VB保存截图

我发现 用printwindow 截屏后，保存时出错了
代码：
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Private Declare Function PrintWindow Lib "user32" (ByVal SrcHwnd As Long, ByVal DesHDC As Long, ByVal uFlag As Long) As Long
Private Sub Command3_Click()
Picture1.Cls
Call PrintWindow(399528, Picture1.hdc, 0)
End Sub
Private Sub Command4_Click()
SavePicture Picture1.Picture, "c:/tp1.jpg"
End Sub
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大神帮我看看，就是 SavePicture Picture2.Picture, "c:/tp1.jpg" 这里出错了
然后调试界面显示 picture1.picture=0