关于明暗的问题
我看到很多网站在输入密码的时候,整个屏幕都暗下来了,请问这样的效果是如何实现的呢?请提供方法或者思路,谢谢

[解决办法]
是你用的VISTA系统的缘故吧
[解决办法]
一个picturebox，两个按钮

Option Explicit

Private Type RECT
Left As Long
Top As Long
Right As Long
Bottom As Long
End Type

Private Declare Function GetDC Lib "user32 " (ByVal hwnd As Long) As Long
Private Declare Function ReleaseDC Lib "user32 " (ByVal hwnd As Long, ByVal hdc As Long) As Long
Private Declare Function CreatePatternBrush Lib "gdi32 " (ByVal hBitmap As Long) As Long
Private Declare Function PatBlt Lib "gdi32 " (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal dwRop As Long) As Long
Private Declare Function DeleteObject Lib "gdi32 " (ByVal hObject As Long) As Long
Private Declare Function CreateBitmap Lib "gdi32 " (ByVal nWidth As Long, ByVal nHeight As Long, ByVal nPlanes As Long, ByVal nBitCount As Long, lpBits As Any) As Long
Private Declare Function SelectObject Lib "gdi32 " (ByVal hdc As Long, ByVal hObject As Long) As Long
Private Declare Function InvalidateRect Lib "user32 " (ByVal hwnd As Long, ByVal lpRect As Long, ByVal bErase As Long) As Long

Private bybits(1 To 16) As Byte
Private hBitmap As Long, hBrush As Long
Private hDesktopWnd As Long
'将图变暗，如同待关机一般
Private Sub Command1_Click()
Dim rop As Long, res As Long
Dim hdc5 As Long, width5 As Long, height5 As Long
'如果只要让Picture1有效果将底下叁行unMark取代 hdc5, width5, height5叁个值
'hdc5 = Picture1.hdc
'width5 = Picture1.ScaleWidth
'height5 = Picture1.ScaleHeight

'底下叁行设定整个萤幕都暗下来
hdc5 = GetDC(0)
width5 = Screen.Width \ Screen.TwipsPerPixelX
height5 = Screen.Height \ Screen.TwipsPerPixelY

rop = &HA000C9 '与原图做and运算
Call SelectObject(hdc5, hBrush)
res = PatBlt(hdc5, 0, 0, width5, height5, rop)
Call DeleteObject(hBrush)
'如果只暗picture1则底下这一行要mark起来
res = ReleaseDC(0, hdc5)
End Sub
'回复原本的画面
Private Sub Command2_Click()
Dim aa As Long
'如果只暗picture1则底下这一行要unMark起来
'Picture1.Refresh

'如果只暗picture1则底下这一行要mark起来
aa = InvalidateRect(0, 0, 1)
End Sub

Private Sub Form_Load()
Dim ary
Dim i As Long
ary = Array(&H55, &H0, &HAA, &H0, _
&H55, &H0, &HAA, &H0, _
&H55, &H0, &HAA, &H0, _
&H55, &H0, &HAA, &H0)
For i = 1 To 16
bybits(i) = ary(i - 1)
Next i
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
End Sub