在图片框中的椭圆内锁定鼠标光标

Question

我正在制作一个自定义颜色选择器，并且我有一个hsv色轮作为图片框中的图像。我正在努力让它在我的鼠标按住时保持在圆圈内。我累了Cursor.Clip但它只使用矩形。

在这张照片中提请一个细黑椭圆围绕车轮。

 Size mySize = new Size(348, 348); 
     Point myloc = new Point(26, 26); 
     Rectangle rec = new Rectangle(); 
     rec.Size = mySize; 
     rec.Location = myloc; 


     Graphics.FromImage(pictureBox1.Image).DrawEllipse(Pens.Black, rec); 
     this.pictureBox1.Refresh(); 

Answer 1

样本解决方案，不是最好的，但工程。 当然，MouseMove事件并不适合您的目的，您应该将WinAPI附加到全局鼠标移动处理上，但这是另一项任务。

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 
using System.Windows.Forms; 

namespace WinForm 
{ 
    public partial class frmMain : Form 
    { 
     private Point centerPoint;    // circle center point 
     private double radius;     // circle radius (R) 
     private double radius2;     // R^2 

     /// <summary> 
     /// form constructor 
     /// </summary> 
     public frmMain() 
     { 
      InitializeComponent(); 

      this.Size = new Size(640, 480); 
      this.Load += delegate 
      { 
       PictureBox pb = new PictureBox(); 

       int size = Math.Min(this.ClientSize.Width, this.ClientSize.Height) - 20; 

       pb.Location = new Point((this.ClientSize.Width - size)/2, (this.ClientSize.Height - size)/2); 
       pb.Size = new Size(size, size); 
       pb.Paint += (s, e) => 
       { 
        var g = e.Graphics; 
        var rect = new Rectangle(Point.Empty, pb.Size); 

        g.FillEllipse(Brushes.ForestGreen, rect); 
        g.DrawEllipse(Pens.Navy, rect); 

        // base cursor clip 
        this.Cursor = new Cursor(Cursor.Current.Handle); 
        Cursor.Position = new Point(Cursor.Position.X - 50, Cursor.Position.Y - 50); 
        Cursor.Clip = pb.RectangleToScreen(rect); 
       }; 

       this.Controls.Add(pb); 

       // setup circle parameters 
       centerPoint = new Point(pb.Left + pb.Width/2, pb.Top + pb.Height/2); 
       radius = (double)size * 0.5; 
       radius2 = radius * radius; 


       // bind to events 
       pb.MouseMove += Mouse_Move; 
       this.MouseMove += Mouse_Move; 
      }; 
     } 

     private void Mouse_Move(object sender, MouseEventArgs e) 
     { 
      // client mouse point 
      var point = this.PointToClient(((Control)sender).PointToScreen(e.Location)); 

      // circle center point 
      double cx = centerPoint.X; 
      double cy = centerPoint.Y; 

      // circle center offset 
      double sx = point.X - cx; 
      double sy = point.Y - cy; 

      // direction angle 
      double alpha = Math.Atan2(-sy, sx); 
      this.Text = string.Format("{0} {1} {2:0.00} rad, {3:0} degrees", sx, sy, alpha, 180.0 * alpha/Math.PI); 

      // range to center 
      double range = sx * sx + sy * sy; 
      if (range > radius2) 
      { 
       int px = (int)Math.Round(cx + Math.Cos(alpha) * radius); 
       int py = (int)Math.Round(cy - Math.Sin(alpha) * radius); 
       Cursor.Position = this.PointToScreen(new Point(px, py)); 
      } 
     } 
    } 
}