VTK vtkImageReslice

三维图像切面提取
　　切片（Slice）或切面是三维图像比较常用的概念，尤其在医学图像中。通过提取切面可以方便地浏览和分析图像内部组织结构。VTK中vtkImageReSlice类可以实现图像切面的提取。在实际开发中，四视图中冠状视面、矢状面和横断面（显示过图像内部一点且平行于XY、YZ、XZ平面的平面），需要用到此类。

示例说明
CMakeLists.txt文件代码如下：

1 CMAKE_MINIMUM_REQUIRED(VERSION 2.8)
2 PROJECT(ImageResliceExample)
3 FIND_PACKAGE(VTK REQUIRED)
4 INCLUDE(${VTK_USE_FILE})
5 ADD_EXECUTABLE(ImageResliceExample  ImageResliceExample.cpp)
6 TARGET_LINK_LIBRARIES(ImageResliceExample ${VTK_LIBRARIES})

ImageResliceExample.cpp文件代码如下：

  1 #include <vtkSmartPointer.h>
  2 #include <vtkImageReader2.h>
  3 #include <vtkMatrix4x4.h>
  4 #include <vtkImageReslice.h>
  5 #include <vtkLookupTable.h>
  6 #include <vtkImageMapToColors.h>
  7 #include <vtkImageActor.h>
  8 #include <vtkRenderer.h>
  9 #include <vtkRenderWindow.h>
 10 #include <vtkRenderWindowInteractor.h>
 11 #include <vtkInteractorStyleImage.h>
 12 #include <vtkCommand.h>
 13 #include <vtkImageData.h>
 14 #include <vtkMetaImageReader.h>
 15 #include <vtkImageCast.h>
 16 
 17 class vtkImageInteractionCallback : public vtkCommand
 18 {
 19 public:
 20     static vtkImageInteractionCallback *New()
 21     {
 22         return new vtkImageInteractionCallback; 
 23     }
 24 
 25     vtkImageInteractionCallback() 
 26     {
 27         this->Slicing = 0;
 28         this->ImageReslice = 0;
 29         this->Interactor = 0; 
 30     }
 31 
 32     void SetImageReslice(vtkImageReslice *reslice) 
 33     {
 34         this->ImageReslice = reslice; 
 35     }
 36 
 37     void SetImageMapToColors(vtkImageMapToColors *mapToColors)
 38     {
 39         this->mapToColors = mapToColors;
 40     }
 41 
 42     vtkImageReslice *GetImageReslice() 
 43     {
 44         return this->ImageReslice;
 45     }
 46 
 47     void SetInteractor(vtkRenderWindowInteractor *interactor) 
 48     {
 49         this->Interactor = interactor;
 50     }
 51 
 52     vtkRenderWindowInteractor *GetInteractor() 
 53     {
 54         return this->Interactor; 
 55     }
 56 
 57     virtual void Execute(vtkObject *, unsigned long event, void *)
 58     {
 59         vtkRenderWindowInteractor *interactor = this->GetInteractor();
 60 
 61         int lastPos[2];
 62         interactor->GetLastEventPosition(lastPos);
 63         int currPos[2];
 64         interactor->GetEventPosition(currPos);
 65 
 66         if (event == vtkCommand::LeftButtonPressEvent)
 67         {
 68             this->Slicing = 1;
 69         }
 70         else if (event == vtkCommand::LeftButtonReleaseEvent)
 71         {
 72             this->Slicing = 0;
 73         }
 74         else if (event == vtkCommand::MouseMoveEvent)
 75         {
 76             if (this->Slicing)
 77             {
 78                 vtkImageReslice *reslice = this->ImageReslice;
 79 
 80                 // Increment slice position by deltaY of mouse
 81                 int deltaY = lastPos[1] - currPos[1];
 82 
 83                 reslice->Update();
 84                 double sliceSpacing = reslice->GetOutput()->GetSpacing()[2];
 85                 vtkMatrix4x4 *matrix = reslice->GetResliceAxes();
 86                 // move the center point that we are slicing through
 87                 double point[4];
 88                 double center[4];
 89                 point[0] = 0.0;
 90                 point[1] = 0.0;
 91                 point[2] = sliceSpacing * deltaY;
 92                 point[3] = 1.0;
 93                 matrix->MultiplyPoint(point, center);
 94                 matrix->SetElement(0, 3, center[0]);
 95                 matrix->SetElement(1, 3, center[1]);
 96                 matrix->SetElement(2, 3, center[2]);
 97                 mapToColors->Update();
 98                 interactor->Render();
 99             }
100             else
101             {
102                 vtkInteractorStyle *style = vtkInteractorStyle::SafeDownCast(
103                     interactor->GetInteractorStyle());
104                 if (style)
105                 {
106                     style->OnMouseMove();
107                 }
108             }
109         }
110     }
111 
112 private:
113     int Slicing;
114     vtkImageReslice *ImageReslice;
115     vtkRenderWindowInteractor *Interactor;
116     vtkImageMapToColors *mapToColors;
117 };
118 
119 int main()
120 {
121     vtkSmartPointer<vtkMetaImageReader> reader =
122         vtkSmartPointer<vtkMetaImageReader>::New();
123     reader->SetFileName ( "E:\\TestData\\brain.mhd" );
124     reader->Update();
125 
126     int extent[6];
127     double spacing[3];
128     double origin[3];
129 
130     reader->GetOutput()->GetExtent(extent);
131     reader->GetOutput()->GetSpacing(spacing);
132     reader->GetOutput()->GetOrigin(origin);
133 
134     double center[3];
135     center[0] = origin[0] + spacing[0] * 0.5 * (extent[0] + extent[1]);
136     center[1] = origin[1] + spacing[1] * 0.5 * (extent[2] + extent[3]);
137     center[2] = origin[2] + spacing[2] * 0.5 * (extent[4] + extent[5]);
138 
139     static double axialElements[16] = {
140         1, 0, 0, 0,
141         0, 1, 0, 0,
142         0, 0, 1, 0,
143         0, 0, 0, 1 
144     };
145 
146     vtkSmartPointer<vtkMatrix4x4> resliceAxes =
147         vtkSmartPointer<vtkMatrix4x4>::New();
148     resliceAxes->DeepCopy(axialElements);
149 
150     resliceAxes->SetElement(0, 3, center[0]);
151     resliceAxes->SetElement(1, 3, center[1]);
152     resliceAxes->SetElement(2, 3, center[2]);
153 
154     vtkSmartPointer<vtkImageReslice> reslice =
155         vtkSmartPointer<vtkImageReslice>::New();
156     reslice->SetInputConnection(reader->GetOutputPort());
157     reslice->SetOutputDimensionality(2);
158     reslice->SetResliceAxes(resliceAxes);
159     reslice->SetInterpolationModeToLinear();
160 
161     vtkSmartPointer<vtkLookupTable> colorTable =
162         vtkSmartPointer<vtkLookupTable>::New();
163     colorTable->SetRange(0, 1000); 
164     colorTable->SetValueRange(0.0, 1.0);
165     colorTable->SetSaturationRange(0.0, 0.0);
166     colorTable->SetRampToLinear();
167     colorTable->Build();
168 
169     vtkSmartPointer<vtkImageMapToColors> colorMap =
170         vtkSmartPointer<vtkImageMapToColors>::New();
171     colorMap->SetLookupTable(colorTable);
172     colorMap->SetInputConnection(reslice->GetOutputPort());
173     colorMap->Update();
174 
175     vtkSmartPointer<vtkImageActor> imgActor =
176         vtkSmartPointer<vtkImageActor>::New();
177     imgActor->SetInputData(colorMap->GetOutput());
178 
179     vtkSmartPointer<vtkRenderer> renderer =
180         vtkSmartPointer<vtkRenderer>::New();
181     renderer->AddActor(imgActor);
182     renderer->SetBackground(1, 1, 1);
183 
184     vtkSmartPointer<vtkRenderWindow> renderWindow =
185         vtkSmartPointer<vtkRenderWindow>::New();
186     renderWindow->SetSize(500, 500);
187     renderWindow->AddRenderer(renderer);
188 
189     vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
190         vtkSmartPointer<vtkRenderWindowInteractor>::New();
191     vtkSmartPointer<vtkInteractorStyleImage> imagestyle =
192         vtkSmartPointer<vtkInteractorStyleImage>::New();
193 
194     renderWindowInteractor->SetInteractorStyle(imagestyle);
195     renderWindowInteractor->SetRenderWindow(renderWindow);
196     renderWindowInteractor->Initialize();
197 
198     vtkSmartPointer<vtkImageInteractionCallback> callback =
199         vtkSmartPointer<vtkImageInteractionCallback>::New();
200     callback->SetImageReslice(reslice);
201     callback->SetInteractor(renderWindowInteractor);
202     callback->SetImageMapToColors(colorMap);
203 
204     imagestyle->AddObserver(vtkCommand::MouseMoveEvent, callback);
205     imagestyle->AddObserver(vtkCommand::LeftButtonPressEvent, callback);
206     imagestyle->AddObserver(vtkCommand::LeftButtonReleaseEvent, callback);
207 
208     renderWindowInteractor->Start();
209     return EXIT_SUCCESS;
210 }

运行结果：

按下鼠标左键，移动鼠标时的gif图片：

代码解释：
先通过vtkMetaImageReader读取一副三维图像，获取图像范围、原点和像素间隔，由这三个参数可以计算图像的中心位置。
接下来定义了切面的变换矩阵axialElements，该矩阵的前三列分别表示X、Y和Z方向矢量，第四列为切面坐标系原点。通过修改切面坐标系原点，可以得到不同位置的切面图像。
然后将读取的图像作为vtkImageReslice的输入，通过函数SetResliceAxes()设置变换矩阵resliceAxis。