Win32API/MFC to capture desktop as an image

[Adam Roderick J]

offcourse superman's suggested method is better see the code below for help :) 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_Rani]

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_Rani]

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:) 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 J]

no more direct code Clue :- 1. device context. 2. SelectObject 3. bitBlt Now try yourself :)

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[Madhu_Rani]

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 J]

yes u should try :thumbsup:

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[Madhu_Rani]

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 J]

Who will call the paint? clue 1. Some one should call painting, isnt :) 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_Rani]

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_Rani]

:) 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

[Asharudeed]

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.