大家知道在VB下利用API函数Bitblt可以将屏幕或者窗口上的图象拷贝到VB 中的PictureBox对象中，但是如果简单的利用PictureBox的SavePicture函数来保存图象，会发现什么也保存不了。这篇文章就是介绍如何捕获并利用Windows下的OLE API函数保存图象。
首先来看源程序，首先建立一个新的工程文件，然后在Form1中加入5个CommandButton对象和一个PictureBox对象，然后在Form1中加入以下代码：Option Explicit Option Base 0
Private Type PALETTEENTRY
peRed As Byte
peGreen As Byte
ahb
peBlue As Byte
peFlags As Byte
End Type
Private Type LOGPALETTE
palVersion As Integer
palNumEntries As Integer
palPalEntry(255) As PALETTEENTRY
End Type
Private Type GUID
Data1 As Long
Data2 As Integer
Data3 As Integer
Data4(7) As Byte
ISO项目管理
End Type
Private Const RASTERCAPS As Long = 38
Private Const RC_PALETTE As Long = &H100
Private Const SIZEPALETTE As Long = 104
Private Type RECT
Left As Long
Top As Long
Right As Long
Bottom As Long
End Type
Private Declare Function CreateCompatibleDC Lib "GDI32" (ByVal hDC As Long) As Long
神州奥美Private Declare Function CreateCompatibleBitmap Lib "GDI32" (ByVal hDC As Long, _
ByVal nWidth As Long, ByVal nHeight As Long) As Long
Private Declare Function GetDeviceCaps Lib "GDI32" (ByVal hDC As Long, ByVal _
iCapabilitiy As Long) As Long
Private Declare Function GetSystemPaletteEntries Lib "GDI32" (ByVal hDC As Long, _
ByVal wStartIndex As Long, ByVal wNumEntries As Long, lpPaletteEntries _
As PALETTEENTRY) As Long
Private Declare Function CreatePalette Lib "GDI32" (lpLogPalette As LOGPALETTE) _
As Long
Private Declare Function SelectObject Lib "GDI32" (ByVal hDC As Long, ByVal hObject _
As Long) As Long
Private Declare Function BitBlt Lib "GDI32" (ByVal hDCDest As Long, ByVal XDest As _
Long, ByVal YDest As Long, ByVal nWidth As Long, ByVal nHeight As Long, _
ByVal hDCSrc As Long, ByVal XSrc As Long, ByVal YSrc As Long, ByVal dwRop _
As Long) As Long
Private Declare Function DeleteDC Lib "GDI32" (ByVal hDC As Long) As Long Private Declare Function GetForegroundWindow Lib "USER32" () As Long Private Declare Function SelectPalette Lib "GDI32" (ByVal hDC As Long, ByVal hPalette _
As Long, ByVal bForceBackground As Long) As Long
Private Declare Function RealizePalette Lib "GDI32" (ByVal hDC As Long) As Long
Private Declare Function GetWindowDC Lib "USER32" (ByVal hWnd As Long) As Long
Private Declare Function GetDC Lib "USER32" (ByVal hWnd As Long) As Long Private Declare Function GetWindowRect Lib "USER32" (ByVal hWnd As Long, lpRect As _
RECT) As Long
Private Declare Function ReleaseDC Lib "USER32" (ByVal hWnd As Long, ByVal hDC As _
Long) As Long
Private Declare Function GetDesktopWindow Lib "USER32" () As Long
Private Type PicBmp
Size As Long
Type As Long
hBmp As Long
hPal As Long
Reserved As Long
End Type
Private Declare Function OleCreatePictureIndirect Lib "olepro32.dll" (PicDesc As _
PicBmp, RefIID As GUID, ByVal fPictureOwnsHandle As Long, IPic As IPicture) As Long
'捕捉整个屏幕
Private Sub Command1_Click()
Set Picture1.Picture = CaptureScreen()
End Sub
'在两秒钟后捕捉当前的活动窗口
Private Sub Command2_Click()
MsgBox "当你关闭这个对话框两秒钟之后程序会捕捉处于活动状态的窗口."
'等待两秒钟
Dim EndTime As Date
EndTime = DateAdd("s", 2, Now)
Do Until Now > EndTime
DoEvents
Loop
Set Picture1.Picture = CaptureActiveWindow()
Me.SetFocus
End Sub
Private Sub Command3_Click()
Set Picture1.Picture = Nothing
End Sub
Public Function CreateBitmapPicture(ByVal hBmp As Long, ByVal hPal As Long) As Picture
弥撒曲
Dim r As Long
Dim Pic As PicBmp
Dim IPic As IPicture
Dim IID_IDispatch As GUID
'填充IDispatch界面
With IID_IDispatch
.Data1 = &H20400
.Data4(0) = &HC0
.Data4(7) = &H46
End With
'填充Pic
With Pic
.Size = Len(Pic) ' Pic结构长度
.Type = vbPicTypeBitmap ' 图象类型
.hBmp = hBmp ' 位图句柄
.hPal = hPal ' 调板句柄
End With
'建立Picture图象
r = OleCreatePictureIndirect(Pic, IID_IDispatch, 1, IPic)
'返回Picture对象
Set CreateBitmapPicture = IPic
北京市国有土地上房屋征收与补偿实施意见End Function
Public Function CaptureWindow(ByVal hWndSrc As Long, ByVal Client As Boolean, ByVal _
LeftSrc As Long, ByVal TopSrc As Long, ByVal WidthSrc As Long, ByVal HeightSrc _
As Long) As Picture
Dim hDCMemory As Long
Dim hBmp As Long
Dim hBmpPrev As Long
Dim r As Long
Dim hDCSrc As Long
Dim hPal As Long
Dim hPalPrev As Long
Dim RasterCapsScrn As Long
Dim HasPaletteScrn As Long
Dim PaletteSizeScrn As Long
Dim LogPal As LOGPALETTE
If Client Then
hDCSrc = GetDC(hWndSrc)
Else
hDCSrc = GetWindowDC(hWndSrc)
End If
hDCMemory = CreateCompatibleDC(hDCSrc)
hBmp = CreateCompatibleBitmap(hDCSrc, WidthSrc, HeightSrc)
hBmpPrev = SelectObject(hDCMemory, hBmp)
'获得屏幕属性
RasterCapsScrn = GetDeviceCaps(hDCSrc, RASTERCAPS)
HasPaletteScrn = RasterCapsScrn And RC_PALETTE
PaletteSizeScrn = GetDeviceCaps(hDCSrc, SIZEPALETTE)
'如果屏幕对象有调板则获得屏幕调板
If HasPaletteScrn And (PaletteSizeScrn = 256) Then
'建立屏幕调板的拷贝
LogPal.palVersion = &H300
LogPal.palNumEntries = 256
爱的拐点r = GetSystemPaletteEntries(hDCSrc, 0, 256,
LogPal.palPalEntry(0))
hPal = CreatePalette(LogPal)
'将新建立的调板选如建立的内存绘图句柄中
hPalPrev = SelectPalette(hDCMemory, hPal, 0)
r = RealizePalette(hDCMemory)
End If
'拷贝图象
r = BitBlt(hDCMemory, 0, 0, WidthSrc, HeightSrc, hDCSrc, LeftSrc, TopSrc, vbSrcCopy)
hBmp = SelectObject(hDCMemory, hBmpPrev)
If HasPaletteScrn And (PaletteSizeScrn = 256) Then
hPal = SelectPalette(hDCMemory, hPalPrev, 0)
End If
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