海拔高度图*.dem文件的读取—vtkDEMReader

vtkDEMReader reads digital elevation files and creates image data. Digital elevation files are produced by the US Geological Survey. A complete description of the DEM file is located at the USGS site. The reader reads the entire dem file and create a vtkImageData that contains a single scalar component that is the elevation in meters. The spacing is also expressed in meters. A number of get methods provide access to fields on the header.

vtkDEMReader 用于读入数字海拔图像文件，并创建图像数据（image data）。数字海拔图形文件，是由US Geological Survey美国的创建。DEM文件的完整描述参见 USGS site。vtkDEMReader类读取完整的dem文件，并创建vtkImageData类对象，在该类对象中包含有一个简单的scalar标量值，该值是以米为单位的海拔高度。空间间隔或间距（spacing）也是以米为单位。在头文件中，有许多get方法可以访问这些参数。

 #ifndef INITIAL_OPENGL
 #define INITIAL_OPENGL
 #include <vtkAutoInit.h>
 VTK_MODULE_INIT(vtkRenderingOpenGL)
 VTK_MODULE_INIT(vtkInteractionStyle)
 #endif
 #include <iostream>
 using namespace std;
 #include "vtkSmartPointer.h"
 #include <vtkSmartPointer.h>
 #include <vtkImageActor.h>
 #include <vtkImageMapToColors.h>
 #include <vtkLookupTable.h>
 #include <vtkDEMReader.h>
 #include <vtkImageData.h>
 #include <vtkImageMapper3D.h>
 #include <vtkRenderWindow.h>
 #include <vtkRenderWindowInteractor.h>
 #include <vtkInteractorStyleImage.h>
 #include <vtkRenderer.h>
 
 int main()
 {
     // Read the file
       vtkSmartPointer<vtkDEMReader> reader = vtkSmartPointer<vtkDEMReader>::New();
       reader->SetFileName("D:/Qt/VTK6.3.0/vtkExampleModelFiles/SainteHelens.dem");
       reader->Update();
 
       vtkSmartPointer<vtkLookupTable> lut = vtkSmartPointer<vtkLookupTable>::New();
       lut->SetHueRange(0.6, );
       lut->SetSaturationRange(1.0, );
       lut->SetValueRange(0.5, 1.0);
       lut->SetTableRange(reader->GetOutput()->GetScalarRange());
       // Visualize
       vtkSmartPointer<vtkImageMapToColors> mapColors = vtkSmartPointer<vtkImageMapToColors>::New();
       mapColors->SetLookupTable(lut);
       mapColors->SetInputConnection(reader->GetOutputPort());
       // Create an actor
       vtkSmartPointer<vtkImageActor> actor =vtkSmartPointer<vtkImageActor>::New();
       actor->GetMapper()->SetInputConnection(mapColors->GetOutputPort());
       // Setup renderer
       vtkSmartPointer<vtkRenderer> renderer =vtkSmartPointer<vtkRenderer>::New();
       renderer->AddActor(actor);
       renderer->ResetCamera();
       // Setup render window
       vtkSmartPointer<vtkRenderWindow> renderWindow =vtkSmartPointer<vtkRenderWindow>::New();
       renderWindow->AddRenderer(renderer);
       // Setup render window interactor
       vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =vtkSmartPointer<vtkRenderWindowInteractor>::New();
       vtkSmartPointer<vtkInteractorStyleImage> style =vtkSmartPointer<vtkInteractorStyleImage>::New();
       renderWindowInteractor->SetInteractorStyle(style);
       // Render and start interaction
       renderWindowInteractor->SetRenderWindow(renderWindow);
       renderWindowInteractor->Initialize();
       renderWindowInteractor->Start();
     return ;
 }