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：

CMAKE_MINIMUM_REQUIRED(VERSION 2.8) PROJECT(ImageResliceExample) FIND_PACKAGE(VTK REQUIRED) INCLUDE(${VTK_USE_FILE}) ADD_EXECUTABLE(ImageResliceExample ImageResliceExample.cpp) TARGET_LINK_LIBRARIES(ImageResliceExample ${VTK_LIBRARIES})

ImageResliceExample.cpp文件代码如下：

#include <vtkSmartPointer.h> #include <vtkImageReader2.h> #include <vtkMatrix4x4.h> #include <vtkImageReslice.h> #include <vtkLookupTable.h> #include <vtkImageMapToColors.h> #include <vtkImageActor.h> #include <vtkRenderer.h> #include <vtkRenderWindow.h> #include <vtkRenderWindowInteractor.h> #include <vtkInteractorStyleImage.h> #include <vtkCommand.h> #include <vtkImageData.h> #include <vtkMetaImageReader.h> #include <vtkImageCast.h> class vtkImageInteractionCallback : public vtkCommand { public: static vtkImageInteractionCallback *New() { return new vtkImageInteractionCallback; } vtkImageInteractionCallback() { this->Slicing = 0; this->ImageReslice = 0; this->Interactor = 0; } void SetImageReslice(vtkImageReslice *reslice) { this->ImageReslice = reslice; } void SetImageMapToColors(vtkImageMapToColors *mapToColors) { this->mapToColors = mapToColors; } vtkImageReslice *GetImageReslice() { return this->ImageReslice; } void SetInteractor(vtkRenderWindowInteractor *interactor) { this->Interactor = interactor; } vtkRenderWindowInteractor *GetInteractor() { return this->Interactor; } virtual void Execute(vtkObject *, unsigned long event, void *) { vtkRenderWindowInteractor *interactor = this->GetInteractor(); int lastPos[2]; interactor->GetLastEventPosition(lastPos); int currPos[2]; interactor->GetEventPosition(currPos); if (event == vtkCommand::LeftButtonPressEvent) { this->Slicing = 1; } else if (event == vtkCommand::LeftButtonReleaseEvent) { this->Slicing = 0; } else if (event == vtkCommand::MouseMoveEvent) { if (this->Slicing) { vtkImageReslice *reslice = this->ImageReslice; // Increment slice position by deltaY of mouse int deltaY = lastPos[1] - currPos[1]; reslice->Update(); double sliceSpacing = reslice->GetOutput()->GetSpacing()[2]; vtkMatrix4x4 *matrix = reslice->GetResliceAxes(); // move the center point that we are slicing through double point[4]; double center[4]; point[0] = 0.0; point[1] = 0.0; point[2] = sliceSpacing * deltaY; point[3] = 1.0; matrix->MultiplyPoint(point, center); matrix->SetElement(0, 3, center[0]); matrix->SetElement(1, 3, center[1]); matrix->SetElement(2, 3, center[2]); mapToColors->Update(); interactor->Render(); } else { vtkInteractorStyle *style = vtkInteractorStyle::SafeDownCast( interactor->GetInteractorStyle()); if (style) { style->OnMouseMove(); } } } } private: int Slicing; vtkImageReslice *ImageReslice; vtkRenderWindowInteractor *Interactor; vtkImageMapToColors *mapToColors; }; int main() { vtkSmartPointer<vtkMetaImageReader> reader = vtkSmartPointer<vtkMetaImageReader>::New(); reader->SetFileName ( "E:\\TestData\\brain.mhd" ); reader->Update(); int extent[6]; double spacing[3]; double origin[3]; reader->GetOutput()->GetExtent(extent); reader->GetOutput()->GetSpacing(spacing); reader->GetOutput()->GetOrigin(origin); double center[3]; center[0] = origin[0] + spacing[0] * 0.5 * (extent[0] + extent[1]); center[1] = origin[1] + spacing[1] * 0.5 * (extent[2] + extent[3]); center[2] = origin[2] + spacing[2] * 0.5 * (extent[4] + extent[5]); static double axialElements[16] = { 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 }; vtkSmartPointer<vtkMatrix4x4> resliceAxes = vtkSmartPointer<vtkMatrix4x4>::New(); resliceAxes->DeepCopy(axialElements); resliceAxes->SetElement(0, 3, center[0]); resliceAxes->SetElement(1, 3, center[1]); resliceAxes->SetElement(2, 3, center[2]); vtkSmartPointer<vtkImageReslice> reslice = vtkSmartPointer<vtkImageReslice>::New(); reslice->SetInputConnection(reader->GetOutputPort()); reslice->SetOutputDimensionality(2); reslice->SetResliceAxes(resliceAxes); reslice->SetInterpolationModeToLinear(); vtkSmartPointer<vtkLookupTable> colorTable = vtkSmartPointer<vtkLookupTable>::New(); colorTable->SetRange(0, 1000); colorTable->SetValueRange(0.0, 1.0); colorTable->SetSaturationRange(0.0, 0.0); colorTable->SetRampToLinear(); colorTable->Build(); vtkSmartPointer<vtkImageMapToColors> colorMap = vtkSmartPointer<vtkImageMapToColors>::New(); colorMap->SetLookupTable(colorTable); colorMap->SetInputConnection(reslice->GetOutputPort()); colorMap->Update(); vtkSmartPointer<vtkImageActor> imgActor = vtkSmartPointer<vtkImageActor>::New(); imgActor->SetInputData(colorMap->GetOutput()); vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New(); renderer->AddActor(imgActor); renderer->SetBackground(1, 1, 1); vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New(); renderWindow->SetSize(500, 500); renderWindow->AddRenderer(renderer); vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor = vtkSmartPointer<vtkRenderWindowInteractor>::New(); vtkSmartPointer<vtkInteractorStyleImage> imagestyle = vtkSmartPointer<vtkInteractorStyleImage>::New(); renderWindowInteractor->SetInteractorStyle(imagestyle); renderWindowInteractor->SetRenderWindow(renderWindow); renderWindowInteractor->Initialize(); vtkSmartPointer<vtkImageInteractionCallback> callback = vtkSmartPointer<vtkImageInteractionCallback>::New(); callback->SetImageReslice(reslice); callback->SetInteractor(renderWindowInteractor); callback->SetImageMapToColors(colorMap); imagestyle->AddObserver(vtkCommand::MouseMoveEvent, callback); imagestyle->AddObserver(vtkCommand::LeftButtonPressEvent, callback); imagestyle->AddObserver(vtkCommand::LeftButtonReleaseEvent, callback); renderWindowInteractor->Start(); return EXIT_SUCCESS; }

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。