用ImagXpress控件画矩形图的问题(高手帮忙啊!)

[zhangtao_smt]

我在ImagXpress的控件画矩形图,在ImagXpress1.DrawMode 设置为 PEN_Xor但是在MouseMove时
却始终擦不掉以前所画的内容代码如下:
Option Explicit
Dim x0, y0, xnow, ynow As Long
Dim down As Boolean
Private Sub ImagXpress1_MouseDown(Button As Integer, Shift As Integer, x As Single, y As Single)
down = True
x0 = ImagXpress1.DIBXPos: y0 = ImagXpress1.DIBYPos
xnow = ImagXpress1.DIBXPos: ynow = ImagXpress1.DIBYPos
ImagXpress1.DrawMode = PEN_Xor
End Sub
Private Sub ImagXpress1_MouseMove(Button As Integer, Shift As Integer, x As Single, y As Single)
If down = True And Button <> 0 Then

ImagXpress1.DrawLine x0, y0, xnow, ynow, QBColor(15), True, False
ImagXpress1.DrawLine x0, y0, ImagXpress1.DIBXPos, ImagXpress1.DIBYPos, QBColor(15), True, False
xnow = ImagXpress1.DIBXPos: ynow = ImagXpress1.DIBYPos
End If
End Sub
Private Sub ImagXpress1_MouseUp(Button As Integer, Shift As Integer, x As Single, y As Single)
down = False
ImagXpress1.DrawLine x0, y0, xnow, ynow, ImagXpress1.BackColor, True, False
ImagXpress1.DrawMode = PEN_CopyPen
ImagXpress1.DrawLine x0, y0, xnow, ynow, vbRed, True, False
End Sub
在画的时候总是会留下痕迹.那位高手过来帮帮忙啊!