创建一个带有背景图层和前景图层的渲染窗口

开发环境：

Windows 11 家庭中文版
Microsoft Visual Studio Community 2019
VTK-9.3.0.rc0
vtk-example

demo解决问题：创建一个带有背景图层和前景图层的渲染窗口，知识点：1. 画布转image；2. 渲染图层设置；3. 相机位置、焦点、距离等属性设置

构造imageData对象：程序检查是否提供了输入图像文件名。如果提供了，则使用VTK库中的vtkImageReader2类来读取图像数据，并将其存储在imageData对象中。如果没有提供，则创建一个带有三种颜色的矩形图像。程序使用vtkImageCanvasSource2D类来创建一个画布，并使用其FillBox、FillTriangle和FillTube方法在画布上绘制三种颜色的形状。然后，使用canvasSource->GetOutput()方法获取画布上的图像数据，并将其存储在imageData对象中。
创建了一个vtkImageActor对象imageActor，并将其设置为显示imageData中的图像数据。然后，程序创建了一个vtkRenderer对象backgroundRenderer，并将其设置为显示imageActor中的图像数据。程序还创建了一个vtkSuperquadricSource对象superquadricSource，并使用其SetPhiRoundness和SetThetaRoundness方法设置超椭球体的形状。然后，程序创建了vtkPolyDataMapper和vtkActor对象来显示超椭球体，并使用colors->GetColor3d方法设置超椭球体的颜色。
程序创建了一个vtkRenderer对象sceneRenderer，并将其设置为显示超椭球体。然后，程序创建了一个vtkRenderWindow对象renderWindow，并将其设置为显示backgroundRenderer和sceneRenderer中的内容。程序还使用renderWindow->SetWindowName方法设置窗口名称。
创建了一个vtkRenderWindowInteractor对象renderWindowInteractor，并使用renderWindowInteractor->SetRenderWindow方法将其与renderWindow关联。然后，程序将超椭球体添加到sceneRenderer中，将imageActor添加到backgroundRenderer中。
程序调用renderWindow->Render方法以确定背景相机的位置。程序使用imageData->GetOrigin、imageData->GetSpacing和imageData->GetExtent方法获取图像数据的原点、间距和范围等信息。然后，程序设置相机的位置、焦点和平行比例等参数以使背景相机填充渲染器中的图像。

prj name: BackgroundImage

cpp

# include <vtkActor.h>
# include <vtkCamera.h>
# include <vtkImageActor.h>
# include <vtkImageCanvasSource2D.h>
# include <vtkImageData.h>
# include <vtkImageReader2.h>
# include <vtkImageReader2Factory.h>
# include <vtkNamedColors.h>
# include <vtkNew.h>
# include <vtkPolyDataMapper.h>
# include <vtkProperty.h>
# include <vtkRenderWindow.h>
# include <vtkRenderWindowInteractor.h>
# include <vtkRenderer.h>
# include <vtkSmartPointer.h>
# include <vtkSuperquadricSource.h>

# include <array>

int main(int argc, char* argv[])
{
  vtkNew<vtkNamedColors> colors;

  vtkSmartPointer<vtkImageData> imageData;

  // Verify input arguments.
  if (argc > 1)
  {
    // Read the image
    vtkNew<vtkImageReader2Factory> readerFactory;
    vtkSmartPointer<vtkImageReader2> imageReader;
    imageReader.TakeReference(readerFactory->CreateImageReader2(argv[1]));
    imageReader->SetFileName(argv[1]);
    imageReader->Update();
    imageData = imageReader->GetOutput();
  }
  else
  {

    std::array<double, 3> drawColor1{0, 0, 0};
    std::array<double, 3> drawColor2{0, 0, 0};
    std::array<double, 3> drawColor3{0, 0, 0};
    auto color1 = colors->GetColor3ub("warm_grey").GetData();
    auto color2 = colors->GetColor3ub("DarkCyan").GetData();
    auto color3 = colors->GetColor3ub("LightCoral").GetData();
    for (auto i = 0; i < 3; ++i)
    {
      drawColor1[i] = color1[i];
      drawColor2[i] = color2[i];
      drawColor3[i] = color3[i];
    }

    vtkNew<vtkImageCanvasSource2D> canvasSource;
    canvasSource->SetExtent(0, 100, 0, 100, 0, 0);
    canvasSource->SetScalarTypeToUnsignedChar();
    canvasSource->SetNumberOfScalarComponents(3);
    canvasSource->SetDrawColor(drawColor1.data());
    canvasSource->FillBox(0, 100, 0, 100);
    canvasSource->SetDrawColor(drawColor2.data());
    canvasSource->FillTriangle(10, 10, 25, 10, 25, 25);
    canvasSource->SetDrawColor(drawColor3.data());
    canvasSource->FillTube(75, 75, 0, 75, 5.0);
    canvasSource->Update();
    imageData = canvasSource->GetOutput();
  }
  // Create an image actor to display the image.
  vtkNew<vtkImageActor> imageActor;
  imageActor->SetInputData(imageData);

  // Create a renderer to display the image in the background.
  vtkNew<vtkRenderer> backgroundRenderer;

  // Create a superquadric.
  vtkNew<vtkSuperquadricSource> superquadricSource;
  superquadricSource->SetPhiRoundness(1.1);
  superquadricSource->SetThetaRoundness(.2);

  // Create a mapper and actor.
  vtkNew<vtkPolyDataMapper> superquadricMapper;
  superquadricMapper->SetInputConnection(superquadricSource->GetOutputPort());

  vtkNew<vtkActor> superquadricActor;
  superquadricActor->SetMapper(superquadricMapper);
  superquadricActor->GetProperty()->SetColor(
      colors->GetColor3d("NavajoWhite").GetData());

  vtkNew<vtkRenderer> sceneRenderer;

  vtkNew<vtkRenderWindow> renderWindow;

  // Set up the render window and renderers such that there is
  // a background layer and a foreground layer.
  backgroundRenderer->SetLayer(0);
  backgroundRenderer->InteractiveOff();
  sceneRenderer->SetLayer(1);
  renderWindow->SetNumberOfLayers(2);
  renderWindow->AddRenderer(backgroundRenderer);
  renderWindow->AddRenderer(sceneRenderer);
  renderWindow->SetWindowName("BackgroundImage");

  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  // Add actors to the renderers
  sceneRenderer->AddActor(superquadricActor);
  backgroundRenderer->AddActor(imageActor);

  // Render once to figure out where the background camera will be.
  renderWindow->Render();

  // Set up the background camera to fill the renderer with the image.
  double origin[3];
  double spacing[3];
  int extent[6];
  imageData->GetOrigin(origin);
  imageData->GetSpacing(spacing);
  imageData->GetExtent(extent);

  vtkCamera* camera = backgroundRenderer->GetActiveCamera();
  camera->ParallelProjectionOn();

  double xc = origin[0] + 0.5 * (extent[0] + extent[1]) * spacing[0];
  double yc = origin[1] + 0.5 * (extent[2] + extent[3]) * spacing[1];
  // double xd = (extent[1] - extent[0] + 1)*spacing[0];
  double yd = (extent[3] - extent[2] + 1) * spacing[1];
  double d = camera->GetDistance();
  camera->SetParallelScale(0.5 * yd);
  camera->SetFocalPoint(xc, yc, 0.0);
  camera->SetPosition(xc, yc, d);

  // Render again to set the correct view.
  renderWindow->Render();

  // Interact with the window.
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

创建一个带有背景图层和前景图层的渲染窗口 ​

创建一个带有背景图层和前景图层的渲染窗口