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; using System.Drawing.Imaging; using System.IO; namespace WindowsFormsApplication51 {   public partial class Form1 : Form   {     public Form1()     {       InitializeComponent();     }     string filename = "";//文件名     //文件菜單下的“打開”按鈕     private void menuOpen_Click(object sender, EventArgs e)     {       OpenFileDialog of = new OpenFileDialog();       of.Title = "打開文件";       of.Filter = "圖像文件|*.bmp;*.gif;*.jpg;*.png";       if (of.ShowDialog() == DialogResult.OK)       {         filename = of.FileName;         pictureBox1.Image = Image.FromFile(filename);         pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;       }     }     //“轉換格式”按鈕     private void menuConvert_Click(object sender, EventArgs e)     {         ImageFormat[] format = { ImageFormat.Bmp, ImageFormat.Gif, ImageFormat.Jpeg, ImageFormat.Png };       //ImageFormat是using System.Drawing.Imaging;下的方法，用來指定文件的格式       Image image = Image.FromFile(filename);       SaveFileDialog sf = new SaveFileDialog();       sf.InitialDirectory = Path.GetDirectoryName(filename);//system.io下的path里的GetDirectoryName()方法可以返回指定路徑字符串的目錄信息       sf.FileName = Path.GetFileNameWithoutExtension(filename);//返回不具有擴展名的指定路徑字符串的文件名       sf.Filter = "位圖(*.bmp)|*.bmp|交換圖像格式(*.gif)|*.gif|聯合圖像專家組(*.jpg)|*.jpg;*.jpeg|可移植網絡圖形(*.png)|*.png";       if (sf.ShowDialog() == DialogResult.OK)       {         image.Save(sf.FileName, format[sf.FilterIndex - 1]);//選擇下拉表的第一個，則對應數組format[0]         MessageBox.Show("格式轉換成功", "消息");       }       else       {         MessageBox.Show("格式轉換不成功", "消息");       }     }   } }