ENH: adding polygon surface computation method.

Code/Common/otbPolygon.h

@@ -120,6 +120,12 @@ class ITK_EXPORT Polygon
   */
  RegionType GetBoundingRegion(void);
 
+  /**
+  * Return the polygon surface.
+  * \return The surface.
+   */
+ double GetSurface();
+
 protected:
   /** Constructor */
   Polygon() 
@@ -131,11 +137,13 @@ protected:
  /**PrintSelf method */
   virtual void PrintSelf(std::ostream& os, itk::Indent indent) const;
 
+  
 private:
   Polygon(const Self&); //purposely not implemented
   void operator=(const Self&); //purposely not implemented
 
   double m_Epsilon;
+  double m_Surface;
 };
 }// End namespace otb
 

Code/Common/otbPolygon.txx

@@ -473,6 +473,50 @@ Polygon<TValue>
   return region;
 }
 
+
+/**
+ * Surface computation including non convex polygons
+ */
+template<class TValue>
+    double
+    Polygon<TValue>
+  ::GetSurface()
+{
+  m_Surface = 0.0;
+  VertexListIteratorType it =  this->GetVertexList()->Begin();
+  
+  if(this->GetVertexList()->Size()>2)
+  {
+    VertexType origin = it.Value();
+    it++;
+    VertexType pt1 = it.Value();
+    VertexType pt2 = it.Value();
+    
+    while(it != this->GetVertexList()->End())
+    {
+      pt1=pt2;
+      pt2 = it.Value();
+          
+      double vector1x = pt1[0] - origin[0];
+      double vector1y = pt1[1] - origin[1];
+      double vector2x = pt2[0] - origin[0];
+      double vector2y = pt2[1] - origin[1];
+      double crossProdduct = vector1x*vector2y - vector2x*vector1y;
+      m_Surface += crossProdduct;
+      it++;
+    }
+    
+    m_Surface = fabs(m_Surface/2.0);
+
+  }
+  else //if there is strictly less than 3 points, surface is 0
+  {
+    m_Surface = 0.0;
+  }
+  
+  return m_Surface;
+}
+
 /**
  * PrintSelf Method
  */

Testing/Code/Common/CMakeLists.txt

@@ -408,7 +408,7 @@ ADD_TEST(coTuPolygon ${COMMON_TESTS6}
          otbPolygon
 	        ${TEMP}/otbPolygonTest.txt	
 		2 10 7 10 7 9 5 9 5 8 7 8 7 6 9 6 9 5 7 5 7 3 2 3 
-		| 6 10 11 10 11 2 4 2 3 4 8 4 8 7 6 7
+		next 6 10 11 10 11 2 4 2 3 4 8 4 8 7 6 7
 )
 
 #-------- otb::PolyLineImageIterator -----------------------------------------

Testing/Code/Common/otbPolygon.cxx

@@ -42,7 +42,7 @@ int otbPolygon(int argc, char * argv[])
       bool first = true; 
       while ( argv[cpt] != NULL && argv[cpt+1]!= NULL)
       {
-	if(argv[cpt][0]=='|')
+	if(argv[cpt][0]=='n')
 	  {
 	    first = false;
 	    ++cpt;
@@ -132,7 +132,12 @@ int otbPolygon(int argc, char * argv[])
       file<<"Bounding Box 2"<<std::endl; 
       file<<"Index : "<<r2.GetIndex()<<" , Size : "<<r2.GetSize()<<std::endl;
  
-
+      file<<std::endl<<std::endl;
+      file<<"Surface computation : "<<std::endl;
+      file<<"Surface 1 :" << (double) polygon1->GetSurface() << std::endl;
+      file<<"Surface 2 :" << polygon2->GetSurface() << std::endl;
+      
+      
       file.close();
     }