VTK 图像平滑_高斯滤波器

1.高斯滤波

高斯平滑的原理类似于均值滤波。均值滤波模板的系数都是一样的，而高斯平滑则是需要根据像素与模板中心的距离来定义权重。权重的计算方法是采用高斯分布，离中心越远，权重越小。

下面是一个利用Gauss滤波进行图像平滑的实例：

 1 #include <vtkAutoInit.h>
 2 VTK_MODULE_INIT(vtkRenderingOpenGL);
 3  
 4 #include <vtkSmartPointer.h>
 5 #include <vtkJPEGReader.h>
 6 #include <vtkImageCast.h>
 7 #include <vtkImageData.h>
 8 #include <vtkImageGaussianSmooth.h>
 9 #include <vtkImageActor.h>
10 #include <vtkRenderer.h>
11 #include <vtkRenderWindow.h>
12 #include <vtkRenderWindowInteractor.h>
13 #include <vtkInteractorStyleImage.h>
14 //#include <vtkImageEllipsoidSource.h>
15  
16 int main()
17 {
18     vtkSmartPointer<vtkJPEGReader> reader =
19         vtkSmartPointer<vtkJPEGReader>::New();
20     reader->SetFileName("lena.jpg");
21     reader->Update();
22  
23     vtkSmartPointer<vtkImageGaussianSmooth> gaussianSmoothFilter =
24         vtkSmartPointer<vtkImageGaussianSmooth>::New();
25     gaussianSmoothFilter->SetInputConnection(reader->GetOutputPort());
26     gaussianSmoothFilter->SetDimensionality(2);
27     gaussianSmoothFilter->SetRadiusFactor(5); //设置模板范围
28     gaussianSmoothFilter->SetStandardDeviation(3);//正态分布/高斯分布标准差
29     gaussianSmoothFilter->Update();
30  
31     vtkSmartPointer<vtkImageActor> originalActor =
32         vtkSmartPointer<vtkImageActor>::New();
33     originalActor->SetInputData(reader->GetOutput());
34  
35     vtkSmartPointer<vtkImageActor> smoothedActor =
36         vtkSmartPointer<vtkImageActor>::New();
37     smoothedActor->SetInputData(gaussianSmoothFilter->GetOutput());
38  
39     double originalViewport[4] = { 0.0, 0.0, 0.5, 1.0 };
40     double smoothedViewport[4] = { 0.5, 0.0, 1.0, 1.0 };
41  
42     vtkSmartPointer<vtkRenderer> originalRenderer =
43         vtkSmartPointer<vtkRenderer>::New();
44     originalRenderer->SetViewport(originalViewport);
45     originalRenderer->AddActor(originalActor);
46     originalRenderer->ResetCamera();
47     originalRenderer->SetBackground(1.0, 0, 0);
48  
49     vtkSmartPointer<vtkRenderer> gradientMagnitudeRenderer =
50         vtkSmartPointer<vtkRenderer>::New();
51     gradientMagnitudeRenderer->SetViewport(smoothedViewport);
52     gradientMagnitudeRenderer->AddActor(smoothedActor);
53     gradientMagnitudeRenderer->ResetCamera();
54     gradientMagnitudeRenderer->SetBackground(1.0, 1.0, 1.0);
55  
56     vtkSmartPointer<vtkRenderWindow> rw =
57         vtkSmartPointer<vtkRenderWindow>::New();
58     rw->AddRenderer(originalRenderer);
59     rw->AddRenderer(gradientMagnitudeRenderer);
60     rw->SetSize(640, 320);
61     rw->SetWindowName("Smooth by Gaussian");
62  
63     vtkSmartPointer<vtkRenderWindowInteractor> rwi =
64         vtkSmartPointer<vtkRenderWindowInteractor>::New();
65     vtkSmartPointer<vtkInteractorStyleImage> style =
66         vtkSmartPointer<vtkInteractorStyleImage>::New();
67     rwi->SetInteractorStyle(style);
68     rwi->SetRenderWindow(rw);
69     rwi->Initialize();
70     rwi->Start();
71  
72     return 0;
73 }

vtkImageGaussianSmooth类默认是执行三维高斯滤波；

SetDimensionality()根据需要设置相应的维数；

SetRadiusFactor()用于设置高斯模板的大小，当超出该模板的范围时，系数取0；

SetStandardDeviation()用于设置高斯分布函数的标准差。

高斯平滑效果如下所示：