C#绘图，如何实现鼠标点击在坐标系中绘制椭圆

[babalala2020]

]

如·这个图中的左图这样的效果

[assky124]

鼠标按下pt1 弹起pt2 然后控件的绘图列表加入一个椭圆对象，请求刷新界面 控件OnPaint 绘制就完了，你有啥不会的？

[babalala2020]

你好你好，是这样，我之前没有接触过C#，老师突然丢给一个项目让做，也没有头绪，所以在论坛问问大神，你说的意思我没有太懂可以再讲讲嘛

[平底锅锅锅]

DrawEllipse

[desperaso]

临时写的，参考着看

public class PanelEx : Panel
        {
            public PanelEx()
            {
                SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.OptimizedDoubleBuffer | ControlStyles.ResizeRedraw | ControlStyles.SupportsTransparentBackColor | ControlStyles.UserPaint, true);
                UpdateStyles();
            }
        }

        PanelEx panel;
        private Point origin = new Point(0,0);
        private Point distance = new Point(0, 0);
        private bool is_press = false;
        private Pen pen = new Pen(Color.SteelBlue, 2);

        public Form1()
        {
            InitializeComponent();

            panel = new PanelEx()
            {
                Size = new Size(600, 600),
                Location = new Point(5, 5),
                BackColor = Color.White
            };
            panel.Paint += Panel_Paint;
            panel.MouseUp += Panel_MouseUp;
            panel.MouseDown += Panel_MouseDown;
            panel.MouseMove += Panel_MouseMove;
            this.Controls.Add(panel);
        }

        private void Panel_Paint(object sender, PaintEventArgs e)
        {
            e.Graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
            e.Graphics.DrawEllipse(pen, origin.X, origin.Y,distance.X,distance.Y);
        }

        private void Panel_MouseUp(object sender, MouseEventArgs e)
        {
            if (is_press)
            {
                Bitmap bmp = new Bitmap(panel.Width, panel.Height);
                using (Graphics gr = Graphics.FromImage(bmp))
                {
                    var screen = panel.PointToScreen(new Point(0, 0));
                    gr.CopyFromScreen(new Point(screen.X, screen.Y), Point.Empty, panel.Size);
                }
                panel.BackgroundImage = bmp;
                is_press = false;
            }
        }

        private void Panel_MouseDown(object sender, MouseEventArgs e)
        {
            is_press = true;
            origin = e.Location;
        }

        private void Panel_MouseMove(object sender, MouseEventArgs e)
        {
            if (is_press)
            {
                distance = e.Location;
                panel.Invalidate();
            }
        }