Solved

How to Capture Screen ?

Posted on 1998-11-19
6
474 Views
Last Modified: 2013-11-20
Dear experts

I'm using VC++5.0 in WindowNT4.0 SP 3.
I'd like to capture the screen image programatically.
I have to save the certain area which has associated memory DC to 24 bit BMP file on any VGA color depth.
i.e. if my app run on non-true-color VGA environment, memoryDC must be changed and saved as 24 bit type.
For this, I tried as following :
 - CreateCompatibleBitmap(pMemDC,...)
 - Get 24 bit bitmap data with GetDIBits(hBitmap, ..).
But I always get empty data buffer. i.e. '0'.

Following is source code of my app.
--------
CRect rtWnd;
GetDlgItem(IDC_FRAME1)->GetClientRect(rtWnd);

CDC* pFrameWndDC;

BITMAPINFOHEADER      BmpInfoHdr;

BmpInfoHdr.biSize = sizeof(BITMAPINFOHEADER);
BmpInfoHdr.biWidth = rtWnd.Width();
BmpInfoHdr.biHeight = rtWnd.Height();
BmpInfoHdr.biPlanes = 1;
BmpInfoHdr.biBitCount = 24;
BmpInfoHdr.biCompression = BI_RGB;
BmpInfoHdr.biSizeImage = 0;
BmpInfoHdr.biXPelsPerMeter = 0;
BmpInfoHdr.biYPelsPerMeter = 0;
BmpInfoHdr.biClrUsed = 0;
BmpInfoHdr.biClrImportant = 0;

HDC hDC;
CBitmap* pBMP;
HBITMAP hBMP;

void*   pBitmapBuff = calloc((((rtWnd.Width()*3)+3)/4)*4 * rtWnd.Height() * 3, 1); // 24 Bit
      
int nTotlaFrameCount = m_lstMemDC.GetCount();

POSITION pos = m_lstMemDC.GetHeadPosition();

for(int i=0; i<nTotlaFrameCount; i++)
{
    pFrameWndDC = GetFrameDC(i);
            
    hDC = pFrameWndDC->GetSafeHdc();
    pBMP = new CBitmap;
    pBMP->CreateCompatibleBitmap(pFrameWndDC,
           (((rtWnd.Width()*3)+3)/4)*4, rtWnd.Height());
    hBMP = (HBITMAP) pBMP->GetSafeHandle();

    GetDIBits( hDC, hBMP, 0, BmpInfoHdr.biHeight,  
  pBitmapBuff, (LPBITMAPINFO) &BmpInfoHdr, DIB_RGB_COLORS);

   SaveAs24BMPFile("Test.bmp", pBitmapBuff, BmpInfoHdr);
   delete pBMP;
}
-------

Any comments will be appreciated.
0
Comment
Question by:okg
6 Comments
 

Author Comment

by:okg
ID: 1324968
Edited text of question
0
 

Author Comment

by:okg
ID: 1324969
Edited text of question
0
 

Author Comment

by:okg
ID: 1324970
Edited text of question
0
Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

 
LVL 12

Expert Comment

by:migel
ID: 1324971
HI! I can`t find BitBlt call in your code. According your code you don`t  capture screen? just create empty bitmap and get it`s buffer.
To capture screen you must select created bitmap into DC and copy screen buffer to them.
for example:
{
ClentToScreen(rtWnd);
HDC hDeskDC = ::GetDC(NULL);
HBITMAP hOldBm = ::SelectObject(hDC,  hBMP);
::BitBlt(hDC, hDeskDC, 0, 0, rtWnd.Width(), rtWnd.Height(), hDeskDC, rtWnd.Left, rtWnd. Top, SRCCOPY);
 ::SelectObject(hDC,  hOldBm );
::ReleaseDC(NULL, hDeskDC);
// now your hBMP contain copy of the screen image
}

0
 
LVL 6

Expert Comment

by:snoegler
ID: 1324972
I've never tried this, but maybe it works ( it works at least
with CRichEditCtrl's ...)

CWnd *pDesktopWnd=GetDesktopWindow();
CDC  *pDesktopTempDC=pDesktopWnd->GetDC();
// Create compatible DC
CDC  *pMemDC=new CDC;
CBitmap *pMemBmp=new CBitmap;
pMemDC->CreateCompatibleDC(pDesktopTempDC);
pMemBmp->CreateCompatibleBitmap(pDesktopTempDC,
                                ::GetSystemMetrics(SM_CXSCREEN),
                                ::GetSystemMetrics(SM_CYSCREEN));
// Release the temporary DC
pDesktopWnd->ReleaseDC(pDesktopTempDC);

// Select the memory bitmap
int nSDC=pMemDC->SaveDC();
pMemDC->SelectObject(pMemBmp);
// Render the desktop window into the memory bitmap
GetDesktopWindow()->SendMessage(WM_PRINT,
                                (WPARAM)pMemDC->GetSafeHdc(),
                                PRF_CLIENT|
                                PRF_ERASEBKGND|
                                PRF_CHILDREN|PRF_OWNED);
pMemDC->RestoreDC(nSDC);
delete pMemDC;

// Now pMemBmp should contain the desktops' contents.
0
 
LVL 1

Accepted Solution

by:
atari earned 100 total points
ID: 1324973
Again my code snippet, it worked, I tested it yesterday 11/18/1998:

Tried to capture screen and presented in my mdi-view:

void CMyView::OnCaptureScreen()
{
  CClientDC clientDC(this); // get my dc
  CRect windowrect;
  GetClientRect(&windowrect);
 
  HDC screenDC=::GetDC(NULL); // get desktop dc
  CDC* dc = CDC::FromHandle(screenDC);
  CRect rectDesktop;
  if (!::SystemParametersInfo(SPI_GETWORKAREA,0,&rectDesktop,0))
        ::GetWindowRect(::GetDesktopWindow(),&rectDesktop);
  else
  {
      rectDesktop.right=::GetSystemMetrics(SM_CXSCREEN);
      rectDesktop.bottom=::GetSystemMetrics(SM_CYSCREEN);
      rectDesktop.right-=rectDesktop.left;
      rectDesktop.bottom-=rectDesktop.top;
      rectDesktop.left=-rectDesktop.left;
      rectDesktop.top=-rectDesktop.top;
  }
  CBitmap bitmap;
  bitmap.CreateCompatibleBitmap(dc,rectDesktop.Width(),rectDesktop.Height());
  CDC memDC;
  CBitmap *pOldBitmap;
  memDC.CreateCompatibleDC(dc);
  pOldBitmap=memDC.SelectObject(&bitmap);
  memDC.BitBlt(0,0,rectDesktop.Width(),rectDesktop.Height(),dc,0,0,SRCCOPY);
  clientDC.StretchBlt(windowrect.left,windowrect.top,windowrect.Width(),windowrect.Height(),&memDC,0,0,rectDesktop.Width(),rectDesktop.Height(),SRCCOPY);
  memDC.SelectObject(pOldBitmap);
}

0

Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
sumNumber challenge 16 138
no14 challenge 14 70
noX challenge 17 129
Increment column based of a FK 8 31
Introduction: The undo support, implementing a stack. Continuing from the eigth article about sudoku.   We need a mechanism to keep track of the digits entered so as to implement an undo mechanism.  This should be a ‘Last In First Out’ collec…
Have you tried to learn about Unicode, UTF-8, and multibyte text encoding and all the articles are just too "academic" or too technical? This article aims to make the whole topic easy for just about anyone to understand.
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
This video shows how to quickly and easily add an email signature for all users on Exchange 2016. The resulting signature is applied on a server level by Exchange Online. The email signature template has been downloaded from: www.mail-signatures…

860 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question