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(Namedpicture2)，一个Command按键)
OptionExplicit
PrivateDeclareFunctionBitBltLib"gdi32"(ByValhDestDCAsLong,ByValxAsLong,ByValyAsLong,ByValnWidthAsLong,ByValnHeightAsLong,ByValhSrcDCAsLong,ByValxSrcAsLong,ByValySrcAsLong,ByValdwRopAsLong)AsLong
PrivateDeclareFunctionCreateCompatibleDCLib"gdi32"(ByValhdcAsLong)AsLong
PrivateDeclareFunctionSelectObjectLib"gdi32"(ByValhdcAsLong,ByValhObjectAsLong)AsLong
PrivateDeclareFunctionDeleteDCLib"gdi32"(ByValhdcAsLong)AsLong
ConstSRCCOPY=&HCC0020
PrivatePicture1AsNewStdPicture

PrivateSubCommand1_Click()
DimiAsLong
DimjAsLong
Dimheight5AsLong,width5AsLong
DimhMemDcAsLong

'stdPicture物件的度量单位是Himetric所以要转换成Pixel
height5=ScaleY(Picture1.Height,vbHimetric,vbPixels)
Ifheight5>Picture2.ScaleHeightThen
height5=Picture2.ScaleHeight
EndIf
width5=ScaleX(Picture1.Width,vbHimetric,vbPixels)
Ifwidth5>Picture2.ScaleWidthThen
width5=Picture2.ScaleWidth
EndIf
'CreateMemoryDC
hMemDc=CreateCompatibleDC(Picture2.hdc)
'将Picture1的BitMap图指定给hMemDc
CallSelectObject(hMemDc,Picture1.Handle)
Fori=height5To1Step-1
CallBitBlt(Picture2.hdc,0,i,width5,1,hMemDc,0,i,SRCCOPY)
Forj=i-1To1Step-1
CallBitBlt(Picture2.hdc,0,j,width5,1,hMemDc,0,i,SRCCOPY)
Nextj
Next
CallDeleteDC(hMemDc)
EndSub

PrivateSubForm_Load()
DimiAsLong
Picture2.ScaleMode=3'设定成Pixel的度量单位
'设定待Display的图
SetPicture1=LoadPicture("c:\windows\素还真.bmp")
'^^^^^^^^^^^^^^^^^^^^^^
'Loadthepicturewewanttoshow
EndSub->