Example VectorDataIO

Examples/IO/VectorDataIOExample.cxx

@@ -18,7 +18,25 @@
 
 //  Software Guide : BeginLatex
 //
-//  Although \ref{DXFExample}
+//  Although specific vector data import approaches, as the one
+//  presented in \ref{DXFExample}, can be useful, it is even more
+//  interesting to have available approaches which are independent of
+//  the input format. Unfortunately, many vector data formats do not
+//  share the models for the data they represent. However, in some
+//  cases, when simple data is stored, it can be decomposed in simple
+//  objects as for instance polylines, polygons and points. This is
+//  the case for the Shapefile and the KML (Keyhole Markup Language),
+//  for instance.
+//
+//  Even though specific reader/writer for Shapefile (and soon KML)
+//  are available in OTB, we designed a generic approach for the IO of
+//  this kind of data.
+//
+//  This example illustrates the use of OTB's vector data IO
+//  framework.
+//
+//  We will start by including the header files for the classes
+//  describing the vector data and the corresponding reader and writer.
 //
 //  Software Guide : EndLatex 
 
@@ -26,6 +44,16 @@
 #include "otbVectorData.h"
 #include "otbVectorDataFileReader.h"
 #include "otbVectorDataFileWriter.h"
+// Software Guide : EndCodeSnippet
+//  Software Guide : BeginLatex
+//
+//  We will also need to include the header files for the classes
+//  which model the individual objects that we get from the vector
+//  data structure.
+//
+//  Software Guide : EndLatex 
+
+// Software Guide : BeginCodeSnippet
 #include "itkPreOrderTreeIterator.h"
 #include "otbObjectList.h"
 #include "otbPolygon.h"
@@ -42,21 +70,58 @@ int main(int argc, char * argv[])
     }
 
   typedef short unsigned int PixelType;
+
+//  Software Guide : BeginLatex
+//
+//  We define the types for the vector data structure and the
+//  corresponding file reader.
+//
+//  Software Guide : EndLatex 
+
+// Software Guide : BeginCodeSnippet  
   typedef otb::VectorData<PixelType,2>           VectorDataType;
-  typedef VectorDataType::Pointer           VectorDataPointerType;
+
   typedef otb::VectorDataFileReader<VectorDataType>
                                                  VectorDataFileReaderType;
-  typedef VectorDataFileReaderType::Pointer   VectorDataFileReaderPointerType;
 
-  typedef VectorDataType::DataTreeType      DataTreeType;
-  typedef DataTreeType::Pointer             DataTreePointerType;
-  typedef itk::PreOrderTreeIterator<DataTreeType>    TreeIteratorType;
+// Software Guide : EndCodeSnippet
+//  Software Guide : BeginLatex
+//
+//  We can now instantiate the reader and read the data.
+//
+//  Software Guide : EndLatex 
 
+// Software Guide : BeginCodeSnippet    
 
-  VectorDataFileReaderPointerType reader = VectorDataFileReaderType::New();
+  VectorDataFileReaderType::Pointer reader = VectorDataFileReaderType::New();
   reader->SetFileName(argv[1]);
   reader->Update();
 
+// Software Guide : EndCodeSnippet
+//  Software Guide : BeginLatex
+//
+//  The vector data obtained from the reader wil provide a tree of
+//  nodes containing the actual objects of the scene. This tree will
+//  be accessed using an \doxygen{itk}{PreOrderTreeIterator}.
+//
+//  Software Guide : EndLatex 
+
+// Software Guide : BeginCodeSnippet    
+  
+  typedef VectorDataType::DataTreeType      DataTreeType;
+  typedef itk::PreOrderTreeIterator<DataTreeType>    TreeIteratorType;
+
+// Software Guide : EndCodeSnippet
+//  Software Guide : BeginLatex
+//
+//  In this example we will only read polygon objects from the input
+//  file before writing them to the output file. We define the type
+//  for the polygon object as well as an iterator to the vertices. The
+//  polygons obtained will be stored in an \doxygen{otb}{ObjectList}.
+//
+//  Software Guide : EndLatex 
+
+// Software Guide : BeginCodeSnippet    
 
   typedef otb::Polygon<PixelType> PolygonType;
   typedef PolygonType::VertexListIteratorType PolygonIteratorType;
@@ -64,12 +129,31 @@ int main(int argc, char * argv[])
 
   typedef PolygonListType::Iterator PolygonListIteratorType;
 
-
   PolygonListType::Pointer polygonList = PolygonListType::New();
+
+// Software Guide : EndCodeSnippet
+//  Software Guide : BeginLatex
+//
+//  We get the data tree and instantiate an iterator to walk through it.
+//
+//  Software Guide : EndLatex 
+
+// Software Guide : BeginCodeSnippet    
   
   TreeIteratorType it(reader->GetOutput()->GetDataTree());
 
   it.GoToBegin();
+
+// Software Guide : EndCodeSnippet
+//  Software Guide : BeginLatex
+//
+//  We check that the current object is a polygon using the
+//  \code{IsPolygonFeature()} method and get its exterior ring in
+//  order to sore it into the list.
+//
+//  Software Guide : EndLatex 
+
+// Software Guide : BeginCodeSnippet    
   
   while(!it.IsAtEnd())
     {
@@ -79,69 +163,96 @@ int main(int argc, char * argv[])
 	}
       ++it;
     }
+
+// Software Guide : EndCodeSnippet
   
   polygonList->PushBack(PolygonType::New());
-  //polygonList->Back()->SetValue(m_LeftViewer->GetNextROILabel());
-  
 
-  typedef VectorDataType::DataNodeType DataNodeType;
 
-  typedef DataNodeType::PointType PointType;
-  typedef DataNodeType::LineType LineType;
-  typedef LineType::VertexType VertexType;
+//  Software Guide : BeginLatex
+//
+//  Before writing the polygons to the output file, we have to build
+//  the vector data structure. This structure will be build up of
+//  nodes. We define the types needed for that.
+//
+//  Software Guide : EndLatex 
 
-  VectorDataType::Pointer data = VectorDataType::New();
- 
-  DataNodeType::Pointer document = DataNodeType::New();
-  DataNodeType::Pointer folder1 = DataNodeType::New();
-  DataNodeType::Pointer folder2 = DataNodeType::New();
-  DataNodeType::Pointer folder3 = DataNodeType::New();
-  DataNodeType::Pointer line = DataNodeType::New();
+// Software Guide : BeginCodeSnippet    
   
+  VectorDataType::Pointer outVectorData = VectorDataType::New();
 
-  document->SetNodeType(otb::DOCUMENT);
-  folder1->SetNodeType(otb::FOLDER);
-  folder2->SetNodeType(otb::FOLDER);
-  folder3->SetNodeType(otb::FOLDER);
-  line->SetNodeType(otb::FEATURE_LINE);
-
-  document->SetNodeId("DOCUMENT");
-  folder1->SetNodeId("FOLDER1");
-  folder2->SetNodeId("FOLDER2");
-  folder3->SetNodeId("FOLDER3");
-  line->SetNodeId("FEATURE_LINE");
-  
-  VertexType p1;
-  p1.Fill(5);
-  
-  VertexType p3;
-  p3.Fill(0);
+  typedef VectorDataType::DataNodeType               DataNodeType;
+
+// Software Guide : EndCodeSnippet
+//  Software Guide : BeginLatex
+//
+//  We fill the data structure with the nodes. The root node is a
+//  document which is composed of folders. A list of polygons can be
+//  seen as a multi polygon object.
+//
+//  Software Guide : EndLatex 
+
+// Software Guide : BeginCodeSnippet    
   
-  VertexType p2;
-  p2[0]=0;
-  p2[1]=10;
+  DataNodeType::Pointer document = DataNodeType::New();
+  document->SetNodeType(otb::DOCUMENT);
+  document->SetNodeId("polygon");
+  DataNodeType::Pointer folder = DataNodeType::New();
+  folder->SetNodeType(otb::FOLDER);
+  DataNodeType::Pointer multiPolygon = DataNodeType::New();
+  multiPolygon->SetNodeType(otb::FEATURE_MULTIPOLYGON);
+
+// Software Guide : EndCodeSnippet
+//  Software Guide : BeginLatex
+//
+//  We assign these objects to the data tree stored by the vector data object.
+//
+//  Software Guide : EndLatex 
 
+// Software Guide : BeginCodeSnippet    
   
-  LineType::Pointer l = LineType::New();
-  l->AddVertex(p1);
-  l->AddVertex(p2);
-  l->AddVertex(p3);
-  line->SetLine(l);
+  DataTreeType::Pointer tree = outVectorData->GetDataTree();
+  DataNodeType::Pointer root = tree->GetRoot()->Get();
+
+  tree->Add(document,root);
+  tree->Add(folder,document);
+  tree->Add(multiPolygon,folder);
+
+// Software Guide : EndCodeSnippet
+//  Software Guide : BeginLatex
+//
+//  We can now iterate through the polygon list and fill the vector
+//  data structure.
+//
+//  Software Guide : EndLatex 
 
+// Software Guide : BeginCodeSnippet      
 
-  DataNodeType::Pointer root = data->GetDataTree()->GetRoot()->Get();
+  for(PolygonListType::Iterator it = polygonList->Begin();
+      it != polygonList->End(); ++it)
+    {
+	  DataNodeType::Pointer newPolygon = DataNodeType::New();
+	  newPolygon->SetPolygonExteriorRing(it.Get());
+	  tree->Add(newPolygon,multiPolygon);
+    }
 
-  data->GetDataTree()->Add(document,root);
-  data->GetDataTree()->Add(folder1,document);
-  data->GetDataTree()->Add(folder2,document);
-  data->GetDataTree()->Add(folder3,document);
-  data->GetDataTree()->Add(line,folder2);
+// Software Guide : EndCodeSnippet
+//  Software Guide : BeginLatex
+//
+//  An finally we write the vector data to a file using a generic
+//  \doxygen{otb}{VectorDataFileWriter}. 
+//
+//  Software Guide : EndLatex 
 
+// Software Guide : BeginCodeSnippet      
+  
   typedef otb::VectorDataFileWriter<VectorDataType> WriterType;
-  WriterType::Pointer writer = WriterType::New();  
+  
+  WriterType::Pointer writer = WriterType::New();
   writer->SetFileName(argv[2]);
-  writer->SetInput(data);
   writer->Update();
 
+// Software Guide : EndCodeSnippet  
+
   return EXIT_SUCCESS;
 }