Private Sub Combo1_Click()
    Picture2.Cls
    Picture3.Picture = LoadPicture(App.Path + "\" + Combo1.Text)
    Dim B1  As Double, B2 As Double
    B1 = Me.Picture3.Height / Me.Picture3.Width
    B2 = Me.Picture1.Height / Me.Picture1.Width
    If Me.Picture3.Width <= Me.Picture1.Width And Me.Picture3.Height <= Me.Picture1.Width Then
        Me.Picture2.Width = Me.Picture3.Width
        Me.Picture2.Height = Me.Picture3.Height
        Me.Picture2.Left = (Me.Picture1.Width - Me.Picture3.Width) / 2
        Me.Picture2.Top = (Me.Picture1.Height - Me.Picture3.Height) / 2
    ElseIf Me.Picture3.Width > Me.Picture1.Width Or Me.Picture3.Height > Me.Picture1.Height Then
        If B1 >= B2 Then  '也就是说应该按照高度缩放

            Me.Picture2.Top = 0
            Me.Picture2.Height = Me.Picture1.Height
            Me.Picture2.Width = Me.Picture2.Height / B1
            Me.Picture2.Left = (Me.Picture1.Width - Me.Picture2.Width) / 2

        Else
            Me.Picture2.Left = 0
            Me.Picture2.Width = Me.Picture1.Width
            Me.Picture2.Height = Me.Picture1.Width * B1
            Me.Picture2.Top = (Me.Picture1.Height - Me.Picture2.Height) / 2

        End If
    End If

    Picture2.PaintPicture Picture3.Picture, 0, 0, Picture2.Width, Picture2.Height, 0, 0, Picture3.Width, Picture3.Height

End Sub

Sub YSCCLL(Frm As Form)
    With Frm
        Frm.Picture2.Picture = LoadPicture(App.Path + "\" + Combo1.Text)
        If .Picture2.Height > .Picture1.Height And .Picture2.Width > .Picture1.Width Then
            '图片尺寸高宽均大于图片框的尺寸
            .Picture2.Left = 0
            .Picture2.Top = 0
            '水平滚动条
            With .HScroll1
                .Enabled = True
                .Max = Frm.Picture2.Width - Frm.Picture1.Width
                .LargeChange = .Max / 2
                .Value = .Max / 2
            End With
            '垂直滚动条
            With .VScroll1
                .Enabled = True
                .Max = Frm.Picture2.Height - Frm.Picture1.Height
                .LargeChange = .Max / 2
                .Value = .Max / 2
            End With

        ElseIf .Picture2.Height > .Picture1.Height And .Picture2.Width <= .Picture1.Width Then
            '图片的高度超过图片框的高度
            .Picture2.Left = 0
            .Picture2.Top = 0
            .HScroll1.Enabled = False
            '垂直滚动条
            With .VScroll1
                .Enabled = True
                .Max = Frm.Picture2.Height - Frm.Picture1.Height
                .LargeChange = .Max / 2
                .Value = .Max / 2
            End With
            .Picture2.Left = (.Picture1.Width - Frm.Picture2.Width) / 2
        ElseIf .Picture2.Height <= .Picture1.Height And .Picture2.Width > .Picture1.Width Then
            '图片的宽度超过图片框的宽度
            .Picture2.Left = 0
            .Picture2.Top = 0
            .VScroll1.Enabled = False
            '水平滚动条
            With .HScroll1
                .Enabled = True
                .Max = Frm.Picture2.Width - Frm.Picture1.Width
                .LargeChange = .Max / 2
                .Value = .Max / 2
            End With
            .Picture2.Top = (.Picture1.Height - Frm.Picture2.Height) / 2
        Else
            '图片的尺寸均小于等于图片框的尺寸
            .VScroll1.Enabled = False
            .HScroll1.Enabled = False
            .Picture2.Left = (.Picture1.Width - Frm.Picture2.Width) / 2
            .Picture2.Top = (.Picture1.Height - Frm.Picture2.Height) / 2
        End If
    End With
End Sub