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雨滴式的显示图片

? 本范例是以一个stdPicture物件来存图形，之後於PictureBox中以特殊效果来显示。
　　因为我们想显示的只有一个图，所以不想多用另一个PictureBox来存原始图，而後 再画到另一个PictureBox上，那只有用StdPicture物件来取代PictureBox(存来源图) ，但是BitBlt这个绘图函式需来源与目的的hDc，而StdPicture物件没有hDc，它只有 一个Handle值，以本例来说，这Handle值便是图形的hBitmap值。所以我们只好使用MemoryDC的方式来做，产生一个MemoryDc後将BitMap图放於其上，之後便可以使用BitBlt来绘图了。

需求一个PictureBox( Named picture2)，一个Command按键)
Option Explicit
Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, _
ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, _
ByVal nHeight As Long, ByVal hSrcDC As Long, _
ByVal xSrc As Long, ByVal ySrc As Long, _
ByVal dwRop As Long) As Long
Private Declare Function CreateCompatibleDC Lib "gdi32" _
(ByVal hdc As Long) As Long
Private Declare Function SelectObject Lib "gdi32" _
(ByVal hdc As Long, ByVal hObject As Long) As Long
Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long
Const SRCCOPY = &HCC0020
Private Picture1 As New StdPicture

Private Sub Command1_Click()
Dim i As Long
Dim j As Long
Dim height5 As Long, width5 As Long
Dim hMemDc As Long

stdPicture物件的度量单位是Himetric所以要转换成Pixel
height5 = ScaleY(Picture1.Height, vbHimetric, vbPixels)
If height5 $#@62; Picture2.ScaleHeight Then
height5 = Picture2.ScaleHeight
End If
width5 = ScaleX(Picture1.Width, vbHimetric, vbPixels)
If width5 $#@62; Picture2.ScaleWidth Then
width5 = Picture2.ScaleWidth
End If
Create Memory DC
hMemDc = CreateCompatibleDC(Picture2.hdc)
将Picture1的BitMap图指定给hMemDc
Call SelectObject(hMemDc, Picture1.Handle)
For i = height5 To 1 Step -1
Call BitBlt(Picture2.hdc, 0, i, width5, 1, _
hMemDc, 0, i, SRCCOPY)
For j = i - 1 To Step -1
Call BitBlt(Picture2.hdc, 0, j, width5, 1, _
hMemDc, 0, i, SRCCOPY)
Next j
Next
Call DeleteDC(hMemDc)
End Sub

Private Sub Form_Load()
Dim i As Long
Picture2.ScaleMode = 3 设定成Pixel的度量单位
设定待Display的图
Set Picture1 = LoadPicture("c:\windows\素还真.bmp")
^^^^^^^^^^^^^^^^^^^^^^
Load the picture we want to show
End Sub