How to get an file-loaded bitmap to fit a static image container using StretchBlt ?

[Mike Pliam]

Sounds easy. But it's not. Here's my attempt. It crashes the app apparently due to heap corruption related to byte counts. Inspection of my code will reveal that I am confused about how to create compatible device contexts (DC), what dimensions to use, how to get the dimensions of the newly loaded bitmap, how to create a thumbnail bitmap (rather than just the handle ?), how to 'deselect' an object, how to 'destroy' a DC, and just about everything else.

	// Load the Image File
	HBITMAP hBmp = (HBITMAP)::LoadImage(NULL, m_csPathname, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE|LR_CREATEDIBSECTION);

	// create a compatible memory context
	HDC memDCdst; 
	CDC * pDC = m_cImage.GetDC();
	memDCdst = CreateCompatibleDC(pDC->m_hDC);

	// create compatible thumbnail bitmap of the size of your static control 
	CRect rect;
	m_cImage.GetWindowRect(rect);
	ScreenToClient(rect);
	int bmpWidth = rect.Width();
	int bmpHeight = rect.Height();
	HBITMAP hBmpDst = CreateCompatibleBitmap(memDCdst, bmpWidth, bmpHeight);

	// select the thumbnail bitmap into Dst 
	SelectObject(memDCdst, hBmpDst);

	// create compatible memory context Src 
	HDC memDCsrc;
	memDCsrc = CreateCompatibleDC(memDCdst);   // use the destination DC (or what ??)

	// select your previously loaded image bitmap into Src 
	SelectObject(memDCsrc, hBmp);

	// pre-calculate Dst target rectangle (optional, 2) - done above
	int xDest = rect.TopLeft().x;
	int yDest = rect.TopLeft().y;
	int wDest = rect.Width();
	int hDest = rect.Height();
	
	// do StrechBlt to Dst from Src 
	StretchBlt(memDCdst, xDest, yDest, wDest, hDest, memDCsrc, 0, 0, bmpWidth, bmpHeight, SRCCOPY);

	// unselect the loaded bitmap from Src 
	// The SelectObject function selects an object into the specified device context (DC). 
	// The new object replaces the previous object of the same type.
	SelectObject(memDCsrc, hBmpDst);

	// unselect the thumbnail bitmap from Dst 
	SelectObject(memDCdst, hBmpDst);

	// destroy Dst context 
	delete memDCdst;
	memDCdst = NULL;

	// destroy Src context 
	delete memDCsrc;
	memDCsrc = NULL;

	// set thumbnail bitmap to static control 
	m_cImage.SetBitmap(hBmpDst);