使用 System.Drawing 绘制圆圈

Question

我有这段代码可以绘制一个矩形（我正在尝试重新制作 MS Paint）

 case "Rectangle":
               if (tempDraw != null)
                {
                    tempDraw = (Bitmap)snapshot.Clone();
                    Graphics g = Graphics.FromImage(tempDraw);
                    Pen myPen = new Pen(foreColor, lineWidth);
                    g.DrawRectangle(myPen, x1, y1, x2-x1, y2-y1);
                    myPen.Dispose();
                    e.Graphics.DrawImageUnscaled(tempDraw, 0, 0);
                    g.Dispose();
                }

但是如果我想画一个圆，会发生什么变化呢？

g.DrawRectangle(myPen, x1, y1, x2-x1, y2-y1);

Answer 1

没有DrawCircle 方法；请改用DrawEllipse。我有一个带有方便图形扩展方法的静态类。以下是绘制和填充圆圈。它们是 DrawEllipse 和 FillEllipse 的包装器：

public static class GraphicsExtensions
{
    public static void DrawCircle(this Graphics g, Pen pen,
                                  float centerX, float centerY, float radius)
    {
        g.DrawEllipse(pen, centerX - radius, centerY - radius,
                      radius + radius, radius + radius);
    }

    public static void FillCircle(this Graphics g, Brush brush,
                                  float centerX, float centerY, float radius)
    {
        g.FillEllipse(brush, centerX - radius, centerY - radius,
                      radius + radius, radius + radius);
    }
}

你可以这样称呼他们：

g.FillCircle(myBrush, centerX, centerY, radius);
g.DrawCircle(myPen, centerX, centerY, radius);

Answer 2

改用DrawEllipse 方法。

Answer 3

如果您想使用 GDI+ 绘制圆，则需要使用 DrawEllipse。

这里有一个例子：http://www.websupergoo.com/helpig6net/source/3-examples/9-drawgdi.htm

Answer 4

你应该使用DrawEllipse:

//
// Summary:
//     Draws an ellipse defined by a bounding rectangle specified by coordinates
//     for the upper-left corner of the rectangle, a height, and a width.
//
// Parameters:
//   pen:
//     System.Drawing.Pen that determines the color, width,
//      and style of the ellipse.
//
//   x:
//     The x-coordinate of the upper-left corner of the bounding rectangle that
//     defines the ellipse.
//
//   y:
//     The y-coordinate of the upper-left corner of the bounding rectangle that
//     defines the ellipse.
//
//   width:
//     Width of the bounding rectangle that defines the ellipse.
//
//   height:
//     Height of the bounding rectangle that defines the ellipse.
//
// Exceptions:
//   System.ArgumentNullException:
//     pen is null.
public void DrawEllipse(Pen pen, int x, int y, int width, int height);

Answer 5

如果你想在按钮上画圆圈，那么这段代码可能会被完整使用。 否则，如果您想在其他控件上画一个圆圈，只需更改控件的名称和事件。像这里调用事件按钮。如果要在组框中绘制此圆圈，请调用 Groupbox 事件。 问候

    public Form1()
    {
        InitializeComponent();

    }

    private void Form1_Load(object sender, EventArgs e)
    {
        this.button1.Location = new Point(108, 12);
       // this.Paint += new PaintEventHandler(Form1_Paint);
        this.button1.Paint += new PaintEventHandler(button1_Paint);
    }
    void button1_Paint(object sender, PaintEventArgs e)
    {
        Graphics g = this.button1.CreateGraphics();
        Pen pen = new Pen(Color.Red);
        g.DrawEllipse(pen, 10, 10, 20, 20);

    }





}

Answer 6

使用此代码，您可以轻松地画一个圆... 我的朋友，C# 很棒而且很简单

public partial class Form1 : Form
{


public Form1()
    {
        InitializeComponent();
    }

  private void button1_Click(object sender, EventArgs e)
    {
        Graphics myGraphics = base.CreateGraphics();
        Pen myPen = new Pen(Color.Red);
        SolidBrush mySolidBrush = new SolidBrush(Color.Red);
        myGraphics.DrawEllipse(myPen, 50, 50, 150, 150);
    }
 }

Answer 7

     private void DrawEllipseRectangle(PaintEventArgs e)
        {
            Pen p = new Pen(Color.Black, 3);
            Rectangle r = new Rectangle(100, 100, 100, 100);
            e.Graphics.DrawEllipse(p, r);
        }
     private void Form1_Paint(object sender, PaintEventArgs e)
        {
            DrawEllipseRectangle(e);
        }

Answer 8

PictureBox circle = new PictureBox();
circle.Paint += new PaintEventHandler(circle_Paint);        

void circle_Paint(object sender, PaintEventArgs e)
        {
            e.Graphics.DrawEllipse(Pens.Red, 0, 0, 30, 30);
        }