Advanced MFC Programming

Chapter 11. Sample: Simple Paint
……
);
::SetDIBits
(
dc.GetSafeHdc(),
(HBITMAP)m_bmpSelBackup.GetSafeHandle(),
0,
lpBi->bmiHeader.biHeight,
(LPVOID)
(
(LPSTR)lpBi+
sizeof(BITMAPINFOHEADER)+
pDoc->GetColorTableSize
(
lpBi->bmiHeader.biBitCount
)*sizeof(RGBQUAD)
),
lpBi,
DIB_RGB_COLORS
);
When calling function ::SetDIBits(…), we need to provide the handle of client window (to its first
parameter). This is because the image will finally be put to the client window. Also we need to provide the
handle of target bitmap image (to the second parameter). The third and fourth parameters of this function
specify the first raster line and total number of raster lines in the target bitmap respectively. The fifth
parameter is a pointer to the source DIB bit values (stored as an array of bytes). The sixth parameter is a
pointer to bitmap header, and final parameter specifis how to use the palette. Since we want the DIB bits to
indicate the color table contained in the DIB data, we should choose DIB_RGB_COLORS flag.
After copying the image, we need to enable the tracker, backup the current bitmap, copy the new
bitmap to the area specified by tracker rectangle, and set the current drawing tool to rectangular selection.
Then, we need to update the client window. The following portion of function CGDIView::PasteDIB(…)
shows how these are implemented:
……
……
m_trackerSel.m_rect=CRect
(
0,
0,
nRatio*lpBi->bmiHeader.biWidth,
nRatio*lpBi->bmiHeader.biHeight
);
BackupCurrentBmp();
StretchCopySelection();
Invalidate();
::GlobalUnlock(hData);
((CMainFrame *)(AfxGetApp()->m_pMainWnd))->SendMessage
(
WM_COMMAND, ID_BUTTON_RECTSEL, 0
);
Because the rectangular selection button is not actually pressed by the user, we need to generate a
WM_COMMAND message in the program and send it to the mainframe window. When doing this, WPARAM
parameter of the message is set to the ID of rectangle selection command. This will have the same effect
with clicking the rectangular selection button using the mouse.
With the above implementation, we can execute cut, copy and paste commands now. Please note that
these commands work correctly only if the currently loaded image is 256-color format. For the other
formats, error message may be generated.
11.10 Palette Change & Flickering
Sample 11.10\GDI is based on sample 11.9\GDI.
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