C# 把图片显示成椭圆形状

实例如图所示

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

namespace ShowImageByEllipse
{
    public partial class Form1 : Form
    {
        public Form1（）
        {
            InitializeComponent（）;
        }
        private Bitmap SourceBitmap;
        private Bitmap MyBitmap;
        private void button2_Click（object sender EventArgs e）
        {
            //打开图像文件
            OpenFileDialog openFileDialog = new OpenFileDialog（）;
            openFileDialog.Filter = “图像文件（JPeg Gif Bmp etc.）|*.jpg;*.jpeg;*.gif;*.bmp;*.tif; *.tiff; *.png| JPeg 图像文件（*.jpg;*.jpeg）|*.jpg;*.jpeg |GIF 图像文件（*.gif）|*.gif |BMP图像文件（*.bmp）|*.bmp|Tiff图像文件（*.tif;*.tiff）|*.tif;*.tiff|Png图像文件（*.png）| *.png |所有文件（*.*）|*.*“;
            if （openFileDialog.ShowDialog（） == DialogResult.OK）
            {
                //得到原始大小的图像
                SourceBitmap = new Bitmap（openFileD

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----
     目录           0  2011-12-22 23:11  ShowImageByEllipse\
     文件         944  2013-05-28 21:49  ShowImageByEllipse.sln
     文件       27136  2010-11-04 01:59  ShowImageByEllipse.suo
     目录           0  2011-12-22 23:11  ShowImageByEllipse\bin\
     目录           0  2013-05-28 21:49  ShowImageByEllipse\bin\Debug\
     文件       10240  2013-05-28 21:49  ShowImageByEllipse\bin\Debug\ShowImageByEllipse.exe
     文件       24064  2013-05-28 21:49  ShowImageByEllipse\bin\Debug\ShowImageByEllipse.pdb
     文件        1741  2010-07-13 17:05  ShowImageByEllipse\Form1.cs
     文件        4382  2010-07-08 22:28  ShowImageByEllipse\Form1.designer.cs
     文件        5814  2010-07-08 22:28  ShowImageByEllipse\Form1.resx
     目录           0  2011-12-22 23:11  ShowImageByEllipse\obj\
     目录           0  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\
     文件        7200  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\DesignTimeResolveAssemblyReferencesInput.cache
     文件        4228  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\ShowImageByEllipse.csproj.FileListAbsolute.txt
     文件         847  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\ShowImageByEllipse.csproj.GenerateResource.Cache
     文件        1757  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\ShowImageByEllipse.csprojResolveAssemblyReference.cache
     文件       10240  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\ShowImageByEllipse.exe
     文件         180  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\ShowImageByEllipse.Form1.resources
     文件       24064  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\ShowImageByEllipse.pdb
     文件         180  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\ShowImageByEllipse.Properties.Resources.resources
     目录           0  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\TempPE\
     文件        4608  2013-05-28 21:49  ShowImageByEllipse\obj\Debug\TempPE\Properties.Resources.Designer.cs.dll
     文件         499  2010-07-08 22:26  ShowImageByEllipse\Program.cs
     目录           0  2011-12-22 23:11  ShowImageByEllipse\Properties\
     文件        1368  2010-07-08 22:26  ShowImageByEllipse\Properties\AssemblyInfo.cs
     文件        2876  2013-05-28 21:49  ShowImageByEllipse\Properties\Resources.Designer.cs
     文件        5612  2010-07-08 22:26  ShowImageByEllipse\Properties\Resources.resx
     文件        1118  2013-05-28 21:49  ShowImageByEllipse\Properties\Settings.Designer.cs
     文件         249  2010-07-08 22:26  ShowImageByEllipse\Properties\Settings.settings
     文件        4025  2013-05-28 21:49  ShowImageByEllipse\ShowImageByEllipse.csproj