VB里怎样在image或picture控件内按比例缩小显示图片

可以用代码实现。
以下代码是我原来做过的实例里剪出来的，你可以参考一下，imgPreview 为Image对象。

Private Type PreviewSize
sngLeft As Single
sngTop As Single
sngWidth As Single
sngHeight As Single
intZoon As Integer
End Type

Private muPreviewSize As PreviewSize
Private Const cmChangeSize = 1.2

'// 缩小
Private Sub Command1_Click()
With muPreviewSize
.intZoon = .intZoon - 1
.sngHeight = .sngHeight / cmChangeSize
.sngWidth = .sngWidth / cmChangeSize

imgPreview.Stretch = True
imgPreview.Move .sngLeft, .sngTop, .sngWidth, .sngHeight

'// 如果已经缩小了9倍则缩小按钮不可用
If .intZoon < -9 Then
Command1.Enabled = False
Command2.Enabled = True
Else
Command2.Enabled = True
End If
End With
End Sub

'// 放大
Private Sub Command2_Click()
With muPreviewSize
.intZoon = .intZoon + 1
.sngHeight = .sngHeight * cmChangeSize