swap(const stroke& other) throw()
@@ -162,6 +175,8 @@ void stroke::swap(const stroke& other) throw()
     opacity_=other.opacity_;
     line_cap_=other.line_cap_;
     line_join_=other.line_join_;
+    gamma_=other.gamma_;
     dash_ = other.dash_;
+    dash_offset_ = other.dash_offset_;
 }
 }

tests/data/good_maps/line_symbolizer.xml

@@ -0,0 +1,22 @@
+<Map background-color="steelblue" srs="+proj=longlat +ellps=airy +datum=OSGB36 +no_defs">
+
+  <Style name="test">
+    <Rule>
+       <!-- big, thick, aliased lines -->
+      <LineSymbolizer stroke="white" stroke-gamma="0" stroke-width="10"/>
+
+       <!-- small, clean, aliased lines -->
+      <LineSymbolizer stroke="red" stroke-gamma="1" stroke-width=".5"/>
+
+    </Rule>  
+  </Style>
+
+  <Layer name="lay" srs="+proj=longlat +ellps=airy +datum=OSGB36 +no_defs">
+    <StyleName>test</StyleName>
+    <Datasource base="shp">
+      <Parameter name="type">shape</Parameter>
+      <Parameter name="file">../../data/shp/poly.shp</Parameter>
+    </Datasource>
+  </Layer>
+  
+</Map>

tests/python_tests/object_test.py

@@ -153,12 +153,15 @@ def test_stroke_init():
     eq_(s.color, mapnik2.Color('black'))
     eq_(s.line_cap, mapnik2.line_cap.BUTT_CAP)
     eq_(s.line_join, mapnik2.line_join.MITER_JOIN)
+    eq_(s.gamma,1.0)
 
     s = mapnik2.Stroke(mapnik2.Color('blue'), 5.0)
+    s.gamma = .5
 
     eq_(s.width, 5)
     eq_(s.opacity, 1)
     eq_(s.color, mapnik2.Color('blue'))
+    eq_(s.gamma, .5)
     eq_(s.line_cap, mapnik2.line_cap.BUTT_CAP)
     eq_(s.line_join, mapnik2.line_join.MITER_JOIN)