• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 506
  • Last Modified:

How to Capture Screen ?

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
okg
Asked:
okg
1 Solution
 
okgAuthor Commented:
Edited text of question
0
 
okgAuthor Commented:
Edited text of question
0
 
okgAuthor Commented:
Edited text of question
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
migelCommented:
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
 
snoeglerCommented:
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
 
atariCommented:
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

Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now