Advanced MFC Programming

Chapter 11. Sample: Simple Paint
color table size to starting addresses of the DIB buffer. Since one raster line must use multiple of 4 bytes,
we need to use WIDTHBYTES macro to calculate the actual bytes that are used by one raster line. The
following shows how the selected rectangular area of the bitmap is copied to the target bitmap:
……
……
for(i=0; ibmiHeader.biBitCount*lpBi->bmiHeader.biWidth
)*(lpBi->bmiHeader.biHeight-sizeTgtOffset.cy-i-1)
);
memcpy
(
lpRowTgt,
lpRowSrc,
WIDTHBYTES(lpBi->bmiHeader.biBitCount*rectSrc.Width())
);
}
Cut & Copy
With function CGDIDoc::CreateCopyCutDIB(…), it is much easier to implement cut and copy
commands. For copy command, we need to open the clipboard, empty it, set clipboard data, and close the
clipboard. For the cut command, we also need to fill the selected area with the current background color.
The following shows how the cut command is implemented:
void CGDIDoc::OnEditCut()
{
if(GetCGDIView()->OpenClipboard() == TRUE)
{
HGLOBAL hDIB;
}
}
::EmptyClipboard();
hDIB=CreateCopyCutDIB();
ASSERT(hDIB != NULL);
::SetClipboardData(CF_DIB, hDIB);
::CloseClipboard();
GetCGDIView()->FillSelectionWithBgdColor();
UpdateAllViews(NULL);
Paste
Paste command is the reverse of cut or copy command: we need to obtain DIB data from the clipboard
and copy it back to the bitmap image that is being edited. To let the user place pasted image everywhere,
we need to implement tracker again to select the pasted image. With this implementation, the user can
move or resize the image surrounded by the tracker just like using the rectangular selection tool.
So instead of copying DIB data from the clipboard directly to the bitmap being edited, we can first
create and copy it to the backup bitmap image (CGDIView::m_bmpSelBackup), then change the current
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