c# - 刷新两次picturebox显示错误图像

Question

我编写了一个VideoBox类，该类显示使用opencv从视频文件或网络摄像头捕获的图像，这是我在c++中的代码，我需要一个固定大小的框，因此我覆盖了最小值和最大值

public ref class VideoBox : public System::Windows::Forms::PictureBox
{
public:
    VideoBox();
    ~VideoBox();

    bool capture()
    {
        cv::Mat cur_frame;
        bool r = maintracker.capture(cur_frame);

        if(!r) return r;

        imshow("debug window", cur_frame);
        this->Image  = gcnew System::Drawing::Bitmap(cur_frame.cols, cur_frame.rows, cur_frame.step, System::Drawing::Imaging::PixelFormat::Format24bppRgb, (System::IntPtr)cur_frame.ptr());
        this->Refresh();

        return true;
    }

    ....

    virtual property System::Drawing::Size MinimumSize {
        System::Drawing::Size get() override { return m_desiredSize; } 
        void set(System::Drawing::Size) override { } 
    }
    virtual property System::Drawing::Size MaximumSize {
        System::Drawing::Size get() override { return m_desiredSize; }  
        void set(System::Drawing::Size) override { } 
    }

protected:
/*  virtual void OnPaint(System::Windows::Forms::PaintEventArgs^ pe) override
    {
        PictureBox::OnPaint(pe);
    }*/

private:
    System::Drawing::Size m_desiredSize;
};

这是我的C#类从VideoBox继承

 public class Video : VideoBox
{
    public enum DrawMode { DRAW_H_LINE, DRAW_V_LINE, DRAW_RECT, NONE };
    public enum ShowMode { SHOW_USER_RECTS, SHOW_USER_LINES, HIDE_ALL, SHOW_ALL };

    public Video()
    {
        b_drawrect = b_drawhline = b_drawvline = false;
        lstBrush = new HatchBrush(HatchStyle.BackwardDiagonal, Color.Green, Color.Transparent);

        cTimer = new Timer();
        cTimer.Interval = 100; // msec for change frame in video mode
        cTimer.Tick += new EventHandler(cTimer_Tick);

        // if you uncomment this you can see your image on design mode :D            
        //setCaptureVideo();

        m_drMode = DrawMode.DRAW_RECT;
        m_userRects = new List<Rectangle>();
    }

    public void setCaptureVideo()
    { 
        ...
    }

    public void startVideo() { cTimer.Start(); }
    public void stopVideo() { cTimer.Stop(); }

    private void cTimer_Tick(object sender, EventArgs e)
    {
        capture();
    }

    //protected override void OnPaint(PaintEventArgs e)
    //{
    //    base.OnPaint(e);

    //    Graphics g = e.Graphics;
    //    if (m_insertRect.Width > 0 && b_drawrect)
    //    {
    //        Pen mP = new Pen(Color.Green);
    //        g.DrawRectangle(mP, m_insertRect);
    //    }

    //    if (m_shMode == ShowMode.SHOW_USER_RECTS || m_shMode == ShowMode.SHOW_ALL)
    //    {
    //        Font drawFont = new Font("Arial",8 );
    //        SolidBrush drawBrush = new SolidBrush(Color.Red);

    //        // Set format of string.
    //        StringFormat drawFormat = new StringFormat();
    //        if(m_userRects.Count > 0)
    //        {
    //            int c=1;
    //            foreach(Rectangle rect in m_userRects)
    //            {
    //                g.FillRectangle(lstBrush, rect);
    //                g.DrawString(c.ToString(), drawFont, drawBrush, rect.Location, drawFormat);
    //                c++;
    //            }
    //        }
    //    }
    //}

    protected override void OnMouseMove(MouseEventArgs e)
    {
        base.OnMouseMove(e);

        if (e.Button == System.Windows.Forms.MouseButtons.Left)
        {
            if (m_drMode == DrawMode.DRAW_RECT && !m_firstp.IsEmpty)
            {
                b_drawrect = true;

                float x = m_firstp.X < e.X ? m_firstp.X : e.X;
                float y = m_firstp.Y < e.Y ? m_firstp.Y : e.Y;
                float w = Math.Abs(m_firstp.X - e.X);
                float h = Math.Abs(m_firstp.Y - e.Y);

                m_insertRect = new Rectangle((int)x, (int)y, (int)w, (int)h);

                if (!cTimer.Enabled)
                    this.Refresh();
            }
        }

        if(m_drMode == DrawMode.DRAW_H_LINE && !m_firstp.IsEmpty)
        {
            m_hlinep = e.Location;
            b_drawhline = true;
            if(!cTimer.Enabled)
                this.Refresh();
        }
        else if (m_drMode == DrawMode.DRAW_V_LINE && !m_firstp.IsEmpty)
        {
            m_vlinep = e.Location;
            b_drawvline = true;

            if (!cTimer.Enabled)
                this.Refresh();
        }
    }

    protected override void OnMouseDown(MouseEventArgs e)
    {
        base.OnMouseDown(e);

        if (b_drawvline)
        {
            b_drawvline = false;
            m_vlinep = e.Location;
            m_drMode = DrawMode.NONE;
        }
        else if (b_drawhline)
        {
            b_drawhline = false;
            m_hlinep = e.Location;
            m_drMode = DrawMode.NONE;
        }
        else
            m_firstp = e.Location;
    }

    protected override void OnMouseUp(MouseEventArgs e)
    {
        base.OnMouseUp(e);
        if (m_drMode == DrawMode.DRAW_RECT)
        {
            if (b_drawrect)
            {
                m_userRects.Add(m_insertRect);
                b_drawrect = false;
                if (!cTimer.Enabled)
                    this.Refresh();
            }
        }
    }

    // private members
    private List<Rectangle> m_userRects;
    private Timer cTimer;
    private PointF m_firstp;
    private PointF m_hlinep, m_vlinep;
    private Rectangle m_insertRect;
    private bool b_drawrect, b_drawhline, b_drawvline;
    private HatchBrush lstBrush;

    private ShowMode m_shMode;
    private DrawMode m_drMode;
}

如果我多次调整窗体的大小，VideoBox将显示PictureBox的ErrorImage

如果启用cTimer时刷新视频框，则再次显示ErrorImage

imshow可以正常工作

您认为问题出在哪里？

Answer 1

首先，请注意:opencv(主要基于RAII)和托管c++不能一起使用。

您可以在捕获功能中分配本地Mat:

bool capture()
{
    cv::Mat cur_frame;
    ...

一旦它超出范围(离开capture()时)，并且您的ImageBox留下无效/悬空的指针，它将释放/使它的数据指针无效。

因此，您必须在整个程序运行期间保持cv::Mat cur_frame处于 Activity 状态，在此情况下，它变得非常难看:

public:

    cv::Mat *cur_frame; // yep, a bloody *pointer*, as stupid managed c++ can't do RAII...

    VideoBox() 
    {
        cur_frame = new Mat();
    }
    ~VideoBox() 
    {
        delete cur_frame;
    }

    bool capture()
    {
        bool r = maintracker.capture( *cur_frame ); // deref

        if(!r) return r;

        imshow("debug window", *cur_frame);
        this->Image  = gcnew System::Drawing::Bitmap(cur_frame->cols, cur_frame->rows, cur_frame->step, System::Drawing::Imaging::PixelFormat::Format24bppRgb, (System::IntPtr)cur_frame->ptr());
        this->Refresh();

        return true;
    }