c# jpg图片转换成 bmp格式

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

namespace JPGChangeBMP
{
    public partial class Frm_Main : Form
    {
        Bitmap bitmap;
        public Frm_Main（）
        {
            InitializeComponent（）;
        }

        private void buttonOpen_Click（object sender EventArgs e）
        {
            OpenFileDialog openFileDialog = new OpenFileDialog（）;
            openFileDialog.Filter = “*.jpg|*.jpg“;
            openFileDialog.title = “打开图像文件“;
            openFileDialog.Multiselect = false;
            if （openFileDialog.ShowDialog（） == DialogResult.OK）
            {

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----
     目录           0  2011-12-22 23:11  JPGChangeBMP\
     文件         926  2013-05-20 07:14  JPGChangeBMP.sln
     文件       18944  2010-11-04 01:45  JPGChangeBMP.suo
     目录           0  2011-12-22 23:11  JPGChangeBMP\bin\
     目录           0  2013-05-20 07:14  JPGChangeBMP\bin\Debug\
     文件       11776  2013-05-20 07:14  JPGChangeBMP\bin\Debug\JPGChangeBMP.exe
     文件       24064  2013-05-20 07:14  JPGChangeBMP\bin\Debug\JPGChangeBMP.pdb
     文件        4038  2010-07-13 00:24  JPGChangeBMP\Frm_Main.cs
     文件        7110  2010-07-08 21:50  JPGChangeBMP\Frm_Main.designer.cs
     文件        5814  2010-07-08 21:50  JPGChangeBMP\Frm_Main.resx
     文件        4028  2013-05-20 07:14  JPGChangeBMP\JPGChangeBMP.csproj
     目录           0  2011-12-22 23:11  JPGChangeBMP\obj\
     目录           0  2013-05-20 07:14  JPGChangeBMP\obj\Debug\
     文件         789  2013-05-20 07:14  JPGChangeBMP\obj\Debug\DesignTimeResolveAssemblyReferences.cache
     文件        7164  2013-05-20 07:14  JPGChangeBMP\obj\Debug\DesignTimeResolveAssemblyReferencesInput.cache
     文件        3817  2013-05-20 07:14  JPGChangeBMP\obj\Debug\JPGChangeBMP.csproj.FileListAbsolute.txt
     文件         850  2013-05-20 07:14  JPGChangeBMP\obj\Debug\JPGChangeBMP.csproj.GenerateResource.Cache
     文件        1757  2013-05-20 07:14  JPGChangeBMP\obj\Debug\JPGChangeBMP.csprojResolveAssemblyReference.cache
     文件       11776  2013-05-20 07:14  JPGChangeBMP\obj\Debug\JPGChangeBMP.exe
     文件         180  2013-05-20 07:14  JPGChangeBMP\obj\Debug\JPGChangeBMP.Frm_Main.resources
     文件       24064  2013-05-20 07:14  JPGChangeBMP\obj\Debug\JPGChangeBMP.pdb
     文件         180  2013-05-20 07:14  JPGChangeBMP\obj\Debug\JPGChangeBMP.Properties.Resources.resources
     目录           0  2011-12-22 23:11  JPGChangeBMP\obj\Debug\Refactor\
     目录           0  2013-05-20 07:14  JPGChangeBMP\obj\Debug\TempPE\
     文件        4608  2013-05-20 07:14  JPGChangeBMP\obj\Debug\TempPE\Properties.Resources.Designer.cs.dll
     文件         496  2010-07-08 21:50  JPGChangeBMP\Program.cs
     目录           0  2011-12-22 23:11  JPGChangeBMP\Properties\
     文件        1356  2010-07-08 21:49  JPGChangeBMP\Properties\AssemblyInfo.cs
     文件        2864  2013-05-20 07:14  JPGChangeBMP\Properties\Resources.Designer.cs
     文件        5612  2010-07-08 21:49  JPGChangeBMP\Properties\Resources.resx
     文件        1112  2013-05-20 07:14  JPGChangeBMP\Properties\Settings.Designer.cs
............此处省略1个文件信息