Advanced MFC Programming

Chapter 10. Bitmap
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}
HGLOBAL ConvertDDBtoDIB(CBitmap *);
DWORD GetColorTableSize(WORD);
Function CGDIDoc::ConvertDDBtoDIB(…) converts DDB to DIB, its input parameter is a CBitmap type
pointer and its return value is a global memory handle. Function CGDIDoc::GetColorTableSize(…) is used
to calculate the size of color table from bit count per pixel information (In the previouse samples, color
table size calculation is implemented within function CGDIView::OnInitialUpdate(). Since we need color
table size information more frequently now, this calculation is implemented as a single member function):
DWORD CGDIDoc::GetColorTableSize(WORD wBitCount)
{
DWORD dwSizeCT;
}
switch(wBitCount)
{
case 1:
{
dwSizeCT=2;
break;
}
case 4:
{
dwSizeCT=16;
break;
}
case 8:
{
dwSizeCT=256;
break;
}
case 24:
{
dwSizeCT=0;
}
}
return dwSizeCT;
In function CGDIDoc::ConvertDDBtoDIB(…), first we must obtain a handle to the client window that
can be used to create a DC:
HGLOBAL CGDIDoc::ConvertDDBtoDIB(CBitmap *pBmp)
{
BITMAP bm;
BITMAPINFOHEADER bi;
LPBITMAPINFO lpBi;
DWORD dwSizeCT;
DWORD dwDibLen;
CGDIView *ptrView;
POSITION pos;
CPalette *pPalOld;
HGLOBAL hDib;
……
}
pos=GetFirstViewPosition();
ptrView=(CGDIView *)GetNextView(pos);
ASSERT(ptrView->IsKindOf(RUNTIME_CLASS(CGDIView)));
CClientDC dc(ptrView);
Then function CBitmap::GetBitmap(…) is called to retrieve the information of bitmap and allocate
enough buffers for storing structure BITMAPINFOHEADER and color table:
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