Microsoft KB Archive/141933

{| = HOWTO: VB4: Capture and Print the Screen, a Form, or any Window =
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Last reviewed: March 21, 1997

Article ID: Q141933 The information in this article applies to:
 * Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY
This article shows how to capture any form or window including the screen into a Visual Basic Picture object. Once the on-screen image is captured in the Picture object, it can easily be printed using the PaintPicture method of the Visual Basic Printer object.

MORE INFORMATION
The included example provides several useful routines for capturing images. All of the routines have been written to work under both 16- and 32-bit Windows platforms and they contain full palette support. The routines in the example can:


 * Capture the entire contents of a form
 * Capture the client area of a form
 * Capture the entire screen
 * Capture the active window on the screen
 * Capture any portion of any window given a handle to it
 * Create a Picture object from a bitmap and a palette
 * Print a Picture object as large as possible on the page

Visual Basic 4.0 introduced a new Picture object. The Picture object is actually a standard OLE type and it is documented in the Control Developer's Kit (CDK.) The CDK includes the function OleCreatePictureIndirect which can be used to construct new Picture objects from Visual Basic 4.0. The routine CreateBitmapPicture in the example calls OleCreatePictureIndirect to build a Picture object from a handle to a bitmap and a handle to a palette. If the Picture includes a valid palette, Visual Basic will know to use it when rendering the Picture to the screen or printer. The CreateBitmapPicture routine is used by the CaptureWindow routine to construct Picture objects containing a bitmap of a part or all of a window.

The CaptureWindow routine in the example captures any portion of a window given a window handle. The routine includes several parameters for describing the exact portion of the window to capture. Capture Window works by copying the on-screen image of a window into a new bitmap. It also checks to see if the screen has a palette and if so it makes a copy of it. CaptureWindow then calls CreateBitmapPicture to construct a bitmap from the newly created bitmap and palette.

The CaptureForm, CaptureClient, CaptureScreen, and CaptureActiveWindow routines included in the example all use CaptureWindow to capture specific windows. CaptureForm and CaptureClient both call Capture window and pass it the hWnd property of a Form object. CaptureScreen simply gets the handle to the desk top window and calls CaptureWindow. Similarly, CaptureActiveWindow just gets the window handle of the active window and calls CaptureWindow.

Once the desired image is captured in a Picture object, it is easy to print in Visual Basic 4.0 using the PaintPicture method of the Printer object. The example provides the routine PrintPictureToFitPage that uses the PaintPictureMethod to print the captured images as large as possible in the printable area of the page.

Example
 Start a new project. Form1 is created by default. Place six CommandButtons on the form along the left side. Place one picture box on the form to the right of the buttons.  Put the following code in Form1: '     ' Capture the entire screen Private Sub Command1_Click Set Picture1.Picture = CaptureScreen End Sub ' Capture the entire form including title and border Private Sub Command2_Click Set Picture1.Picture = CaptureForm(Me) End Sub ' Capture the client area of the form Private Sub Command3_Click Set Picture1.Picture = CaptureClient(Me) End Sub ' Capture the active window after two seconds Private Sub Command4_Click MsgBox "Two seconds after you close this dialog " & _ "the active window will be captured." ' Wait for two seconds Dim EndTime As Date EndTime = DateAdd("s", 2, Now) Do Until Now > EndTime DoEvents Loop Set Picture1.Picture = CaptureActiveWindow ' Set focus back to form Me.SetFocus End Sub ' Print the current contents of the picture box Private Sub Command5_Click PrintPictureToFitPage Printer, Picture1.Picture Printer.EndDoc End Sub ' Clear out the picture box Private Sub Command6_Click Set Picture1.Picture = Nothing End Sub ' Initialize the form and controls Private Sub Form_Load Me.Caption = "Capture and Print Example" Command1.Caption = "&Screen" Command2.Caption = "&Form" Command3.Caption = "&Client" Command4.Caption = "&Active" Command5.Caption = "&Print" Command6.Caption = "C&lear" Picture1.AutoSize = True End Sub '  Add a new standard module to the project (module1 by default).  Put the following code in the new module: '     '''      '      ' Visual Basic 4.0 16/32 Capture Routines '     ' This module contains several routines for capturing windows into a      ' picture. All the routines work on both 16 and 32 bit Windows ' platforms. ' The routines also have palette support. '     ' CreateBitmapPicture - Creates a picture object from a bitmap and ' palette ' CaptureWindow - Captures any window given a window handle ' CaptureActiveWindow - Captures the active window on the desktop ' CaptureForm - Captures the entire form ' CaptureClient - Captures the client area of a form ' CaptureScreen - Captures the entire screen ' PrintPictureToFitPage - prints any picture as big as possible on     ' the page '     ' NOTES ' - No error trapping is included in these routines ''' ' Option Explicit Option Base 0 Private Type PALETTEENTRY peRed As Byte peGreen As Byte peBlue As Byte peFlags As Byte End Type Private Type LOGPALETTE palVersion As Integer palNumEntries As Integer palPalEntry(255) As PALETTEENTRY ' Enough for 256 colors End Type Private Type GUID Data1 As Long Data2 As Integer Data3 As Integer Data4(7) As Byte End Type #If Win32 Then 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 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 #ElseIf Win16 Then Private Const RASTERCAPS As Integer = 38 Private Const RC_PALETTE As Integer = &H100 Private Const SIZEPALETTE As Integer = 104 Private Type RECT Left As Integer Top As Integer Right As Integer Bottom As Integer End Type Private Declare Function CreateCompatibleDC Lib "GDI" ( _ ByVal hDC As Integer) As Integer Private Declare Function CreateCompatibleBitmap Lib "GDI" ( _ ByVal hDC As Integer, ByVal nWidth As Integer, _ ByVal nHeight As Integer) As Integer Private Declare Function GetDeviceCaps Lib "GDI" ( _ ByVal hDC As Integer, ByVal iCapabilitiy As Integer) As Integer Private Declare Function GetSystemPaletteEntries Lib "GDI" ( _ ByVal hDC As Integer, ByVal wStartIndex As Integer, _ ByVal wNumEntries As Integer, _ lpPaletteEntries As PALETTEENTRY) As Integer Private Declare Function CreatePalette Lib "GDI" ( _ lpLogPalette As LOGPALETTE) As Integer Private Declare Function SelectObject Lib "GDI" ( _ ByVal hDC As Integer, ByVal hObject As Integer) As Integer Private Declare Function BitBlt Lib "GDI" ( _ ByVal hDCDest As Integer, ByVal XDest As Integer, _ ByVal YDest As Integer, ByVal nWidth As Integer, _ ByVal nHeight As Integer, ByVal hDCSrc As Integer, _ ByVal XSrc As Integer, ByVal YSrc As Integer, _ ByVal dwRop As Long) As Integer Private Declare Function DeleteDC Lib "GDI" ( _ ByVal hDC As Integer) As Integer Private Declare Function GetForegroundWindow Lib "USER" _ Alias "GetActiveWindow"  As Integer Private Declare Function SelectPalette Lib "USER" ( _ ByVal hDC As Integer, ByVal hPalette As Integer, ByVal _ bForceBackground As Integer) As Integer Private Declare Function RealizePalette Lib "USER" ( _ ByVal hDC As Integer) As Integer Private Declare Function GetWindowDC Lib "USER" ( _ ByVal hWnd As Integer) As Integer Private Declare Function GetDC Lib "USER" ( _ ByVal hWnd As Integer) As Integer Private Declare Function GetWindowRect Lib "USER" ( _ ByVal hWnd As Integer, lpRect As RECT) As Integer Private Declare Function ReleaseDC Lib "USER" ( _ ByVal hWnd As Integer, ByVal hDC As Integer) As Integer Private Declare Function GetDesktopWindow Lib "USER"  As Integer Private Type PicBmp Size As Integer Type As Integer hBmp As Integer hPal As Integer Reserved As Integer End Type Private Declare Function OleCreatePictureIndirect _ Lib "oc25.dll" ( PictDesc As PicBmp, RefIID As GUID, _ ByVal fPictureOwnsHandle As Integer, IPic As IPicture) _ As Integer #End If ' ' ' CreateBitmapPicture ' - Creates a bitmap type Picture object from a bitmap and palette ' ' hBmp ' - Handle to a bitmap ' ' hPal ' - Handle to a Palette ' - Can be null if the bitmap doesn't use a palette ' ' Returns ' - Returns a Picture object containing the bitmap ' ' #If Win32 Then Public Function CreateBitmapPicture(ByVal hBmp As Long, _ ByVal hPal As Long) As Picture Dim r As Long #ElseIf Win16 Then Public Function CreateBitmapPicture(ByVal hBmp As Integer, _ ByVal hPal As Integer) As Picture Dim r As Integer #End If Dim Pic As PicBmp ' IPicture requires a reference to "Standard OLE Types" Dim IPic As IPicture Dim IID_IDispatch As GUID ' Fill in with IDispatch Interface ID With IID_IDispatch .Data1 = &H20400 .Data4(0) = &HC0 .Data4(7) = &H46 End With ' Fill Pic with necessary parts With Pic .Size = Len(Pic) ' Length of structure .Type = vbPicTypeBitmap ' Type of Picture (bitmap) .hBmp = hBmp ' Handle to bitmap .hPal = hPal ' Handle to palette (may be null) End With ' Create Picture object r = OleCreatePictureIndirect(Pic, IID_IDispatch, 1, IPic) ' Return the new Picture object Set CreateBitmapPicture = IPic End Function ' ' ' CaptureWindow ' - Captures any portion of a window ' ' hWndSrc ' - Handle to the window to be captured ' ' Client ' - If True CaptureWindow captures from the client area of the ' window ' - If False CaptureWindow captures from the entire window ' ' LeftSrc, TopSrc, WidthSrc, HeightSrc ' - Specify the portion of the window to capture ' - Dimensions need to be specified in pixels ' ' Returns ' - Returns a Picture object containing a bitmap of the specified ' portion of the window that was captured '  ' #If Win32 Then 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 #ElseIf Win16 Then Public Function CaptureWindow(ByVal hWndSrc As Integer, _ ByVal Client As Boolean, ByVal LeftSrc As Integer, _ ByVal TopSrc As Integer, ByVal WidthSrc As Long, _ ByVal HeightSrc As Long) As Picture Dim hDCMemory As Integer Dim hBmp As Integer Dim hBmpPrev As Integer Dim r As Integer Dim hDCSrc As Integer Dim hPal As Integer Dim hPalPrev As Integer Dim RasterCapsScrn As Integer Dim HasPaletteScrn As Integer Dim PaletteSizeScrn As Integer #End If Dim LogPal As LOGPALETTE ' Depending on the value of Client get the proper device context If Client Then hDCSrc = GetDC(hWndSrc) ' Get device context for client area Else hDCSrc = GetWindowDC(hWndSrc) ' Get device context for entire ' window End If ' Create a memory device context for the copy process hDCMemory = CreateCompatibleDC(hDCSrc) ' Create a bitmap and place it in the memory DC hBmp = CreateCompatibleBitmap(hDCSrc, WidthSrc, HeightSrc) hBmpPrev = SelectObject(hDCMemory, hBmp) ' Get screen properties RasterCapsScrn = GetDeviceCaps(hDCSrc, RASTERCAPS) ' Raster 'capabilities HasPaletteScrn = RasterCapsScrn And RC_PALETTE ' Palette 'support PaletteSizeScrn = GetDeviceCaps(hDCSrc, SIZEPALETTE) ' Size of ' palette ' If the screen has a palette make a copy and realize it If HasPaletteScrn And (PaletteSizeScrn = 256) Then ' Create a copy of the system palette LogPal.palVersion = &H300 LogPal.palNumEntries = 256 r = GetSystemPaletteEntries(hDCSrc, 0, 256, _ LogPal.palPalEntry(0)) hPal = CreatePalette(LogPal) ' Select the new palette into the memory DC and realize it hPalPrev = SelectPalette(hDCMemory, hPal, 0) r = RealizePalette(hDCMemory) End If ' Copy the on-screen image into the memory DC r = BitBlt(hDCMemory, 0, 0, WidthSrc, HeightSrc, hDCSrc, _ LeftSrc, TopSrc, vbSrcCopy) ' Remove the new copy of the on-screen image hBmp = SelectObject(hDCMemory, hBmpPrev) ' If the screen has a palette get back the palette that was ' selected in previously If HasPaletteScrn And (PaletteSizeScrn = 256) Then hPal = SelectPalette(hDCMemory, hPalPrev, 0) End If ' Release the device context resources back to the system r = DeleteDC(hDCMemory) r = ReleaseDC(hWndSrc, hDCSrc) ' Call CreateBitmapPicture to create a picture object from the ' bitmap and palette handles. Then return the resulting picture ' object. Set CaptureWindow = CreateBitmapPicture(hBmp, hPal) End Function ' ' ' CaptureScreen ' - Captures the entire screen ' ' Returns ' - Returns a Picture object containing a bitmap of the screen ' ' Public Function CaptureScreen As Picture #If Win32 Then Dim hWndScreen As Long #ElseIf Win16 Then Dim hWndScreen As Integer #End If ' Get a handle to the desktop window hWndScreen = GetDesktopWindow ' Call CaptureWindow to capture the entire desktop give the handle ' and return the resulting Picture object Set CaptureScreen = CaptureWindow(hWndScreen, False, 0, 0, _ Screen.Width \ Screen.TwipsPerPixelX, _ Screen.Height \ Screen.TwipsPerPixelY) End Function ' ' ' CaptureForm ' - Captures an entire form including title bar and border ' ' frmSrc ' - The Form object to capture ' ' Returns ' - Returns a Picture object containing a bitmap of the entire ' form ' ' Public Function CaptureForm(frmSrc As Form) As Picture ' Call CaptureWindow to capture the entire form given it's window ' handle and then return the resulting Picture object Set CaptureForm = CaptureWindow(frmSrc.hWnd, False, 0, 0, _ frmSrc.ScaleX(frmSrc.Width, vbTwips, vbPixels), _ frmSrc.ScaleY(frmSrc.Height, vbTwips, vbPixels)) End Function ' ' ' CaptureClient ' - Captures the client area of a form ' ' frmSrc ' - The Form object to capture ' ' Returns ' - Returns a Picture object containing a bitmap of the form's ' client area ' ' Public Function CaptureClient(frmSrc As Form) As Picture ' Call CaptureWindow to capture the client area of the form given ' it's window handle and return the resulting Picture object Set CaptureClient = CaptureWindow(frmSrc.hWnd, True, 0, 0, _ frmSrc.ScaleX(frmSrc.ScaleWidth, frmSrc.ScaleMode, vbPixels), _ frmSrc.ScaleY(frmSrc.ScaleHeight, frmSrc.ScaleMode, vbPixels)) End Function ' ' ' CaptureActiveWindow ' - Captures the currently active window on the screen ' ' Returns ' - Returns a Picture object containing a bitmap of the active ' window ' ' Public Function CaptureActiveWindow As Picture #If Win32 Then Dim hWndActive As Long Dim r As Long #ElseIf Win16 Then Dim hWndActive As Integer Dim r As Integer #End If Dim RectActive As RECT ' Get a handle to the active/foreground window hWndActive = GetForegroundWindow ' Get the dimensions of the window r = GetWindowRect(hWndActive, RectActive) ' Call CaptureWindow to capture the active window given it's ' handle and return the Resulting Picture object Set CaptureActiveWindow = CaptureWindow(hWndActive, False, 0, 0, _ RectActive.Right - RectActive.Left, _ RectActive.Bottom - RectActive.Top) End Function ' ' ' PrintPictureToFitPage ' - Prints a Picture object as big as possible ' ' Prn ' - Destination Printer object ' ' Pic ' - Source Picture object ' ' Public Sub PrintPictureToFitPage(Prn As Printer, Pic As Picture) Const vbHiMetric As Integer = 8 Dim PicRatio As Double Dim PrnWidth As Double Dim PrnHeight As Double Dim PrnRatio As Double Dim PrnPicWidth As Double Dim PrnPicHeight As Double ' Determine if picture should be printed in landscape or portrait ' and set the orientation If Pic.Height >= Pic.Width Then Prn.Orientation = vbPRORPortrait ' Taller than wide Else Prn.Orientation = vbPRORLandscape ' Wider than tall End If ' Calculate device independent Width to Height ratio for picture PicRatio = Pic.Width / Pic.Height ' Calculate the dimentions of the printable area in HiMetric PrnWidth = Prn.ScaleX(Prn.ScaleWidth, Prn.ScaleMode, vbHiMetric) PrnHeight = Prn.ScaleY(Prn.ScaleHeight, Prn.ScaleMode, vbHiMetric) ' Calculate device independent Width to Height ratio for printer PrnRatio = PrnWidth / PrnHeight ' Scale the output to the printable area If PicRatio >= PrnRatio Then ' Scale picture to fit full width of printable area PrnPicWidth = Prn.ScaleX(PrnWidth, vbHiMetric, Prn.ScaleMode) PrnPicHeight = Prn.ScaleY(PrnWidth / PicRatio, vbHiMetric, _ Prn.ScaleMode) Else ' Scale picture to fit full height of printable area PrnPicHeight = Prn.ScaleY(PrnHeight, vbHiMetric, Prn.ScaleMode) PrnPicWidth = Prn.ScaleX(PrnHeight * PicRatio, vbHiMetric, _ Prn.ScaleMode) End If ' Print the picture using the PaintPicture method Prn.PaintPicture Pic, 0, 0, PrnPicWidth, PrnPicHeight End Sub '  Save the project. Run the project and test. You should be able to capture the form, the form's client area, the screen, and the active window. You will also be able to print any of these.</li></ol>

NOTES: Once you have captured the image you want in a Picture object you can easily place it on the clipboard using the SetData method of the Clipboard object.
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