c++使用vtk库在二维图像上指定位置画一条直线

在C++中使用VTK库在二维图像上绘制一条直线，通常会涉及到`vtkPolyDataMapper`和`vtkActor`。以下是一个简单的示例，展示如何在二维图像上绘制一条从`(x1, y1)`到`(x2, y2)`的直线：

#include <vtkSmartPointer.h>
#include <vtkPoints.h>
#include <vtkCellArray.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>

// 创建一个二维线的数据结构
vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
points->InsertNextPoint(x1, y1, 0);
points->InsertNextPoint(x2, y2, 0);

// 创建一个cell array来连接这两个点
vtkSmartPointer<vtkCellArray> lines = vtkSmartPointer<vtkCellArray>::New();
lines->InsertNextCell(2); // 线由两个点组成
lines->InsertCellPoint(0);
lines->InsertCellPoint(1);

// 创建一个polydata，包含点和线
vtkSmartPointer<vtkPolyData> polyData = vtkSmartPointer<vtkPolyData>::New();
polyData->SetPoints(points);
polyData->SetLines(lines);

// 创建mapper和actor
vtkSmartPointer<vtkPolyDataMapper> mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
mapper->SetInputData(polyData);

vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
actor->SetMapper(mapper);

// 添加到渲染窗口
vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
renderer->AddActor(actor);

// 创建渲染窗口、交互器和关联它们
vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New();
renderWindow->AddRenderer(renderer);

vtkSmartPointer<vtkRenderWindowInteractor> interactor = vtkSmartPointer<vtkRenderWindowInteractor>::New();
interactor->SetRenderWindow(renderWindow);

// 显示
renderWindow->Render();
interactor->Start();

记得在适当的地方替换`x1`, `y1`, 和 `x2`, `y2`的实际值。