Getting pixel Data from a Bitmap Handle

[robione]

The article I was reading is at (http://www.codeguru.com/forum/showthread.php?t=412541)

Here's the working code:

int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
	HWND hWnd;
	HDC hDesktopDC = ::GetDC(::GetDesktopWindow());
	HDC hMemDC = ::CreateCompatibleDC(hDesktopDC);
	int iHRes = ::GetDeviceCaps(hDesktopDC,DESKTOPHORZRES),
		iVRes = ::GetDeviceCaps(hDesktopDC,DESKTOPVERTRES),
		iBPP = ::GetDeviceCaps(hDesktopDC,BITSPIXEL),
		iClrPlane = ::GetDeviceCaps(hDesktopDC,PLANES);
	unsigned int iAlloc = iHRes*iVRes*(iBPP >> 3)*iClrPlane;

	BYTE *bySrcData,
		 *byDestData = new unsigned char[iAlloc];

	HBITMAP hBMP;
	HDC hDC; 
	HGLRC hRC;
	MSG msg;
	BITMAPINFO bi;
	RECT r;

	::memset(&bi.bmiHeader,0,sizeof(bi.bmiHeader));

	bi.bmiHeader.biSize = sizeof(bi.bmiHeader);
	bi.bmiHeader.biWidth = iHRes;
	bi.bmiHeader.biHeight = iVRes;
	bi.bmiHeader.biPlanes = iClrPlane;
	bi.bmiHeader.biBitCount = iBPP;

	::Initialize(hInstance,hWnd,nCmdShow);
	::InitOGL(hWnd,hDC,hRC,r);

	::glPixelZoom((float)r.right/(float)iHRes,(float)r.bottom/(float)iVRes);

	hBMP = ::CreateDIBSection(hMemDC,&bi,DIB_RGB_COLORS,(void **)&bySrcData,NULL,0);
	::SelectObject(hMemDC,hBMP);

	do {
		if(::PeekMessage(&msg,NULL,0,0,PM_REMOVE)) {
			::TranslateMessage(&msg);
			::DispatchMessage(&msg);
		}
		::BitBlt(hMemDC,0,0,iHRes,iVRes ,hDesktopDC,0,0,SRCCOPY);

		::memcpy(byDestData,bySrcData,iAlloc);
		
//		::Laplace(bySrcData,byDestData,iHRes,iVRes);
		::glDrawPixels(iHRes,iVRes, GL_RGBA/*GL_LUMINANCE*/, GL_UNSIGNED_BYTE, byDestData);
		::glFlush();
		::SwapBuffers(hDC);
	} while( msg.message != WM_QUIT);

	::wglMakeCurrent(NULL,NULL);
	::ReleaseDC(hWnd,hDC);
	::wglDeleteContext(hRC);

	::SelectObject(hMemDC,NULL);
	::ReleaseDC(NULL,hMemDC);
	::DeleteObject(hBMP);

	delete[] byDestData;

	return 0;
}