利用VB产生屏幕变暗的效果

1.在Form1中加入两个CommandButton和一个PictureBox.

2.在Form1的代码窗口中添加以下代码：
　　PrivateTypeRECT
　　LeftAsLong
　　TopAsLong
　　RightAsLong
　　BottomAsLong
　　EndType

PrivateDeclareFunctionGetDCLib"user32"(ByValhwndAsLong)AsLong
　　PrivateDeclareFunctionReleaseDCLib"user32"(ByValhwndAsLong,ByValhdcAsLong)AsLong
　　PrivateDeclareFunctionCreatePatternBrushLib"gdi32"(ByValhBitmapAsLong)AsLong
　　PrivateDeclareFunctionPatBltLib"gdi32"(ByValhdcAsLong,ByValxAsLong,ByValyAsLong,ByValnWidthAsLong,ByValnHeightAsLong,ByValdwRopAsLong)AsLong
　　PrivateDeclareFunctionDeleteObjectLib"gdi32"(ByValhObjectAsLong)AsLong
　　PrivateDeclareFunctionCreateBitmapLib"gdi32"(ByValnWidthAsLong,ByValnHeightAsLong,ByValnPlanesAsLong,ByValnBitCountAsLong,lpBitsAsAny)AsLong
　　PrivateDeclareFunctionSelectObjectLib"gdi32"(ByValhdcAsLong,ByValhObjectAsLong)AsLong
　　PrivateDeclareFunctionInvalidateRectLib"user32"(ByValhwndAsLong,ByVallpRectAsLong,ByValbEraseAsLong)AsLong
　　Privatebybits(1To16)AsByte
　　PrivatehBitmapAsLong,hBrushAsLong
　　PrivatehDesktopWndAsLong

PrivateSubCommand1_Click()
　　DimropAsLong,resAsLong
　　Dimhdc5AsLong,width5AsLong,height5AsLong
　　hdc5=GetDC(0)
　　width5=Screen.WidthScreen.TwipsPerPixelX
　　height5=Screen.HeightScreen.TwipsPerPixelY
　　rop=&HA000C9
　　CallSelectObject(hdc5,hBrush)
　　res=PatBlt(hdc5,0,0,width5,height5,rop)
　　CallDeleteObject(hBrush)
　　res=ReleaseDC(0,hdc5)
　　EndSub

PrivateSubCommand2_Click()
　　DimaaAsLong
　　aa=InvalidateRect(0,0,1)
　　EndSub
　　PrivateSubForm_Load()
　　Dimary
　　DimiAsLong
　　ary=Array(&H55,&H0,&HAA,&H0,_
　　&H55,&H0,&HAA,&H0,_
　　&H55,&H0,&HAA,&H0,_
　　&H55,&H0,&HAA,&H0)
　　Fori=1To16
　　bybits(i)=ary(i-1)
　　Nexti
　　hBitmap=CreateBitmap(8,8,1,1,bybits(1))
　　hBrush=CreatePatternBrush(hBitmap)
　　Picture1.ForeColor=RGB(0,0,0)
　　Picture1.BackColor=RGB(255,255,255)
　　Picture1.ScaleMode=3
　　EndSub

运行程序，按Command1就可以使屏幕暗下来，按Command2恢复。