Advanced MFC Programming

Chapter 10. Bitmap
SRCCOPY
);
m_dcMemBS.BitBlt
(
0,
0,
bm.bmWidth,
bm.bmHeight,
&m_dcMem,
0,
0,
SRCINVERT
);
m_dcMemBS.BitBlt
(
0,
0,
bm.bmWidth,
bm.bmHeight,
&m_dcMemMask,
0,
0,
SRCAND
);
m_dcMemBS.BitBlt
(
0,
0,
bm.bmWidth,
bm.bmHeight,
&m_dcMem,
0,
0,
SRCINVERT
);
pDC->BitBlt
(
0,
0,
bm.bmWidth,
bm.bmHeight,
&m_dcMemBS,
0,
0,
SRCCOPY
);
}
pDC->SelectPalette(pPalOld, FALSE);
In the above function, the pattern on the target device is first copied to the memory bitmap. Then
function CDC::BitBlt(…) is called three times to draw the normal image and mask image on the memory
bitmap, with two XOR drawings of the normal image (first and thrid operations) and one AND mode
drawing of the mask image (second operation). Finally, the new pattern in the memory bitmap is copied
back to the targert device.
Adding Background
If the window’s background is also white, it is difficult for us to see the transparency effect. To show
this effect, in the sample, the background of the client window is also painted with a bitmap image.
The image that is used to paint the background is prepared as a resource, whose ID is IDB_BITMAPBKD.
The bitmap is loaded to variable CGDIView::m_bmpBkd in function CGDIView:: OnInitialUpdate():
void CGDIView::OnInitialUpdate()
{
CGDIDoc *pDoc;
HGLOBAL hData;
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