如何在 WinForm 中选择形状

Question

我有一个 c# WinForm 项目，其中包含以下代码来绘制矩形和椭圆形：

public partial class Form1 : Form
{

    List<Rectangle> _rectangles = new();
    List<Rectangle> _ellipses = new();
    Rectangle _rectInProgress;

    bool DrawingRectangle = false;
    bool DrawingEllipse = false;

    public Form1()
    {
        InitializeComponent();
        DoubleBuffered = true;
    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void Form1_MouseDown(object sender, MouseEventArgs e)
    {
        if (DrawingRectangle || DrawingEllipse)
        {
            _rectInProgress = new Rectangle(e.Location, new Size());
        }
    }

    private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
        if (MouseButtons == MouseButtons.Left && (DrawingRectangle || DrawingEllipse))
        {
            _rectInProgress.Width = e.Location.X - _rectInProgress.X;
            _rectInProgress.Height = e.Location.Y - _rectInProgress.Y;
            Invalidate();
        }
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
        if (DrawingRectangle)
        {
            _rectangles.Add(_rectInProgress);
            Invalidate();
        }
        else if (DrawingEllipse)
        {
            _ellipses.Add(_rectInProgress);
            Invalidate();
        }
    }

    private void Form1_Paint(object sender, PaintEventArgs e)
    {

        if (_rectangles.Any())
        {
            e.Graphics.DrawRectangles(new Pen(Color.Blue, 3), _rectangles.ToArray());
        }
        if (_ellipses.Any())
        {
            foreach (var ell in _ellipses)
            {
                e.Graphics.DrawEllipse(new Pen(Color.Blue, 3), ell);
            }
        }
        if (MouseButtons == MouseButtons.Left)
        {
            if (DrawingEllipse)
            {
                e.Graphics.DrawEllipse(new Pen(Color.Red, 3), _rectInProgress);
            }
            else if (DrawingRectangle)
            {
                e.Graphics.DrawRectangle(new Pen(Color.Red, 3), _rectInProgress);
            }
        }
    }

    private void button1_Click(object sender, EventArgs e)
    {
        DrawingRectangle = !DrawingRectangle;
        DrawingEllipse = false;
    }

    private void button2_Click(object sender, EventArgs e)
    {
        DrawingEllipse = !DrawingEllipse;
        DrawingRectangle = false;
    }
}

下一步是使形状可选择，以便可以调整它们的大小。我对这种事情很陌生，所以我不知道从哪里开始。我在互联网上找到了很多示例，但它们都有一个共同点：它们检查光标是否在形状内单击。我需要检查光标是否单击了形状（边框）。

有人对如何进行有任何建议吗？预先感谢！

Answer 1

一种不错的方法是将绘制的矩形或椭圆形的

GraphicsPath

转换为分配给控件的Region。当您执行此操作时，除了图形路径之外，该控件实际上“不存在”。当您单击边框时，与单击控件相同，而当您单击内部时，则不同。

这里有两个可以通过单击边框来调整大小的控件示例，但在这个非常基本的演示中，大小只能从右下角增加或减小。而且，人们可能希望为鼠标单击保持一个计时器，并将其切换到“移动”而不是“调整大小”。不管怎样，这给了你一些可以尝试的东西。

---

矩形

class RectangleControl : Control
{
    public RectangleControl()
    {
        MouseDown += (sender, e) =>
        {
            _isResizing = true;
            _mouseDownPosition = e.Location;
            _mouseDownSize = Size;
        };
        MouseUp += (sender, e) => _isResizing = false;
        MouseEnter += (sender, e) => Cursor = Cursors.Cross;
        MouseLeave += (sender, e) => Cursor = Cursors.Default;
        MouseMove += (sender, e) =>
        {
            if (_isResizing && e.Button == MouseButtons.Left)
            {
                int deltaX = e.Location.X - _mouseDownPosition.X;
                int deltaY = e.Location.Y - _mouseDownPosition.Y;
                var newSize = new Size(
                    _mouseDownSize.Width + deltaX,
                    _mouseDownSize.Height + deltaY);
                Size = newSize;
            }
        };
        SizeChanged += (sender, e) =>
        {
            GraphicsPath path = new GraphicsPath();
            path.AddRectangle(new Rectangle(0, 0, Width, Height));
            Region region = new Region(path);
            Rectangle inflatedRect = new Rectangle(
                BorderWidth, 
                BorderWidth, 
                Width - (BorderWidth * 2), 
                Height - (BorderWidth * 2));
            region.Exclude(inflatedRect);
            Region = region;
        };
    }
    private Point _mouseDownPosition;
    private Size  _mouseDownSize;
    bool _isResizing = default;
    public int BorderWidth { get; set; } = 4;
}

---

椭圆

class EllipseControl : Control
{
    public EllipseControl()
    {
        MouseDown += (sender, e) =>
        {
            _isResizing = true;
            _mouseDownPosition = e.Location;
            _mouseDownSize = Size;
        };
        MouseUp += (sender, e) => _isResizing = false;
        MouseEnter += (sender, e) => Cursor = Cursors.Cross;
        MouseLeave += (sender, e) => Cursor = Cursors.Default;
        MouseMove += (sender, e) =>
        {
            if (_isResizing && e.Button == MouseButtons.Left)
            {
                int deltaX = e.Location.X - _mouseDownPosition.X;
                int deltaY = e.Location.Y - _mouseDownPosition.Y;
                var newSize = new Size(
                    _mouseDownSize.Width + deltaX,
                    _mouseDownSize.Height + deltaY);
                Size = newSize;
            }
        };
        SizeChanged += (sender, e) =>
        {
            GraphicsPath path = new GraphicsPath();
            path.AddEllipse(new Rectangle(0, 0, Width, Height));
            Region region = new Region(path);
            GraphicsPath innerPath = new GraphicsPath();
            innerPath.AddEllipse(
                BorderWidth, 
                BorderWidth, 
                Width - (BorderWidth * 2), 
                Height - (BorderWidth * 2));
            region.Exclude(innerPath);
            Region = region;
        };
    }
    private Point _mouseDownPosition;
    private Size _mouseDownSize;
    bool _isResizing = default;
    public float BorderWidth { get; set; } = 4;
}

---

主窗体

public partial class MainForm : Form
{
    Rectangle _rectInProgress;
    public MainForm()
    {
        InitializeComponent();
        DoubleBuffered = true;
    }
    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        if (MouseButtons == MouseButtons.Left && _isDrawing)
        {
            if(radioButtonRectangle.Checked) 
            {
                using (var pen = new Pen(Brushes.Red, 4F))
                {
                    e.Graphics.DrawRectangle(pen, _rectInProgress);
                }
            }
            else
            {
                using (var pen = new Pen(Brushes.Red, 4F))
                {
                    e.Graphics.DrawEllipse(pen, _rectInProgress);
                }
            }
        }
    }
    protected override void OnMouseDown(MouseEventArgs e)
    {
        base.OnMouseDown(e);
        _isDrawing = true;
        _rectInProgress = new Rectangle(e.Location, new Size());
    }
    protected override void OnMouseMove(MouseEventArgs e)
    {
        base.OnMouseMove(e);
        if (MouseButtons == MouseButtons.Left)
        {
            _rectInProgress.Width = e.Location.X - _rectInProgress.X;
            _rectInProgress.Height = e.Location.Y - _rectInProgress.Y;
            Invalidate();
        }
    }
    protected override void OnMouseUp(MouseEventArgs e)
    {
        base.OnMouseUp(e);
        _isDrawing = false;
        Invalidate();
        Control control;
        if (radioButtonRectangle.Checked)
        {
            control = new RectangleControl
            {
                Location = _rectInProgress.Location,
                Size = _rectInProgress.Size,
                BackColor = Color.Blue,
            };
        }
        else
        {
            control = new EllipseControl
            {
                Location = _rectInProgress.Location,
                Size = _rectInProgress.Size,
                BackColor = Color.Green,
            };
        }
        Controls.Add(control);
    }
    bool _isDrawing = false;
}