Advanced MFC Programming

Chapter 10. Bitmap
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}
DECLARE_DYNCREATE(CGDIView)
Altogether there are four CBitmap type variables, three CBitmap type pointers, three CDC type variables,
and three CPalette type pointers. Their meanings are explained in the following table:
Variable
m_bmpDraw
m_bmpMask
m_bmpBS
m_dcMem
m_dcMemMask
m_dcMemBS
m_pBmpOld
m_pBmpMaskOld
m_pBmpBSOld
m_pPalOld
m_pPalMaskOld
m_pPalBSOld
Meaning
Load the normal bitmap image.
Store the mask bitmap image.
Used for creating memory bitmap.
Selects m_bmpDraw.
Selects m_bmpMask.
Selects m_bmpBS.
Used for selecting m_bmpDraw out of m_dcMem.
Used for selecting m_bmpMask out of m_dcMemMask.
Used for selecting m_bmpBS out of m_dcMemBS.
Used for selecting the logical palette out of m_dcMem.
Used for selecting the logical palette out of m_dcMemMask.
Used for selecting the logical palette out of m_dcMemBS.
To make the application more interesting, we will also draw the background of client window using
bitmap. This bitmap will be loaded into m_bmpBkd variable.
The six pointers are initialized to NULL in the constructor:
CGDIView::CGDIView()
{
m_bBitmapLoaded=FALSE;
m_pBmpOld=NULL;
m_pBmpMaskOld=NULL;
m_pBmpBSOld=NULL;
m_pPalOld=NULL;
m_pPalMaskOld=NULL;
m_pPalBSOld=NULL;
}
Cleaning Up
A new function CGDIView::CleanUp() is added to the application for doing the clean up job. Within
this function, all the objects selected by the DCs are selected out, then DCs and bitmaps are deleted:
void CGDIView::CleanUp()
{
if(m_pPalOld != NULL)
{
m_dcMem.SelectPalette(m_pPalOld, FALSE);
m_pPalOld=NULL;
}
if(m_pPalMaskOld != NULL)
{
m_dcMemMask.SelectPalette(m_pPalMaskOld, FALSE);
m_pPalMaskOld=NULL;
}
if(m_pPalBSOld != NULL)
{
m_dcMemBS.SelectPalette(m_pPalBSOld, FALSE);
m_pPalBSOld=NULL;
}
if(m_pBmpOld != NULL)
{
m_dcMem.SelectObject(m_pBmpOld);
m_pBmpOld=NULL;
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