C / C++ / MFC

29-Jul-09 19:38

I want to capture the desktop as an image just like printscreen function. Any Win32 API or MFC class that perform the task.

THANKS.

Adam Roderick J29-Jul-09 19:51

29-Jul-09 19:51

i think this link will surely help u Smile | :)

Various methods for capturing the screen[^]

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«_Superman_»29-Jul-09 20:20

«_Superman_»

29-Jul-09 20:20

I believe there is a better way to do the Capture it the GDI way in the article.
Instead of GetDesktopWindow() and GetDC() you can use CreateDC(_T("DISPLAY"), NULL, NULL, NULL);

«_Superman_»
I love work. It gives me something to do between weekends.

Adam Roderick J29-Jul-09 20:23

29-Jul-09 20:23

offcourse superman's suggested method is better

see the code below for help Smile | :)

HDC hDesktopDC, hMemDC;
int nXPos = 0, nYPos = 0;
int nWidth = 0, nHeight = 0;
HGDIOBJ hOldBitmap, hBitmap;

// check for an empty rectangle
if ( IsRectEmpty( lpRect_i ))
{
return NULL;
}

// create a DC for the screen and create
// a memory DC compatible to screen DC
hDesktopDC = CreateDC( _T( "DISPLAY" ), NULL, NULL, NULL );
hMemDC = CreateCompatibleDC( hDesktopDC ); // get points of rectangle to grab
nXPos = lpRect_i->left;
nYPos = lpRect_i->top;
nWidth = lpRect_i->right - lpRect_i->left;
nHeight = lpRect_i->bottom - lpRect_i->top ;

// create a bitmap compatible with the screen DC
hBitmap = CreateCompatibleBitmap( hDesktopDC, nWidth, nHeight );
// select new bitmap into memory DC
hOldBitmap = SelectObject ( hMemDC, hBitmap );
// bitblt screen DC to memory DC
BitBlt( hMemDC, 0, 0, nWidth, nHeight, hDesktopDC, nXPos, nYPos, SRCCOPY );
// select old bitmap back into memory DC and get handle to
// bitmap of the screen
hBitmap = SelectObject( hMemDC, hOldBitmap );
// clean up
DeleteDC( hDesktopDC );
DeleteDC( hMemDC );
// return handle to the bitmap
return ( HBITMAP )hBitmap;

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Madhu_Rani29-Jul-09 21:43

29-Jul-09 21:43

Thanks all of you for guidance and providing me a couple of alternates to perform the task. I would implement the stuff then I would be back , if i face some problem.....

Madhu_Rani29-Jul-09 23:17

29-Jul-09 23:17

Sorry, I have to ask very primitive questions but I did some work in VC++ around 9 years back and now forget every thing. Even I have to struggle to play with AfxMessageBox these days Smile | :)

Anyhow, now I want to display the captured image. The image is captured in HBITMAP hCaptureBitmap, so what class I should use to display the image. Suppose I have SDI based application and in View class what should I do......

Adam Roderick J29-Jul-09 23:35

29-Jul-09 23:35

no more direct code

Clue :-

1. device context.
2. SelectObject
3. bitBlt

Now try yourself Smile | :)

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Madhu_Rani29-Jul-09 23:41

29-Jul-09 23:41

You mean , I should get the DC in view class by calling some thing like GetDC , then Select that DC and at the end by using bitBlt should display in the view class....

hmmm. what about if I take an object of Picturebox and then assign the handler of Bitmap to it. but I guess u are right there is no need to take an object of PictureBox, rather view class can be work as a placeholder as well. let me try

Adam Roderick J30-Jul-09 0:00

30-Jul-09 0:00

yes u should try Thumbs Up | :thumbsup:

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Madhu_Rani30-Jul-09 0:05

Re: Win32API/MFC to capture desktop as an image [modified]

30-Jul-09 0:05

void CSDITESTView::OnFileTest()
{
int nScreenWidth = GetSystemMetrics(SM_CXSCREEN);
int nScreenHeight = GetSystemMetrics(SM_CYSCREEN);

HWND hDesktopWnd = GetDesktopWindow()->m_hWnd;

HDC hDesktopDC = ::GetDC(hDesktopWnd);
HDC hCaptureDC = CreateCompatibleDC(hDesktopDC);
HBITMAP hCaptureBitmap =CreateCompatibleBitmap(hDesktopDC,nScreenWidth, nScreenHeight);
SelectObject(hCaptureDC,hCaptureBitmap);
BitBlt(hCaptureDC,0,0,nScreenWidth,nScreenHeight, hDesktopDC,0,0,SRCCOPY|CAPTUREBLT);
::ReleaseDC(hDesktopWnd,hDesktopDC);
DeleteDC(hCaptureDC);

}

I guess this code should work as it is doing the all stuff already, but it not displaying anything ? why

Adam Roderick J30-Jul-09 0:31

30-Jul-09 0:31

Who will call the paint?

clue
1. Some one should call painting, isnt Smile | :)

Just simple, usually it is not done to give the whole code,
well check the below code.

HBITMAP CopyScreen( LPRECT lpRect_i )
{
HDC hDesktopDC, hMemDC;
int nXPos = 0, nYPos = 0;
int nWidth = 0, nHeight = 0;
HGDIOBJ hOldBitmap, hBitmap;

// check for an empty rectangle
if ( IsRectEmpty( lpRect_i ))
{
return NULL;
}

// create a DC for the screen and create
// a memory DC compatible to screen DC
hDesktopDC = CreateDC( _T( "DISPLAY" ), NULL, NULL, NULL );
hMemDC = CreateCompatibleDC( hDesktopDC ); // get points of rectangle to grab
nXPos = lpRect_i->left;
nYPos = lpRect_i->top;
nWidth = lpRect_i->right - lpRect_i->left;
nHeight = lpRect_i->bottom - lpRect_i->top ;

// create a bitmap compatible with the screen DC
hBitmap = CreateCompatibleBitmap( hDesktopDC, nWidth, nHeight );
// select new bitmap into memory DC
hOldBitmap = SelectObject ( hMemDC, hBitmap );
// bitblt screen DC to memory DC
BitBlt( hMemDC, 0, 0, nWidth, nHeight, hDesktopDC, nXPos, nYPos, SRCCOPY );
// select old bitmap back into memory DC and get handle to
// bitmap of the screen
hBitmap = SelectObject( hMemDC, hOldBitmap );
// clean up
DeleteDC( hDesktopDC );
DeleteDC( hMemDC );
// return handle to the bitmap
return ( HBITMAP )hBitmap;
}

void CSlideshawDlg::OnFirst()
{
RECT rect;
rect.left = 150;
rect.bottom = 500;
rect.top = 150;
rect.right = 500;
HBITMAP hBit = CopyScreen( &rect );
CDC memdc1;
CClientDC dc(this);
memdc1.CreateCompatibleDC(&dc);
memdc1.SelectObject( hBit );
dc.BitBlt(150,150,500,500,&memdc1,0,0,SRCCOPY);
}

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modified on Thursday, July 30, 2009 7:01 AM

Madhu_Rani30-Jul-09 1:59

30-Jul-09 1:59

This is what I cooked, but it is not working... I know there is Invalidate() but it call onpaint again, so why we call it here.

void CSDITESTView::OnFileTest()
{

//m_pDC store the CDC pointer in OnDraw() function.

CDeskTop desktop;
CBitmap bitmap;
HWND hWnd=NULL;
bitmap.Attach(desktop.GetDeskTopImage());
BITMAP bm;
bitmap.GetBitmap(&bm );

CDC memDC;
CClientDC dc(this);
memDC.CreateCompatibleDC(&dc);
memDC.SelectObject(&bitmap );
m_pDC->BitBlt(0, 0, bm.bmWidth, bm.bmHeight, &memDC, 0, 0,SRCCOPY);
}

HBITMAP CDeskTop:: GetDeskTopImage()
{
int nScreenWidth = GetSystemMetrics(SM_CXSCREEN);
int nScreenHeight = GetSystemMetrics(SM_CYSCREEN);
HWND hDesktopWnd = GetDesktopWindow();
HDC hDesktopDC = GetDC(hDesktopWnd);
HDC hCaptureDC = CreateCompatibleDC(hDesktopDC);
HBITMAP hCaptureBitmap =CreateCompatibleBitmap(hDesktopDC,nScreenWidth, nScreenHeight);
SelectObject(hCaptureDC,hCaptureBitmap);
BitBlt(hCaptureDC,0,0,nScreenWidth,nScreenHeight, hDesktopDC,0,0,SRCCOPY|CAPTUREBLT);
ReleaseDC(hDesktopWnd,hDesktopDC);
DeleteDC(hCaptureDC);
return hCaptureBitmap;

}

Madhu_Rani30-Jul-09 2:05

30-Jul-09 2:05

Now I got the solution.

m_pDC->BitBlt(0, 0, bm.bmWidth, bm.bmHeight, &memDC, 0, 0,SRCCOPY);

dc.BitBlt(0, 0, bm.bmWidth, bm.bmHeight, &memDC, 0, 0,SRCCOPY);

I replaced m_pDC with dc. and now it works.

THANKS A LOT INDEED FOR YOUR CONTINOUS HELP