VTK：图像平滑——各项异性滤波

1.各向异性扩散滤波

高斯平滑方法在平滑噪声的同时，模糊了图像重要的边缘图像。各向异性滤波是一种基于偏微分方程的滤波技术，建立于热量的各向异性扩散理论。各向异性滤波在图像的平坦区域选择大尺度平滑，而边缘区域则选择小尺度的平滑，在抑制噪声的同时保持了图像的边缘信息。
vtkImageAnisotropicDiffusion2D(vtkImageAnisotropicDiffusion3D)实现图像各向异性扩散滤波。

2.代码

#include "Test.h"
#include <vtkAutoInit.h>
VTK_MODULE_INIT(vtkRenderingOpenGL2);
VTK_MODULE_INIT(vtkInteractionStyle);


#include <vtkSmartPointer.h>
#include <vtkJPEGReader.h>
#include <vtkImageCast.h>
#include <vtkImageAnisotropicDiffusion2D.h>
#include <vtkImageActor.h>
#include <vtkCamera.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkInteractorStyleImage.h>

int main()
{
	vtkSmartPointer<vtkJPEGReader> reader =
		vtkSmartPointer<vtkJPEGReader>::New();
	reader->SetFileName("data/Lena.jpg");

	vtkSmartPointer<vtkImageAnisotropicDiffusion2D> diffusion =
		vtkSmartPointer<vtkImageAnisotropicDiffusion2D>::New();
	diffusion->SetInputConnection(reader->GetOutputPort());
	diffusion->SetNumberOfIterations(100);//SetNumberOfIterations()用于设置迭代的次数；vtkImageAnisotropicDiffusion2D通过迭代的方法实现；
	diffusion->SetDiffusionThreshold(5); //小于该阈值扩散 各向异性扩散滤波原理是在梯度较小的像素处进行较大幅度扩散，而在大梯度处则只进行细微的扩散
	diffusion->Update();
	//该类中还有一个梯度标志GradientMagnitudeThreshold，用来设置梯度算子。当该标志开时梯度通过中心差分方法计算；当标志为关时，需要单独处理每个相邻像素。
	//当像素与相邻像素梯度小于DiffusionThreshold时进行扩散处理.

	//创建角色
	vtkSmartPointer<vtkImageActor> originalActor =
		vtkSmartPointer<vtkImageActor>::New();
	originalActor->SetInputData(reader->GetOutput());

	vtkSmartPointer<vtkImageActor> diffusionActor =
		vtkSmartPointer<vtkImageActor>::New();
	diffusionActor->SetInputData(diffusion->GetOutput());

	double leftViewport[4] = { 0.0, 0.0, 0.5, 1.0 };
	double rightViewport[4] = { 0.5, 0.0, 1.0, 1.0 };

	vtkSmartPointer<vtkCamera> camera =
		vtkSmartPointer<vtkCamera>::New();
	vtkSmartPointer<vtkRenderer> leftRenderer =
		vtkSmartPointer<vtkRenderer>::New();
	leftRenderer->SetViewport(leftViewport);
	leftRenderer->AddActor(originalActor);
	leftRenderer->SetBackground(1.0, 0, 0);
	leftRenderer->SetActiveCamera(camera);
	leftRenderer->ResetCamera();

	vtkSmartPointer<vtkRenderer> rightRenderer =
		vtkSmartPointer<vtkRenderer>::New();
	rightRenderer->SetViewport(rightViewport);
	rightRenderer->SetBackground(1.0, 1.0, 1.0);
	rightRenderer->AddActor(diffusionActor);
	rightRenderer->SetActiveCamera(camera);
	//
	vtkSmartPointer<vtkRenderWindow> rw =
		vtkSmartPointer<vtkRenderWindow>::New();
	rw->AddRenderer(leftRenderer);
	rw->AddRenderer(rightRenderer);
	rw->SetSize(640, 320);
	rw->SetWindowName("Smooth by AnistropicFilter");

	vtkSmartPointer<vtkRenderWindowInteractor> rwi =
		vtkSmartPointer<vtkRenderWindowInteractor>::New();
	vtkSmartPointer<vtkInteractorStyleImage> style =
		vtkSmartPointer<vtkInteractorStyleImage>::New();
	rwi->SetInteractorStyle(style);
	rwi->SetRenderWindow(rw);
	rwi->Initialize();
	rwi->Start();

	return 0;
}

3.运行截图