VTK边缘检测：梯度算子，Sobel算子，Canny算子，Laplace算子

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QFileDialog>
#include <QDebug>
#include <vtkAutoInit.h>
VTK_MODULE_INIT(vtkRenderingOpenGL2)
VTK_MODULE_INIT(vtkInteractionStyle)
#include <vtkSmartPointer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkJPEGReader.h>
#include <vtkImageData.h>
#include <vtkImageLuminance.h>
#include <vtkImageActor.h>
#include <vtkImageThreshold.h>
#include <vtkInteractorStyleImage.h>

namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
private slots:
    void openFileSlot();
private:
    vtkSmartPointer<vtkRenderer>               pSrcGradientRenderer;
    vtkSmartPointer<vtkRenderer>               pGradientRenderer;

    vtkSmartPointer<vtkRenderer>               pSrcSobelRenderer;
    vtkSmartPointer<vtkRenderer>               pSobelXRenderer;
    vtkSmartPointer<vtkRenderer>               pSobelYRenderer;
    vtkSmartPointer<vtkRenderer>               pSobelRenderer;

    vtkSmartPointer<vtkRenderer>               pSrcCandyRenderer;
    vtkSmartPointer<vtkRenderer>               pCandyRenderer;

    vtkSmartPointer<vtkRenderer>               pSrcLaplaceRenderer;
    vtkSmartPointer<vtkRenderer>               pLaplaceRenderer;

    vtkSmartPointer<vtkInteractorStyleImage>   pImageStyle;
    vtkSmartPointer<vtkJPEGReader>             pJpegReader;

    vtkSmartPointer<vtkImageActor>             pSrcGradientImageActor;
    vtkSmartPointer<vtkImageActor>             pGradientImageActor;

    vtkSmartPointer<vtkImageActor>             pSrcSobelImageActor;
    vtkSmartPointer<vtkImageActor>             pSobelXImageActor;
    vtkSmartPointer<vtkImageActor>             pSobelYImageActor;
    vtkSmartPointer<vtkImageActor>             pSobelImageActor;

    vtkSmartPointer<vtkImageActor>             pSrcCandyImageActor;
    vtkSmartPointer<vtkImageActor>             pCandyImageActor;

    vtkSmartPointer<vtkImageActor>             pSrcLaplaceImageActor;
    vtkSmartPointer<vtkImageActor>             pLaplaceImageActor;
private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <vtkImageGradient.h>
#include <vtkImageMagnitude.h>
#include <vtkImageShiftScale.h>
#include <vtkImageSobel2D.h>
#include <vtkImageExtractComponents.h>
#include <vtkImageMathematics.h>
#include <vtkImageLuminance.h>
#include <vtkImageCast.h>
#include <vtkImageGaussianSmooth.h>
#include <vtkImageNonMaximumSuppression.h>
#include <vtkImageConstantPad.h>
#include <vtkImageToStructuredPoints.h>
#include <vtkLinkEdgels.h>
#include <vtkThreshold.h>
#include <vtkGeometryFilter.h>
#include <vtkSubPixelPositionEdgels.h>
#include <vtkStripper.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkProperty.h>
#include <vtkImageLaplacian.h>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    {
        pSrcGradientRenderer         = vtkSmartPointer<vtkRenderer>::New();
        pSrcGradientRenderer->SetBackground(1.0, 0, 0);
        pSrcGradientRenderer->SetViewport(0, 0, 0.5, 0.25);

        pGradientRenderer      = vtkSmartPointer<vtkRenderer>::New();
        pGradientRenderer->SetBackground(1.0, 0, 0);
        pGradientRenderer->SetViewport(0.5, 0, 1.0, 0.25);

    }

    {
        pSrcSobelRenderer = vtkSmartPointer<vtkRenderer>::New();
        pSrcSobelRenderer->SetBackground(0.0, 1.0, 0.0);
        pSrcSobelRenderer->SetViewport(0, 0.25, 0.25, 0.5);

        pSobelXRenderer      = vtkSmartPointer<vtkRenderer>::New();
        pSobelXRenderer->SetBackground(0.0, 1.0, 0.0);
        pSobelXRenderer->SetViewport(0.25, 0.25, 0.5, 0.5);

        pSobelYRenderer      = vtkSmartPointer<vtk