在鼠标拖动C#上绘图时形状不可见

Posted 2023-02-16

【中文标题】在鼠标拖动C#上绘图时形状不可见

【英文标题】：Shapes not visible while drawing on mouse drag C#

【发布时间】：2015-09-22 03:09:33

【问题描述】：

我是一名新开发人员。我正在尝试制作一个简单的程序，我们可以在其中绘制多个形状，例如矩形、椭圆、直线等。我现在面临的问题是，当我单击鼠标并拖动以在 mouseDown 和 mouseMove 事件上绘制我无法看到形状。仅当我离开鼠标时，该形状才会出现在图片框上。 我希望形状在用户绘制时出现并随鼠标移动，就像在 Microsoft 的绘图应用程序中一样。 我在绘图时尝试使用 Refresh() 函数，但它删除了已经在图片框中绘制的旧形状。 下面是我正在使用的代码。需要一些建议。

bool draw = false;
    bool isMouseDown = false;
    int x, y, lx, ly = 0;
    Item currItem;
    Pen pen = new Pen(Color.Red,1);

    public enum Item
     
        Rectangle, Ellipse, Line, Pencil, Eraser
    

    private void btnROIDraw_Click(object sender, EventArgs e)
    
        if (menuStripRoi.Visible == false)
        
            menuStripRoi.Visible = true;
        
        else
        
            menuStripRoi.Visible = false;
            draw = false;
        
    

    private void pictureBoxROI_MouseDown(object sender, MouseEventArgs e)
    
        x = e.X;
        y = e.Y;
        isMouseDown = true;
        //draw = true;
    
    private void pictureBoxROI_MouseUp(object sender, MouseEventArgs e)
    
        lx = e.X;
        ly = e.Y;

        if (draw)
        
            Graphics g = pictureBoxROI.CreateGraphics();
            switch (currItem)
            
                case Item.Rectangle:
                    g.DrawRectangle(pen, x, y, e.X - x, e.Y - y);
                    break;
                case Item.Ellipse:
                    g.DrawEllipse(pen, x, y, e.X - x, e.Y - y);
                    break;
                case Item.Line:
                    g.DrawLine(pen, x, y, e.X, e.Y);
                    break;
            
            g.Dispose();
        
        isMouseDown = false;

    

    private void pictureBoxROI_MouseMove(object sender, MouseEventArgs e)
    
        if (isMouseDown)
        
            if (draw)
            
                Graphics g = pictureBoxROI.CreateGraphics();
                switch (currItem)
                
                    case Item.Pencil:
                        g.FillEllipse(new SolidBrush(Color.Red), e.X - x + x, e.Y - y + y, 2, 2);
                        break;
                    case Item.Eraser:
                        g.FillEllipse(new SolidBrush(pictureBoxROI.BackColor), e.X - x + x, e.Y - y + y, 20, 20);
                        break;
                
                g.Dispose();
            
        
    

    private void pictureBoxROI_Paint(object sender, PaintEventArgs e)
    

    
    private void clearToolStripMenuItem_Click(object sender, EventArgs e)
    
        pictureBoxROI.Refresh();
    

    private void rectangleToolStripMenuItem_Click(object sender, EventArgs e)
    
        currItem = Item.Rectangle;
        draw = true;
    

    private void ellipseToolStripMenuItem_Click(object sender, EventArgs e)
    
        currItem = Item.Ellipse;
        draw = true;
    

    private void lineToolStripMenuItem_Click(object sender, EventArgs e)
    
        currItem = Item.Line;
        draw = true;
    

    private void pencilToolStripMenuItem_Click(object sender, EventArgs e)
    
        currItem = Item.Pencil;
        draw = true;
    

    private void eracerToolStripMenuItem_Click(object sender, EventArgs e)
    
        currItem = Item.Eraser;
        draw = true;
    

    private void newToolStripMenuItem_Click(object sender, EventArgs e)
    
        pictureBoxROI.Refresh();
        pictureBoxROI.Image = null;
    

    private void openToolStripMenuItem_Click(object sender, EventArgs e)
    
        OpenFileDialog o = new OpenFileDialog();
        o.Filter = "Png files|*.png|jpeg files|*jpg|bitmaps|*.bmp";
        if (o.ShowDialog() == System.Windows.Forms.DialogResult.OK)
        
            pictureBoxROI.Image = (Image)Image.FromFile(o.FileName).Clone();
        
    

    private void saveToolStripMenuItem_Click(object sender, EventArgs e)
    
        Bitmap bmp = new Bitmap(pictureBoxROI.Width, pictureBoxROI.Height);
        Graphics g = Graphics.FromImage(bmp);
        Rectangle rect = pictureBoxROI.RectangleToScreen(pictureBoxROI.ClientRectangle);
        g.CopyFromScreen(rect.Location, Point.Empty, pictureBoxROI.Size);
        g.Dispose();
        SaveFileDialog s = new SaveFileDialog();
        s.Filter = "Png files|*.png|jpeg files|*jpg|bitmaps|*.bmp";
        if (s.ShowDialog() == System.Windows.Forms.DialogResult.OK)
        
            if (File.Exists(s.FileName))
            
                File.Delete(s.FileName);
            
            if (s.FileName.Contains(".jpg"))
            
                bmp.Save(s.FileName, ImageFormat.Jpeg);
            
            else if (s.FileName.Contains(".png"))
            
                bmp.Save(s.FileName, ImageFormat.Png);
            
            else if (s.FileName.Contains(".bmp"))
            
                bmp.Save(s.FileName, ImageFormat.Bmp);
            
        
    

【参考方案1】：

找到了我的问题的解决方案。 本文详细解释了有关使用 GDI+ 进行绘图的所有内容。值得一看 http://www.codeproject.com/Articles/17893/Extensions-to-DrawTools