Re: Win32API/MFC to capture desktop as an image - C / C++ / MFC Discussion Boards

Re: Win32API/MFC to capture desktop as an image

«_Superman_»29-Jul-09 20:20

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.

Re: Win32API/MFC to capture desktop as an image

Adam Roderick J29-Jul-09 20:23

Adam Roderick J

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;

Величие не Бога может быть недооценена.

Re: Win32API/MFC to capture desktop as an image

Madhu_Rani29-Jul-09 21:43

Madhu_Rani

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.....

Re: Win32API/MFC to capture desktop as an image

Madhu_Rani29-Jul-09 23:17

Madhu_Rani

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......

Re: Win32API/MFC to capture desktop as an image

Adam Roderick J29-Jul-09 23:35

Adam Roderick J

29-Jul-09 23:35

no more direct code

Clue :-

1. device context.
2. SelectObject
3. bitBlt

Now try yourself Smile | :)

Величие не Бога может быть недооценена.

Re: Win32API/MFC to capture desktop as an image

Madhu_Rani29-Jul-09 23:41

Madhu_Rani

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

Re: Win32API/MFC to capture desktop as an image

Adam Roderick J30-Jul-09 0:00

Adam Roderick J

30-Jul-09 0:00

yes u should try Thumbs Up | :thumbsup:

Величие не Бога может быть недооценена.

Re: Win32API/MFC to capture desktop as an image

Madhu_Rani30-Jul-09 0:05

Madhu_Rani

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

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

Adam Roderick J30-Jul-09 0:31

Adam Roderick J

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);
}

Величие не Бога может быть недооценена.

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

Re: Win32API/MFC to capture desktop as an image

Madhu_Rani30-Jul-09 1:59

Madhu_Rani

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;

}

Re: Win32API/MFC to capture desktop as an image

Madhu_Rani30-Jul-09 2:05

Madhu_Rani

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

Re: Win32API/MFC to capture desktop as an image

Asharudeed16-Feb-10 4:23

Asharudeed

16-Feb-10 4:23

Hi..

Basically I am working with CPP console application. Could any one update me, to capture screenshot of Desktop (by using the code mentioned in this thread).. whether I need to use MFC project or ATL based Project.

Any guidelines will help me a lot.

Thanks in advance.

emBDA.sys BSOD!!! [modified]

Kiran Satish29-Jul-09 19:00

Kiran Satish

29-Jul-09 19:00

Hi all,

I just got a new simple USB framegrabber which uses emBDA.sys (pretty common driver used by many USB frame grabbers/TV tuners these days) and when I try to access it in my MFC program, it BSODs right away with emBDA.sys error (8E code). But when I use their application to capture with the framegrabber, it works fine. I tried it on couple of systems with same result.
It happens as soon as I call capDlgVideoSource(GetSafeHwnd()); command.
Does anyone came accross this problem with accessing this driver before??

Any suggestions for using alternate drivers??

thanks,

PKNT

CRect

kumar sanghvi29-Jul-09 18:45

kumar sanghvi

29-Jul-09 18:45

Hi,
how can i get the fixed border or proportional border for a rect...

how to convert the matlab left matrix division \ into cv++ with opencv?

DevelopmentNoob29-Jul-09 16:23

DevelopmentNoob

29-Jul-09 16:23

i'm now wanna to convert the matlab left matrix division \ into cv++ with opencv.
i have no ideal about it. the matlab help file also not help me a lot to understand the algorithm.anyone can help me or gv me the suggestion? I'm waiting your reply.Thank you！

"Assertion Failed" with thread and device context

nautilusvn29-Jul-09 16:11

nautilusvn

29-Jul-09 16:11

Hi all,

I write a MFC program that will execute a drawing circle in another thread when I click on somewhere in client area and I got it.

My problem is when I click various time (and quickly) it sometime gives me an "Assertion Failed" error.

here is my code:

void CGSimView::OnLButtonDown(UINT nFlags, CPoint point) 
{
        ...
	DCPOINT info;
	PTPOINT3D currentPoint = pDoc->m_graph.GetNode(point.x,point.y);
	
	if(currentPoint != NULL)
	{
		this->m_nodeIndex = currentPoint->index;

		info.hwnd = this->GetSafeHwnd();
		this->GetClientRect(&info.rect);
		info.point = currentPoint;

		AfxBeginThread(onGetFocus,&info);
	}
	
	
	CView::OnLButtonDown(nFlags, point);
}

UINT onGetFocus(LPVOID param)
{

	DCPOINT *info = (DCPOINT*)param;

	HDC hdc = GetDC(info->hwnd);
		
	PTPOINT3D p = info->point;
	int i, temp;
	CRect rect = info->rect;
	HPEN hPen, hOldPen;

	hPen = CreatePen(PS_SOLID,1,RGB(225,0,0));

	hOldPen = (HPEN)SelectObject(hdc, hPen);

	for(i=0;i<9;i++)
	{
		temp = 10+i;
		Ellipse(hdc,p->x - temp,p->y - temp,p->x + temp, p->y + temp);
		Sleep(10);
	}

	SelectObject(hdc, hOldPen);
	DeleteObject(hPen);

	return 0;
}

please help me to solve this.
Thank in advance.

Re: "Assertion Failed" with thread and device context

Richard Andrew x6429-Jul-09 16:51

Richard Andrew x64

29-Jul-09 16:51

When it gives "Assert failed", click "Retry" to debug the program.

The code around the Assert statement usually gives a clue as to why it is failing. Sometimes there's a comment that tells explicitly why it might fail.

Re: "Assertion Failed" with thread and device context

nautilusvn29-Jul-09 17:25

nautilusvn

29-Jul-09 17:25

Thank Richard,

I have followed as your advise and the Debugger points to this line of my code:

Ellipse(hdc, p->x - temp, p->y - temp, p->x + temp, p->y + temp);

It says "Access violation".

I guess that it has some conflict between threads on the device context I've used. But I don't know how to solve it.
Please help!

Re: "Assertion Failed" with thread and device context

Richard Andrew x6429-Jul-09 17:31

Richard Andrew x64

29-Jul-09 17:31

When you debug it, inspect the variable "p" to be sure that it points to a valid object.

That may be the source of the access violation.

Re: "Assertion Failed" with thread and device context

Richard Andrew x6429-Jul-09 17:35

Richard Andrew x64

29-Jul-09 17:35

I failed to notice something serious:

You're trying to draw in the window with a secondary thread.

This is not allowed in MFC.

You must do all your drawing with the same thread that owns the window.

Re: "Assertion Failed" with thread and device context

nautilusvn29-Jul-09 20:27

nautilusvn

29-Jul-09 20:27

Thank Richard,

I greatly appreciate your help to me.

But now I'm completely surprised that drawing in the window with a secondary thread is not allowed in MFC.

Actually I'm writing a simple game, when my user selects an object on screen, I want my user take focus on that object by a moving circle around it. How people do that with MFC?

Thank

Re: "Assertion Failed" with thread and device context

Richard Andrew x6430-Jul-09 4:14

Richard Andrew x64

30-Jul-09 4:14

One way of doing it is to send a message to your window, and then handle the message in your WndProc function by drawing in the window.

See this article in MSDN. It describes the problem I mentioned:

http://msdn.microsoft.com/en-us/library/h14y172e(VS.80).aspx[^]

Re: "Assertion Failed" with thread and device context

krmed30-Jul-09 6:53

krmed

30-Jul-09 6:53

One thing I see that could also be part of your problem is that you do a GetDC() in your thread, and then you properly select the new pen, use it, select the old pen and delete it, but I don't see anywhere that you do a ReleaseDC().

This probably isn't the entire problem, but you should always release the DC after you use it that way.

Hope that helps.

Karl - WK5M
PP-ASEL-IA (N43CS)
PGP Key: 0xDB02E193
PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193

Passing multi-dimensional array from C# to Win32 C++ dll? [modified] [MOVED TO C++/CLI]

devvvy29-Jul-09 16:03

devvvy

29-Jul-09 16:03

[moved to C++/CLI forum]

dev

modified on Wednesday, July 29, 2009 10:51 PM

Re: Passing multi-dimensional array from C# to Win32 C++ dll?

Richard Andrew x6429-Jul-09 16:48

Richard Andrew x64

29-Jul-09 16:48

You might have better luck posting this question in the C++/CLI forum.

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.