VTK_Learning_三维图像切片（二）———鼠标交互（回调函数、观察者-命令模式）

- 日理万妓 2023-06-28 15:25 90阅读 0赞

> 学习三维图像切面的提取后，我们可以实现一个稍微复杂的程序——通过滑动鼠标来切换三维图像切片，这也是医学图像处理软件中一个很基本的功能。实现该功能难点是怎样在VTK中控制鼠标来实时提取图像切片。我们采用观察者/命令(Observer/Command)模式机制来实现。  
> VTK中鼠标消息是在交互类型对象（interactorstyle）中响应，因此通过为交互类型对象（interactorstyle）添加观察者（observer）来监听相应的消息，当消息触发时，由命令模式执行相应的回调函数。

# 1.鼠标滑动提取三维图像切片--重新定义切片中心 #

>     //记下鼠标Y向变化的幅值大小
>     int deltaY = lastPos[1] - currPos[1];
>     
>     //记下鼠标X向变化的幅值大小
>     int deltaX = lastPos[0] - currPos[0];
>     
>     //reslice->Update();
>     double sliceSpacing = reslice->GetOutput()->GetSpacing()[2];
>     vtkMatrix4x4 *matrix = reslice->GetResliceAxes();
>     //重新定位切片需要经过的中心点
>     double point[4];
>     double center[4];
>     point[0] = 0;
>     point[1] = 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]);
> 
> 鼠标竖直滑动重新定义切片的中心位置。注意：理解MultiplyPoint 是两个矩阵相乘，表示  center4\*1  =  matrix4\*4  乘以  point4\*1。

#  2.鼠标滑动设置窗宽、窗位--重新定义窗位的位置 #

>     static double colorWindowLevel = 500;
>     static double colorWindowWith = 2000;
>     colorWindowLevel += deltaX;
>     
>     colorMap->GetLookupTable()->SetRange(colorWindowLevel - colorWindowWith / 2, colorWindowLevel + colorWindowWith / 2);
> 
> 鼠标横着滑动，会改变窗位的位置，而窗宽是固定不变的。
> 
>  
> 
> 关于窗宽、窗位的理解：
> 
> 窗宽、窗位不是指可视化的窗口的宽度，而是指设置CT图像的灰度值的范围，用于可视化的灰度值范围，CT灰度值范围是0到65536。窗位定以后，根据窗宽值，则可视化的灰度值范围：\[窗位-窗宽/2,窗位+窗宽/2\]
> 
> 见链接：[https://www.cnblogs.com/vranger/p/3806956.html][https_www.cnblogs.com_vranger_p_3806956.html]

#  3.代码 #

>     #include <vtkAutoInit.h>
>     VTK_MODULE_INIT(vtkRenderingOpenGL2);
>     
>     #include <vtkSmartPointer.h>
>     #include <vtkMetaImageReader.h>
>     #include <vtkDicomImageReader.h>
>     #include <vtkMatrix4x4.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> //建立“观察者/命令”模式监听鼠标消息 完成交互
>     #include <vtkImageReslice.h>
>     #include <vtkImageData.h>
>     class vtkImageInteractionCallback : public vtkCommand
>     {
>     public:
>     	static vtkImageInteractionCallback *New() //回调函数初始化函数
>     	{
>     		return new vtkImageInteractionCallback;
>     	}
>     	vtkImageInteractionCallback()
>     	{
>     		this->Slicing = 0;
>     		this->ImageReslice = 0;
>     		this->Interactor = 0;
>     	}
>     	void SetImageReslice(vtkImageReslice *reslice)
>     	{
>     		this->ImageReslice = reslice;
>     	}
>     	vtkImageReslice *GetImageReslice()
>     	{
>     		return this->ImageReslice;
>     	}
>     
>     	void SetImageResliceColorMap(vtkImageMapToColors * colorMap)
>     	{
>     		this->colorMap= colorMap;
>     	}
>     	vtkImageMapToColors *GetImageResliceColorMap()
>     	{
>     		return this->colorMap;
>     	}
>     	void SetInteractor(vtkRenderWindowInteractor *interactor)
>     	{
>     		this->Interactor = interactor;
>     	}
>     	vtkRenderWindowInteractor *GetInteractor()
>     	{
>     		return  this->Interactor;
>     	}
>     	virtual void Execute(vtkObject *, unsigned long event, void *)
>     	{
>     		vtkRenderWindowInteractor *interactor = GetInteractor();
>     		int lastPos[2];
>     		interactor->GetLastEventPosition(lastPos);
>     		int currPos[2];
>     		interactor->GetEventPosition(currPos);
>     
>     		if (event == vtkCommand::LeftButtonPressEvent)
>     		{
>     			this->Slicing = 1; //标志位 
>     		}
>     		else if (event == vtkCommand::LeftButtonReleaseEvent)
>     		{
>     			this->Slicing = 0; //标志位 
>     		}
>     		else if (event == vtkCommand::MouseMoveEvent)
>     		{
>     			if (this->Slicing)//检验鼠标左键已经按下 正在执行操作
>     			{
>     				vtkImageReslice *reslice = this->ImageReslice;
>     
>     				//记下鼠标Y向变化的幅值大小
>     				int deltaY = lastPos[1] - currPos[1];
>     
>     				//记下鼠标X向变化的幅值大小
>     				int deltaX = lastPos[0] - currPos[0];
>     
>     				//reslice->Update();
>     				double sliceSpacing = reslice->GetOutput()->GetSpacing()[2];
>     				vtkMatrix4x4 *matrix = reslice->GetResliceAxes();
>     				//重新定位切片需要经过的中心点
>     				double point[4];
>     				double center[4];
>     				point[0] = 0;
>     				point[1] = 0;
>     				point[2] = sliceSpacing * deltaY;
>     				point[3] = 1.0;
>     				matrix->MultiplyPoint(point, center);
>     
>     				//***********理解MultiplyPoint   center4*1  =  matrix4*4  乘以  point4*1
>     				for (int i = 0;  i < 4; i++)
>     				{
>     					for (int j = 0; j < 4;j++)
>     					{
>     						std::cout << matrix->GetElement(i,j)<< "\t";
>     					}
>     					std::cout << "\n";
>     				}
>     				std::cout << "\n";
>     				std::cout << point[0] << "\t" << point[1] << "\t" << point[2] << "\t" << point[3] << "\n";
>     				std::cout << center[0] << "\t" << center[1] << "\t" << center[2] << "\t" << center[3] << "\n";
>     
>     				//******************
>     
>     				matrix->SetElement(0, 3, center[0]);
>     				matrix->SetElement(1, 3, center[1]);
>     				matrix->SetElement(2, 3, center[2]);
>     				static double colorWindowLevel = 500;
>     				static double colorWindowWith = 2000;
>     				colorWindowLevel += deltaX;
>     
>     				colorMap->GetLookupTable()->SetRange(colorWindowLevel - colorWindowWith / 2, colorWindowLevel + colorWindowWith / 2);
>     
>     				reslice->Update();
>     				colorMap->Update();
>     				interactor->Render();
>     			}
>     			else
>     			{
>     				vtkInteractorStyle *style = vtkInteractorStyle::SafeDownCast(
>     					interactor->GetInteractorStyle());
>     				if (style)
>     				{
>     					style->OnMouseMove();
>     				}
>     			}
>     		}
>     	}
>     private:
>     	int Slicing;
>     	vtkImageReslice *ImageReslice;
>     	vtkImageMapToColors * colorMap;
>     	vtkRenderWindowInteractor *Interactor;
>     };
>     //**********************************************************************************//
>     
>     
>     
>     
>     
>     #include <array>
>     
>     //IMPLEMENT_UEG_NAV_LOGGER(main)
>     
>     int main(int argc, char *argv[])
>     {
>     	vtkSmartPointer<vtkDICOMImageReader> reader = vtkSmartPointer<vtkDICOMImageReader>::New(); //创建读取dicom图片指针对象
>     	reader->SetDirectoryName("D:/workSpace/DICM/sunguihua/SGH"); //设置医学图像文件夹路径
>     	reader->SetDataByteOrderToLittleEndian();
>     	reader->Update();
>     	cout << "读取数据完成" << endl;
>     
>     
>     	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(-500,1500);
>     	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(0.4, 0.5, 0.6);
>     
>     	vtkSmartPointer<vtkRenderWindow> renderWindow =
>     		vtkSmartPointer<vtkRenderWindow>::New();
>     	renderWindow->AddRenderer(renderer);
>     	renderWindow->Render();
>     	renderWindow->SetSize(640, 480);
>     	renderWindow->SetWindowName("Extract3Dslice");
>     
>     	vtkSmartPointer<vtkRenderWindowInteractor> rwi =
>     		vtkSmartPointer<vtkRenderWindowInteractor>::New();
>     	vtkSmartPointer<vtkInteractorStyleImage> imagestyle =
>     		vtkSmartPointer<vtkInteractorStyleImage>::New();
>     	rwi->SetInteractorStyle(imagestyle);
>     	rwi->SetRenderWindow(renderWindow);
>     	rwi->Initialize();
>     	//****************建立 观察者-命令 模式****************//
>     	vtkSmartPointer<vtkImageInteractionCallback> callback =
>     		vtkSmartPointer<vtkImageInteractionCallback>::New();
>     	callback->SetImageReslice(reslice);
>     	callback->SetInteractor(rwi);
>     	callback->SetImageResliceColorMap(colorMap);
>     
>     	imagestyle->AddObserver(vtkCommand::MouseMoveEvent, callback);
>     	imagestyle->AddObserver(vtkCommand::LeftButtonPressEvent, callback);
>     	imagestyle->AddObserver(vtkCommand::LeftButtonReleaseEvent, callback);
>     
>     	rwi->Start();
>     
>     
>     
>     	return 0;
>     
>     }
> 
> vtkImageInteractionCallback继承自vtkCommand类，并覆盖父类函数Execute()。  
> 该类提供了两个接口：SetImageReslice和SetInteractor。  
> SetImageReslice用以设置vtkImageSlice对象，vtkImageSlice根据设置的变换矩阵提取三维图像切片。SetInteractor用以设置vtkRenderWindowInteractor，vtkRenderWindowInteractor类对象负责每次提取切片后刷新视图。  
> 下面重点看Execute函数，该函数提供了具体的切片提取功能。在该函数里面，主要监听了三个消息：  
> vtkCommand::LeftButtonPressEvent，  
> vtkCommand::LeftButtonReleaseEvent，  
> vtkCommand::MouseMoveEvent，  
> 前两个消息分别是鼠标左键的按下和弹起消息。当鼠标左键按下时，就设置切片提取标志为1，而当弹起时，将标志置为0。这样在鼠标移动时，只有在确定切片提取标志为1时，执行切片提取功能。  
> vtkCommand::MouseMoveEvent即为鼠标移动消息。当检测到该消息时，首先检查切片提取标志，当为1时提取切片。提取切片时，需要为vtkImageSlice对象设置变换矩阵。这里在函数开始时，首先获取了鼠标滑动的前后两次点的位置lastPos和currPos。然后根据两点的Y坐标差deltaY，计算新的中心点center并变换至vtkImageSlice当前变换矩阵中，得到变换中心点，将其设置到原来的变换矩阵matrix中，并设置到vtkImageSlice中，最后执行interactor->Render()即可不断的根据鼠标移动刷新图像。
> 
> Command对象定义完毕后，即可为交互对象InteractorStyle添加观察者，响应鼠标消息。  
> 这里主要是定义了vtkImageInteractionCallback对象，并设置vtkImageSlice对象和vtkRenderWindowInteractor对象。然后为交互对象vtkInteractorStyle添加观察者来监控相应的消息，这里主要是三个消息：  
> vtkCommand::LeftButtonPressEvent，  
> vtkCommand::LeftButtonReleaseEvent，  
> vtkCommand::MouseMoveEvent，  
> 当响应到这三个消息时，立即执行vtkImageInteractionCallback的Execute函数，以便实现切片的实时提取和更新。完成以后，运行程序，当鼠标在图像上移动时，会发现图像会跟着鼠标的移动而变化。  
>

# 4.效果图 #

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[https_www.cnblogs.com_vranger_p_3806956.html]: https://www.cnblogs.com/vranger/p/3806956.html
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