Drawing to a Bitmap
in [MFC]
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From: Scoots on 18 Nov 2009 18:07 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(); ASSERT_VALID(pModelDoc); CDC *pDC = pDCWnd; OnPrepareDC(pDC); theApp.m_mtxDrawInProgress.Lock(); CRect rectClient; GetClientRect(&rectClient); CRect rectClip; pDCWnd->GetClipBox(rectClip); if (EqualRect(&rectClient, &rectClip)) { if (m_bWasCovered) { m_bWasCovered = false; this->Invalidate(true); } } else { m_bWasCovered = true; } if (!pDC->IsPrinting()) pDC->FillSolidRect(rectClip, RGB(204, 204, 204)); if (pModelDoc->Model()->IsValid()) pModelDoc->Model()->Draw(pDC, rectClip);
From: Scoots on 18 Nov 2009 18:11 My apologies, the last went out incomplete as my browser interpretted my formatting of the code (in which I dared to press spacebar) as clicking the "send" button in Google Groups. Many apologies. Now, it seems to me (though I am FAR from fluent in device contexts or even CViews in general (working on "inherited" code) ) that I should be able to create a CMemDC and tell it to draw on that. I know enough to know that the draw code shouldn't care the slightest WHAT it is drawing on, but I haven't been able to find information on how to set up drawing to a bitmap in memory. Seems relatively simple, do you think any of you can help me out? (apologies again on that last post, and I know the code cuts off, I wasn't done. But I think that shows the important stuff) Thanks ~Scoots
From: Scoots on 18 Nov 2009 18:15 Apologies again. It appears the CMemDC (which I saw elsewhere in the code) is a custom class that exists in the inherited code, and is pulled from I believe CodeProject. I'd like to know the REAL way to draw to a bitmap, since I don't to go through this custom class. Sorry for the several posts, I just felt I better address that. ~Scoots
From: AliR on 19 Nov 2009 11:10 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. AliR. "Scoots" <linkingfire(a)msn.com> wrote in message news:01f07cd9-e1c7-4c5a-a88d-0df93146b0a9(a)g27g2000yqn.googlegroups.com... > 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(); > ASSERT_VALID(pModelDoc); > > CDC *pDC = pDCWnd; > OnPrepareDC(pDC); > > theApp.m_mtxDrawInProgress.Lock(); > > CRect rectClient; > GetClientRect(&rectClient); > > > CRect rectClip; > pDCWnd->GetClipBox(rectClip); > > if (EqualRect(&rectClient, &rectClip)) > { > if (m_bWasCovered) > { > m_bWasCovered = false; > this->Invalidate(true); > } > } > else > { > m_bWasCovered = true; > } > > > > if (!pDC->IsPrinting()) > pDC->FillSolidRect(rectClip, RGB(204, 204, 204)); > > > if (pModelDoc->Model()->IsValid()) > pModelDoc->Model()->Draw(pDC, rectClip);
From: Scoots on 21 Nov 2009 19:34
The code referenced by Seetharam (with a little tweaking) worked wonderfully. I was unaware of the PrintWindow call. In fact, it actually works better than I thought. I was originally going to take a screenshot of each window and reconstruct. With this, I actually don't, though that's part of the way the application is built. There are no menus or titlebar, rather there is a eventbar CView that uses (for the most part) a button interface. I don't have to reconstruct to get this bar in, AND it excludes dialogs that I have opened up on top (which was actually a feature that I wanted) It's been some time since I worked with device contexts. I think I need to brush up a bit. Any recommended readings? ~Scoots |