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.Width\Screen.TwipsPerPixelX
height5=Screen.Height\Screen.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。