Question

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

namespace Test
{
    public partial class Form1 : Form
    {
        int circleDiameter;

        public Form1()
        {
            InitializeComponent();

            circleDiameter = 100;
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            Point CenterPoint = new Point()
            {
                X = this.ClientRectangle.Width / 2,
                Y = this.ClientRectangle.Height / 2
            };
            Point topLeft = new Point()
            {
                X = (this.ClientRectangle.Width - circleDiameter) / 2,
                Y = (this.ClientRectangle.Height - circleDiameter) / 2
            };
            Point topRight = new Point()
            {
                X = (this.ClientRectangle.Width + circleDiameter) / 2,
                Y = (this.ClientRectangle.Height - circleDiameter) / 2
            };
            Point bottomLeft = new Point()
            {
                X = (this.ClientRectangle.Width - circleDiameter) / 2,
                Y = (this.ClientRectangle.Height + circleDiameter) / 2
            };
            Point bottomRight = new Point()
            {
                X = (this.ClientRectangle.Width + circleDiameter) / 2,
                Y = (this.ClientRectangle.Height + circleDiameter) / 2
            };

            e.Graphics.DrawEllipse(Pens.Red,topLeft.X, topLeft.Y, circleDiameter, circleDiameter);
            e.Graphics.DrawLine(Pens.Red, CenterPoint, topLeft);
            e.Graphics.DrawLine(Pens.Red, CenterPoint, topRight);
            e.Graphics.DrawLine(Pens.Red, CenterPoint, bottomLeft);
            e.Graphics.DrawLine(Pens.Red, CenterPoint, bottomRight); 
        }
    }
}

结果是在Form的中心和X内部的圆圈，但是X离开了圆圈边界，我想要在topLeft topRight bottomLeft bottomRight内部的X得到精确到圆的边界。我怎么修理它？

在它之前是e.Graphics.DrawEllipse它是e.Graphics.DrawRectangle并且没关系但是一旦我将它改为DrawEllipse，X里面就越过了圆边界。

Answer 1

我已经做了一段时间了。您可以使用Cos和Sin来计算圆上的点，如下所示：

    private Point GetPointOnCircle(Point centre, double angle, double diameter)
    {
        return new Point((int)(Math.Cos(angle) * diameter) + centre.X, (int)(Math.Sin(angle) * diameter) + centre.Y);
    }

我不记得cos是x还是y但是它并不重要只是改变你认为是圆圈上的0度点。无论如何，因为你的角度总是45度，cos（45）和sin（45）是相同的你只需要乘以你的距离0.70710678118654752440084436210485或者有人说1 / sqrt（2）

例如

        Point topRight = new Point()
        {
            X = (this.ClientRectangle.Width + (int)(circleDiameter * 0.70710678118654752440084436210485)) / 2,
            Y = (this.ClientRectangle.Height - (int)(circleDiameter * 0.70710678118654752440084436210485)) / 2
        };

Answer 2

如果我们减少圆直径以激发像circleDiameter = 68这样的值，它将正常工作并进入圆圈

int circleDiameter;

public form()
{
  InitializeComponent();

  circleDiameter = 68;
}

我画了一个圆圈，在里面我从中心画了4条线但是线条离开了圆圈边界为什么？

2 个答案: