Screen capture of obscured objects

I need to capture a control that is partially or fully obscured. The resault needs to not have the obscuring control/windows in it.

Code:

+----------------------+ | | | | | | +------------| Object B | | | | | +----------------------+ | Object A | | | +-------------------------+

In my method, the screen capture comes up like:

Code:

+------------| Object B | | | +------------- | Object A | | | +-------------------------+

The method I'm looking for would return this:

Code:

+-------------------------+ | | | | | Object A | | | +-------------------------+

You just need to turn autoredraw on, for that object, that is if youre capturing your own windows.

Not possible AFAIK, the areas behind the windows doesn't exist, they are drawn as soon as the WM_PAINT event is fired for those windows. If you ever noticed one way VB crashes, is that it leaves white areas when you move forms over it.

maybe i can SendMessage the wm_paint event to the control in question, and intercept the drawing commands?

BTW, what does AFAIK mean?

Capture Active Screen

Try this one...
*************************************************
1. Start a new Standard Exe project
2. Add component - Microsoft RichTextBox Control
3. Insert 2 forms - Form1 and Form2
4. In Form1, add one Command Button (Command1)
5. In Form2, add one Rich Text Box component (RichTextBox1)
6. Insert one module (bas). Let the name Module1

'=================================
'Copy & Paste this code to Module1
'=================================
Option Explicit
Option Base 0

'--------------------------------------------------------------------
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'
' 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
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

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

'===============================
'Copy & Paste this code to Form1
'===============================
Private Sub Command1_Click()
Clipboard.Clear
Clipboard.SetData CaptureActiveWindow(), vbCFBitmap
Form2.Show
Unload Me
End Sub

Private Sub Form_Load()
Command1.Caption = "Capture this form to Rich Text Box"
Me.Caption = "Capture Active Screen"
End Sub

'===============================
'Copy & Paste this code to Form2
'===============================
Private Sub Form_Load()
RichTextBox1.Text = ""
Me.Caption = "Nahhhh... you go!!!"
Me.WindowState = 2
RichTextBox1.Top = 135
RichTextBox1.Left = 135
End Sub

Private Sub Form_Resize()
RichTextBox1.Width = 0.9 * Me.Width
RichTextBox1.Height = 0.9 * Me.Height
End Sub

Private Sub RichTextBox1_GotFocus()
SendKeys "^{v}", True
End Sub

WM_PAINT would only update the area that is exposed, AFAIK means As Far As I Know, you know, i've tried this myself, even changing the look of a window but it seems like you can't, In Windowblinds they subclassed for WM_PAINT and drawed the custom borders everytime the it exposed, so the only way out is to put the form in foreground and capture it.

as far as i know bitblt and getdc's and stuff only hold display information therefore whatever is displayed is all your going to get... but the data for what to display MUST be someplace by accessing that you could most likely get the image you need I would like to see it happen also but im not that great w/ that stuff :(

Quote:

Originally posted by vinny
as far as i know bitblt and getdc's and stuff only hold display information therefore whatever is displayed is all your going to get... but the data for what to display MUST be someplace by accessing that you could most likely get the image you need I would like to see it happen also but im not that great w/ that stuff :(

Custom drawn controls might have a double buffer, but that is upto the owner.. there's no generic way of knowing, its stuck up inside windowproc and theres no way of telling what else is drawn..

anyway getwindowprocess might be able to at least pick up text drawn on the window if you find the right location?

im trying to do this with an applet window

actually how about this..
i know i can bitblt a invisible picture box.. ive done it in games
how about making the window invisible then bitblting it
maybe w/ showwindow or some other method... think that would work

Well did it? :D

You could maybe get the window you want to capture. Then crawl up the hierarchy calling MoveWindow for every window you come upon to move it to the front of the z-order. Maybe make the windows all topmost for the moment you capture them.

Then update the window to force redrawing and you should be fine.

Dear agent

sorry i dont know then answer but i have my own question
how do you omit objectb?
i have the same project as yours.
but i want to omit or hide every window that are over my active window .
thanks anyway

oh this is from such a long time ago. never was solved.

New idea. use LockWindowUpdate(GetDesktopWindow) on the screen's hwnd, set control's parent to screen and make it topmost, tell it to redraw, capture it, reset it's parent, and LoickWindowUpdate(0)

never tried it, but it may work

thanks

thanks for your reply.
what i want is somthing different.
i want if object a has intersection with object b then intersection part showed black.like application sharing programs.is it possible or not?
thanks anyway.

Re: thanks

Quote:

Posted by vvampirevv
thanks for your reply.
what i want is somthing different.
i want if object a has intersection with object b then intersection part showed black.like application sharing programs.is it possible or not?
thanks anyway.

If I am understanding you right then wouldn't it just be a case of capturing the area as normal then find the insterestion area and Blt a black box over it? ;)

thanks electroman

the problem is how can i find intersection part and how can i feel it black!!!!!!
thanks anyway

If your just using normal VB controls then it would be possible using the Left, Top, Width & Height propertys of the controls. Mind if you don't want to think up some collision code for it then You could create a RECt for each of the Controls then use the IntersectRect() API ;)
VB Code:
Private Declare Function IntersectRect Lib "user32" (lpDestRect As RECT, lpSrc1Rect As RECT, lpSrc2Rect As RECT) As Long
The RECT returned from the APi would then beused to Blt a black box over the area. How this would be done all depends on how you are capturing the original image and how it is stored ;).