Re: Drawing to a Bitmap

"AliR" <AliR@online.nospam>
Thu, 19 Nov 2009 10:10:33 -0600
I have a question, do you only want the client area of the views, or do you
want to save the border and titlebar and all that?

This might be a little more than what you asked for!

Typical the way I do my view drawing is double buffered, so what I normally
do is I keep a bitmap in memory that I draw to, and then when OnDraw gets
called I simply blit the bitmap in memory to the screen.
The reason I do this is because it is much faster to simply blit a bitmap
than to loop through everything and draw every item each time a WM_PAINT is
received, because that can happen more often than my actual graphics is
going to change.
So everytime something happens that requires a change to the graphics, I
simply draw to the memory bitmap and Invalidate/UpdateWindow the view so
that the display will show the changes.

With all that said, my Drawing routine usually takes a CDC and a CRect and
draws on that DC. The cool thing here is that I can pass in any DC, screen
or memory for the draw routine to draw to.

So for me, if I want to save a bitmap of what's on the screen, all I have to
do is create a memory dc and put a bitmap in it, call my draw routine with
that DC and then simply save the bitmap to a file.

The short fall of this method is that it can be memory intensive depending
on the size of your bitmaps.


"Scoots" <> wrote in message

Hello all,

I have what I hope to be a simple question, but one that Google is
failing me on. Everything seems to describe the opposite of the
process, but I know that the information is out there somewhere.

I have an mfc application that with multiple CViews that I have draw
code set up for and everything works wonderfully when drawing to the
screen. Now, what I want to do, is create a bitmap, tell each of the
CViews to draw to that, and then saving it out to disk as a screen
capture. I want to go this route for several reasons, the biggest
being that I want to save these CViews even if they are ocluded by
other windows, though if this proves to be too difficult, a screenshot
would suffice I suppose.

My CView has draw code that looks like the following:

void CGraphicsView::OnDraw(CDC* pDCWnd)
   CGraphicsDoc* pModelDoc = GetModelDocument();

   CDC *pDC = pDCWnd;


CRect rectClient;

   CRect rectClip;

if (EqualRect(&rectClient, &rectClip))
if (m_bWasCovered)
m_bWasCovered = false;
m_bWasCovered = true;

   if (!pDC->IsPrinting())
pDC->FillSolidRect(rectClip, RGB(204, 204, 204));

   if (pModelDoc->Model()->IsValid())
        pModelDoc->Model()->Draw(pDC, rectClip);

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