Advanced MFC Programming

Chapter 10. Bitmap
}
pPalDraw=pDoc->GetPalette();
pPalDraw->CreatePalette(lpLogPal);
delete [](BYTE *)lpLogPal;
……
pPalOld=dc.SelectPalette(pPalDraw, FALSE);
dc.RealizePalette();
The color table is obtained from member bmiColors of structure BITMAPINFO (pointed by lpBi). Since
the palette is stored in the document, we first call CGDIDoc::GetPalette() to obtain the address of the
palette (CGDIDoc::m_palDraw), then call CPalette::CreatePalette(…) to create the palette. After this we
select the palette into the client DC, and call CDC::RealizePalette() to let the logical palette be mapped
to the system palette.
Then, we create the DDB from DIB data:
……
……
hBmp=::CreateDIBitmap
(
dc.GetSafeHdc(),
&lpBi->bmiHeader,
CBM_INIT,
(LPSTR)lpBi+sizeof(BITMAPINFOHEADER)+sizeof(RGBQUAD)*nSizeCT,
lpBi,
DIB_RGB_COLORS
);
ASSERT(hBmp);
dc.SelectPalette(pPalOld, FALSE);
pBmp=pDoc->GetBitmap();
pBmp->Attach(hBmp);
Function ::CreateDIBitmap(…) returns an HBITMAP type handle, which must be associated with a
CBitmap type varible by calling function CBitmap::Attach(…).
The rest part of this funciton fills variable CGDIView::m_bmInfo with bitmap information, sets the
scroll sizes, create the memory DC, select bitmap and palette into it, then free the bitmap resource loaded
before:
……
}
}
pBmp->GetBitmap(&m_bmInfo);
SetScrollSizes(MM_TEXT, CSize(m_bmInfo.bmWidth, m_bmInfo.bmHeight));
m_dcMem.CreateCompatibleDC(&dc);
m_pBmpMemOld=m_dcMem.SelectObject(pBmp);
m_pPalMemOld=m_dcMem.SelectPalette(pPalDraw, FALSE);
::FreeResource(hData);
Because the bitmap and the palette are selected into the memory DC here, we must select them out
before application exits. The best place to do this is in WM_DESTROY message handler. In the sample, a
WM_DESTROY message handler is added to class CGDIView through using Class Wizard, and the
corresponding function CGDIView::OnDestroy() is implemented as follows:
void CGDIView::OnDestroy()
{
m_dcMem.SelectPalette(m_pPalMemOld, FALSE);
m_dcMem.SelectObject(m_pBmpMemOld);
}
CScrollView::OnDestroy();
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