Doc update, added images,

Added union/difference docs
Added samples

[SVN r69253]

doc/src/examples/algorithms/intersection_poly_poly.cpp

@@ -0,0 +1,65 @@
+// Boost.Geometry (aka GGL, Generic Geometry Library)
+//
+// Copyright Barend Gehrels 2011, Geodan, Amsterdam, the Netherlands
+// Use, modification and distribution is subject to the Boost Software License,
+// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// Quickbook Example
+
+//[intersection
+//` Shows the intersection of two polygons
+
+#include <iostream>
+#include <deque>
+
+#include <boost/geometry/geometry.hpp>
+#include <boost/geometry/geometries/geometries.hpp>
+#include <boost/geometry/extensions/gis/io/wkt/wkt.hpp>
+
+#include <boost/foreach.hpp>
+/*<-*/ #include "create_svg.hpp" /*->*/
+
+int main()
+{
+    typedef boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > polygon;
+
+    polygon green, blue;
+
+    boost::geometry::read_wkt(
+        "POLYGON((2 1.3,2.4 1.7,2.8 1.8,3.4 1.2,3.7 1.6,3.4 2,4.1 3,5.3 2.6,5.4 1.2,4.9 0.8,2.9 0.7,2 1.3)"
+            "(4.0 2.0, 4.2 1.4, 4.8 1.9, 4.4 2.2, 4.0 2.0))", green);
+
+    boost::geometry::read_wkt(
+        "POLYGON((4.0 -0.5 , 3.5 1.0 , 2.0 1.5 , 3.5 2.0 , 4.0 3.5 , 4.5 2.0 , 6.0 1.5 , 4.5 1.0 , 4.0 -0.5))", blue);
+
+    std::deque<polygon> output;
+    boost::geometry::intersection(green, blue, output);
+
+    int i = 0;
+    std::cout << "green && blue:" << std::endl;
+    BOOST_FOREACH(polygon const& p, output)
+    {
+        std::cout << i++ << ": " << boost::geometry::area(p) << std::endl;
+    }
+
+    /*<-*/ create_svg("intersection.svg", green, blue, output); /*->*/
+    return 0;
+}
+
+//]
+
+
+//[intersection_output
+/*`
+Output:
+[pre
+green && blue:
+0: 2.50205
+
+[$img/algorithms/intersection.png]
+
+]
+*/
+//]
+