Advanced MFC Programming

Chapter 10. Bitmap
}
}
if(m_pBmpMaskOld != NULL)
{
m_dcMemMask.SelectObject(m_pBmpMaskOld);
m_pBmpMaskOld=NULL;
}
if(m_pBmpBSOld != NULL)
{
m_dcMemBS.SelectObject(m_pBmpBSOld);
m_pBmpBSOld=NULL;
}
if(m_dcMem.GetSafeHdc() != NULL)m_dcMem.DeleteDC();
if(m_dcMemMask.GetSafeHdc() != NULL)m_dcMemMask.DeleteDC();
if(m_dcMemBS.GetSafeHdc() != NULL)m_dcMemBS.DeleteDC();
if(m_bmpDraw.GetSafeHandle() != NULL)m_bmpDraw.DeleteObject();
if(m_bmpMask.GetSafeHandle() != NULL)m_bmpMask.DeleteObject();
if(m_bmpBS.GetSafeHandle() != NULL)m_bmpBS.DeleteObject();
If a pointer is not NULL, it means that there is an object being currently selected by the DC, so
funciton CGDIObject::SelectObject(…) is called to select the object (palette or bitmap) out of the DC
before destroying it.
We need to call this function just before the application exits. In the sample, a WM_DESTROY message
handler is added to class CGDIView through using Class Wizard. The corresponding member function is
implemented as follows:
void CGDIView::OnDestroy()
{
CleanUp();
CScrollView::OnDestroy();
}
Loading Bitmap & Creating Mask Bitmap
In the sample, funciton CGDIView::LoadBitmap(…) is changed. In the new function, a DIB section is
created from the DIB data, and the mask bitmap image is generated from the normal image. The palette
creation precedure is still the same. The handle retruned from the DIB section is attached to variable
CGDIView::m_bmpDraw:
void CGDIView::LoadBitmap(HGLOBAL hData)
{
CPalette *pPalDraw;
CPalette *pPalOld;
CClientDC dc(this);
HBITMAP hBmp;
LPBYTE pBits;
LPBITMAPINFO lpBi;
LPLOGPALETTE lpLogPal;
int nSizeCT;
int i, j;
CGDIDoc *pDoc;
pDoc=GetDocument();
ASSERT_VALID(pDoc);
AfxGetApp()->DoWaitCursor(TRUE);
lpBi=(LPBITMAPINFO)::GlobalLock(hData);
ASSERT(lpBi);
nSizeCT=pDoc->GetColorTableSize(lpBi->bmiHeader.biBitCount);
pPalDraw=pDoc->GetPalette();
if(pPalDraw->GetSafeHandle() != NULL)pPalDraw->DeleteObject();
if(nSizeCT != 0)
{
lpLogPal=(LPLOGPALETTE) new BYTE
[
sizeof(LOGPALETTE)+(nSizeCT-1)*sizeof(PALETTEENTRY)
];
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