C / C++ / MFC

void CMyGridCtrl::InitImageList()
{
	// this code works fine (the default image being displayed is the all-white bitmap)
	if (m_ResultsImages.Create(34, 21, ILC_COLOR4, 0, 1))
	{
		CBitmap bmp;
		CBitmap* pBmpMask = NULL;
		// bitmap loaded below is an all-white bitmap
		bmp.LoadBitmap(IDB_RESULTS_BOTH_CLEAR);
		m_ResultsImages.Add(&bmp, pBmpMask);
		SetImageList(&m_ResultsImages);
	}
}

//------------------------------------------------------------------------------
// Takes the current imagelist and applies new bitmaps according to consult/labs 
// results status.
//------------------------------------------------------------------------------
void CMyGridCtrl::BuildImageList(int nConsultID, int nLabsID)
{
	// this code words fine (I get the bitmap ID's that I expect)
	UINT nImgConsult = 0;
	UINT nImgLabs    = 0;
	switch(nConsultID) // consult
	{
		case 1  : // ordered
			nImgConsult = IDB_CONSULT_ORDERED;
			break;
		case 3  : // ordered
			nImgConsult = IDB_CONSULT_RETURNED;
			break;
		default : // cleared
			nImgConsult = IDB_NORESULTS;
			break;
	}
	switch(nLabsID) // consult
	{
		case 2  : // ordered
			nImgLabs = IDB_LABS_ORDERED;
			break;
		case 4  : // ordered
			nImgLabs = IDB_LABS_RETURNED;
			break;
		default : // cleared
			nImgLabs = IDB_NORESULTS;
			break;
	}

	// LOOK HERE
	// this is the part that doesn't seem to work.
	int      nTargetWidth  = 34;
	int      nTargetHeight = 21;
	int      nSrcWidth     = 17;
	int      nSrcHeight    = 21;
	CBitmap  bmpConsult;
	CBitmap  bmpLabs;
	CBitmap  bmpTarget;

	bmpConsult.LoadBitmap(nImgConsult);
	bmpLabs.LoadBitmap(nImgLabs);
	bmpTarget.LoadBitmap(IDB_RESULTS_BOTH_CLEAR);

	COLORREF crBackground  = RGB(0,0,0);
	CBitmap* pOldTargetBmp = NULL;
	CBitmap* pOldSourceBmp = NULL;
	CBitmap* pNewTargetBmp = NULL;
	CDC      targetDC;
	CDC      sourceDC;

	targetDC.CreateCompatibleDC(this->GetDC());
	sourceDC.CreateCompatibleDC(this->GetDC());

	pOldTargetBmp = targetDC.SelectObject(&bmpTarget);
	pOldSourceBmp = sourceDC.SelectObject(&bmpConsult);

	targetDC.BitBlt(0, 0, nTargetWidth, nTargetHeight, &sourceDC, 0, 0, SRCPAINT);
	pOldSourceBmp = sourceDC.SelectObject(&bmpLabs);
	targetDC.BitBlt(nSrcWidth, 0, nTargetWidth, nTargetHeight, &sourceDC, 0, 0, SRCPAINT);
	pNewTargetBmp = targetDC.SelectObject(pOldTargetBmp);
	m_ResultsImages.Replace(0, pNewTargetBmp, NULL);

}

targetDC.BitBlt(nSrcWidth, 0, nTargetWidth, nTargetHeight, &sourceDC, 0, 0, SRCPAINT);
pNewTargetBmp = targetDC.SelectObject(pOldTargetBmp);

// new code here
CBitmap newBmp;
BYTE bmpBits[4096];
memset(&bmpBits, 0, sizeof(bmpBits));
DWORD nSize = pNewTargetBmp->GetBitmapBits(sizeof(bmpBits), &bmpBits);
newBmp.CreateBitmap(nTargetWidth, nTargetHeight, 1, nSize, (void*)bmpBits);
// new code stops

m_ResultsImages.Replace(0, pNewTargetBmp, NULL);