SizePic 说明：可以用于WEB网站图片缩略图的批量处理[1]

昨天网友问我怎样获得图片的缩略图，我说简单，但是他说要保持原来的比例，且缩略图的大小是固定的尺寸，我说要思考一会儿。

我数学憋到极点，哎！但是这个我还是算得来

如图

下面是源代码：
'************************************
'* ---------SizePic------------
'说明：可以用于WEB网站图片缩略图的批量处理
'*支持jpg,bmp,pnp,gif,tif
'* author:wgscd
'* Dte:2005/09/30
'*由于用了异常捕捉try，可能效率得到了限制
'*部分代码许完善
'*QQ:153964481
'**********************************
Public Class Form1
    Inherits System.Windows.Forms.Form

#Region " Windows 窗体设计器生成的代码 "

    Public Sub New()
        MyBase.New()

        '该调用是 Windows 窗体设计器所必需的。
        InitializeComponent()

        '在 InitializeComponent() 调用之后添加任何初始化

    End Sub

    '窗体重写 dispose 以清理组件列表。
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Windows 窗体设计器所必需的
    Private components As System.ComponentModel.IContainer

    '注意: 以下过程是 Windows 窗体设计器所必需的
    '可以使用 Windows 窗体设计器修改此过程。
    '不要使用代码编辑器修改它。
    Friend WithEvents PictureBox1 As System.Windows.Forms.PictureBox
    Friend WithEvents Button1 As System.Windows.Forms.Button
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    Friend WithEvents Button2 As System.Windows.Forms.Button
    Friend WithEvents TextBox2 As System.Windows.Forms.TextBox
    Friend WithEvents Button3 As System.Windows.Forms.Button
    Friend WithEvents Label1 As System.Windows.Forms.Label
    Friend WithEvents Label2 As System.Windows.Forms.Label
    Friend WithEvents NumericUpDown1 As System.Windows.Forms.NumericUpDown
    Friend WithEvents NumericUpDown2 As System.Windows.Forms.NumericUpDown
    Friend WithEvents Label3 As System.Windows.Forms.Label
    Friend WithEvents Label4 As System.Windows.Forms.Label
    Friend WithEvents GroupBox1 As System.Windows.Forms.GroupBox
    Friend WithEvents ProgressBar1 As System.Windows.Forms.ProgressBar
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Dim resources As System.Resources.ResourceManager = New System.Resources.ResourceManager(GetType(Form1))
        Me.PictureBox1 = New System.Windows.Forms.PictureBox
        Me.Button1 = New System.Windows.Forms.Button
        Me.TextBox1 = New System.Windows.Forms.TextBox
        Me.Button2 = New System.Windows.Forms.Button
        Me.TextBox2 = New System.Windows.Forms.TextBox
        Me.Button3 = New System.Windows.Forms.Button
        Me.Label1 = New System.Windows.Forms.Label
        Me.Label2 = New System.Windows.Forms.Label
        Me.NumericUpDown1 = New System.Windows.Forms.NumericUpDown
        Me.NumericUpDown2 = New System.Windows.Forms.NumericUpDown
        Me.Label3 = New System.Windows.Forms.Label
        Me.Label4 = New System.Windows.Forms.Label
        Me.GroupBox1 = New System.Windows.Forms.GroupBox
        Me.ProgressBar1 = New System.Windows.Forms.ProgressBar
        CType(Me.NumericUpDown1, System.ComponentModel.ISupportInitialize).BeginInit()
        CType(Me.NumericUpDown2, System.ComponentModel.ISupportInitialize).BeginInit()
        Me.GroupBox1.SuspendLayout()