把图象文件转换成XML格式文件

利用.NET 框架下的FromBase64String和ToBase64String方法可以很容易地实现图象文件和XML文件的互换。这样可以轻易解决以XML格式保存图片的问题。代码如下：   

  Private MyFile As String = ""
  Private MyFileExt As String = ""
  Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
    Handles Button2.Click
    Dim pic As String
    Dim MyXml As System.Xml.XmlDocument = New System.Xml.XmlDocument()
    MyXml.Load("c:\MyPhoto.xml")
    Dim picNode As System.Xml.XmlNode
    picNode = MyXml.SelectSingleNode("/pic/photo")
    pic = picNode.InnerText
    Dim memoryStream As System.IO.MemoryStream
    memoryStream = New System.IO.MemoryStream(Convert.FromBase64String(pic))
    Me.PictureBox1.Image = New System.Drawing.Bitmap(memoryStream)
    memoryStream.Close()
  End Sub

  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
    Handles Button1.Click
    If MyFile = "" Then
      MessageBox.Show("请选择一个图片！", "错误", MessageBoxButtons.OK, MessageBoxIcon.Warning)
      Exit Sub
    End If
    Dim MyImg As System.Drawing.Image = MyImg.FromFile(MyFile)
    Dim memoryStream As System.IO.MemoryStream = New System.IO.MemoryStream()
    MyImg.Save(memoryStream, GetImageType(MyFileExt))
    Dim b() As Byte
    b = memoryStream.GetBuffer()
    Dim pic As String = Convert.ToBase64String(b)
    memoryStream.Close()
    Dim MyXml As System.Xml.XmlDocument = New System.Xml.XmlDocument()
    MyXml.LoadXml("<pic><name>孟宪会</name><photo>" + pic + "</photo></pic>")
    MyXml.Save("c:\MyPhoto.xml")
    Label1.Text = "文件被保存到了：" + Microsoft.VisualBasic.ChrW(13) + "c:\MyPhoto.xml"
  End Sub

  Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
    Handles Button3.Click
    Dim openFileDialog1 As New OpenFileDialog()
    openFileDialog1.InitialDirectory = "c:\"
    openFileDialog1.Filter = "PNG(*.png)|*.png|Gif(*.gif)|*.gif|Jpg(*.jpg)|*.jpg|所有图象文件(*.*)|*.*"
    openFileDialog1.FilterIndex = 2
    openFileDialog1.RestoreDirectory = True
    If openFileDialog1.ShowDialog() = DialogResult.OK Then
      MyFile = openFileDialog1.FileName()
      MyFileExt = MyFile.Substring(MyFile.LastIndexOf(".") + 1)
    End If
  End Sub

  Public Function GetImageType(ByVal str As String) As System.Drawing.Imaging.ImageFormat
    Select Case str.ToLower()
      Case "jpg"
        Return System.Drawing.Imaging.ImageFormat.Jpeg
      Case "gif"
        Return System.Drawing.Imaging.ImageFormat.Gif
      Case "tiff"
        Return System.Drawing.Imaging.ImageFormat.Tiff()
      Case "icon"
        Return System.Drawing.Imaging.ImageFormat.Icon
      Case "image/png"
        Return System.Drawing.Imaging.ImageFormat.Png
      Case Else
        Return System.Drawing.Imaging.ImageFormat.MemoryBmp
    End Select
  End Function