VTK_Learning_图像（融合）混合（Viewport&vtkImageBlend）

1.vtkImageBlend

图像融合利用图像的alpha通道和不透明度来实现。VTK中vtkImageBlend实现图像的融合。

vtkImageBlend可以接收多个图像输入，输出为融合图像。输出图像的像素间隔、原点、范围（extent）以及像素组分个数与第一个图像一致。

该类提供了两种融合模式，默认的融合方式是标准模式。

第二种是混合模式（Compound），该模式下输出结果经过alpha/opacity不透明度的和做过归一化。另外还可以设置一个阈值，当alpha*opacity小于等于该阈值时会忽略该像素。

2.代码

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#include <vtkAutoInit.h>
VTK_MODULE_INIT(vtkRenderingOpenGL);
 
#include <vtkSmartPointer.h>
#include <vtkJPEGReader.h>
//#include <vtkImageCast.h>
#include <vtkImageData.h>
#include <vtkImageCanvasSource2D.h>
#include <vtkImageBlend.h>
#include <vtkImageActor.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkInteractorStyleImage.h>
 
int main()
{
//数据管线
  vtkSmartPointer<vtkJPEGReader> reader =
    vtkSmartPointer<vtkJPEGReader>::New();
  reader->SetFileName("data/lena-gray.jpg");
  reader->Update();
 
  vtkSmartPointer<vtkImageCanvasSource2D> source=
    vtkSmartPointer<vtkImageCanvasSource2D>::New();
  source->SetNumberOfScalarComponents(1);
  source->SetScalarTypeToUnsignedChar();
  source->SetExtent(0,512,0,512,0,0);
  source->SetDrawColor(0,0,0);
  source->FillBox(0,512,0,512);
  source->SetDrawColor(255,255,255);
  source->FillBox(100,400,100,400);
  source->Update();
 
  vtkSmartPointer<vtkImageBlend> blend =
    vtkSmartPointer<vtkImageBlend>::New();
  blend->SetInputData(0,reader->GetOutput());
  blend->SetInputData(1,source->GetOutput());
  blend->SetOpacity(0,0.4);
  blend->SetOpacity(1,0.6);
  blend->Update();
  
//渲染引擎
  vtkSmartPointer<vtkImageActor> actor1 =
    vtkSmartPointer<vtkImageActor>::New();
  actor1->SetInputData(reader->GetOutput());
 
  vtkSmartPointer<vtkImageActor> actor2 =
    vtkSmartPointer<vtkImageActor>::New();
  actor2->SetInputData(source->GetOutput());
 
  vtkSmartPointer<vtkImageActor> blend_actor =
    vtkSmartPointer<vtkImageActor>::New();
  blend_actor->SetInputData(blend->GetOutput());
  //定义视窗大小(xmin.ymin,xmax,ymax)
  //按window的尺寸进行比例分割
  double leftViewport [4] = {0,0,0.33,1};
  double midViewport  [4] = {0.33,0,0.66,1};
  double rightViewport[4] = {0.66,0,1,1};
  //render
  vtkSmartPointer<vtkRenderer> render1 = 
    vtkSmartPointer<vtkRenderer>::New();
  render1->SetViewport(leftViewport);
  render1->AddActor(actor1);
  render1->ResetCamera();
  render1->SetBackground(1,0,0);
 
  vtkSmartPointer<vtkRenderer> render2 = 
    vtkSmartPointer<vtkRenderer>::New();
  render2->SetViewport(midViewport);
  render2->AddActor(actor2);
  render2->ResetCamera();
  render2->SetBackground(0,1,0);
 
  vtkSmartPointer<vtkRenderer> render3 = 
    vtkSmartPointer<vtkRenderer>::New();
  render3->SetViewport(rightViewport);
  render3->AddActor(blend_actor);
  render3->ResetCamera();
  render3->SetBackground(0,0,1);
  //window
  vtkSmartPointer<vtkRenderWindow> renderwindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderwindow->AddRenderer(render1);
  renderwindow->AddRenderer(render2);
  renderwindow->AddRenderer(render3);
  renderwindow->SetSize(640,320);
  renderwindow->SetWindowName("Image-Fusion");
  renderwindow->Render();
  //interactor
  vtkSmartPointer<vtkRenderWindowInteractor> rwi =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  vtkSmartPointer<vtkInteractorStyleImage> style =
    vtkSmartPointer<vtkInteractorStyleImage>::New();
  rwi->SetInteractorStyle(style);
  rwi->SetRenderWindow(renderwindow);
  rwi->Initialize();
  rwi->Start();
 
  return 0;
}