C / C++ / MFC

23-Jan-15 7:55

Hi, in a windows CE platform, I tested BitBlt() function,
I found it will take about 400 millisecdons to do:

MemBoard.CreateCompatibleDC(&dc);
bmpDashBoard.LoadBitmap( IDB_SCREEN_IMP );
pOldBmp = (CBitmap*)Memboard.SelectObject(&bmpBoard);
...
MemDC.CreateCompatibleDC(dc);
..
MemDC.BitBlt(0,0, 800,600,&Memboard, 0, 0, SRCCOPY);

is there anyway to speed up BitBlt() function?

image processing toolkits | batch image processing

C^hris L^osinger23-Jan-15 10:39

C^hris L^osinger

23-Jan-15 10:39

are you saying it takes 400ms to do all of that, or just the BitBlt?

because you can do the LoadBitmap ahead of time and just keep the CBitmap around for when you need it.

econy23-Jan-15 13:38

23-Jan-15 13:38

I can't get precise time, but, with old BitBlt(), not a 800*600 bitmap,
I set tick count array in program, tkCount[15]-tkCount[14] = tkCount[14] - tkCount[13] ... = tkCount[1] - tkCount[0] = 170 ms around.

Then I use new BitBlt() to load 800*600 bitmap, it gives 400ms around.

So I should say it added 230 ms.

Old BitBlt() just transport about 1/5 or 1/6 part of 800*600 bitmap.

I expected to use a 800*600(the screen area) memory DC to hold all parts changes, then BitBlt() to screen.

Now that 800*600 tooks so much time, I don't think a double buffer technique is helpful.

image processing toolkits | batch image processing

C^hris L^osinger27-Jan-15 1:59

C^hris L^osinger

27-Jan-15 1:59

what do you mean "old" and "new" BitBlt ?

Albert Holguin25-Jan-15 8:19

Albert Holguin

25-Jan-15 8:19

I doubt it's the BitBlt slowing you down that much. You probably shouldn't be loading a bitmap every single time, load it once and keep it in memory for better results.

econy26-Jan-15 3:50

26-Jan-15 3:50

Yes, I know redraw picture is a time-costing work.
But, the application need to update picture with the real-time data.

Albert Holguin26-Jan-15 4:00

Albert Holguin

26-Jan-15 4:00

I do real-time drawing... bitblt() is your friend, you're probably doing something else that's slow.

econy26-Jan-15 5:07

26-Jan-15 5:07

The background picture is 800*600, 24 color depth, so it is about 1.44 MB.
Did you think the picture size would affect the BitBlt() speed?

Albert Holguin26-Jan-15 6:34

Albert Holguin

26-Jan-15 6:34

I'm sure it would... but not to the extent that your numbers reflect. You're doing something else wrong (or... more precisely, you're doing something else that's slowing the process down).

enhzflep25-Jan-15 14:26

enhzflep

25-Jan-15 14:26

How much time does it take to do the other 4 lines?

econy26-Jan-15 3:51

26-Jan-15 3:51

It seems 1-3 ms, based on tickcount() result

_Flaviu25-Jan-15 21:12

_Flaviu

25-Jan-15 21:12

Do you handled CDC::SetStretchBltMode[^] ? Depend on this settings, you will have rendering speed or render quality ...

econy26-Jan-15 3:48

26-Jan-15 3:48

Thanks, I will read descriptions of this function

Nitin K. Kawale26-Jan-15 17:36

Nitin K. Kawale

26-Jan-15 17:36

Hey why not using DirectX ,it uses Double buffering algorithm

econy27-Jan-15 7:18

27-Jan-15 7:18

Thanks,image without dirctx components inside

CompatibleDC parameter question

Mike Nordell2-Feb-15 9:44

Mike Nordell

2-Feb-15 9:44

If it's indeed the blit sucking that much time, prime suspect would be format conversion.

Check out GetObject() for BITMAP, to see what the format of src and dest are. I'm willing to bet 3 lines of C++ that they are different. Smile | :)

modified 2-Feb-15 18:09pm.

econy23-Jan-15 4:36

23-Jan-15 4:36

Hi, I have a question, situation like:

C++

void funcA() 
{
   CDC	MemDC;
   CDC	*pDC ;
   pDC = GetDC(); 
   memDC.CreateCompatibleDC(pDC);
   
   funcB(memDC);
}

void funcB(CDC *pDC) 
{
   HDC hdc;
   HDC hdcMem;

   hdc = pDC->m_hDC;
   hdcMem = CreateCompatibleDC(hdc);
   ...
   BitBlt(hdc,0,0,100,100,hdcMem,0,0,SRCCOPY);
}

I think this BitBlt() will copy hdcMem to MemDC(in FuncA), right? just want to confirm it.

Richard MacCutchan23-Jan-15 5:35

Richard MacCutchan

23-Jan-15 5:35

What exactly are you trying to achieve?

econy23-Jan-15 5:52

23-Jan-15 5:52

I want funcB draw picture on it's own temporary DC, then paste on funcA's memory DC, and FuncA paste the whole funcA's DC to screen.

Like:
B -> A
c -> A
...
x -> A

and A -> screen.

And I had another question, I have a big bitmap, represent the screen, many parts of the bitmap need to update independently and frequently.

is it a good idea using one memory DC to hold
all part's temporary DC, then post the whole memory DC to screen? that is, the double buffering technique.

Richard MacCutchan23-Jan-15 6:32

Richard MacCutchan

23-Jan-15 6:32

1. Sounds OK. What happens when you try it?
2. Yes, keeping a MemDC with all the information and then updating that, before blitting to screen is probably the best way.

econy23-Jan-15 6:38

23-Jan-15 6:38

Thanks, have not try it.
Just thinking if the way is reasonable.

CDC bitblt function with HDC parameter?

Richard MacCutchan23-Jan-15 6:45

Richard MacCutchan

23-Jan-15 6:45

Trying things is the best way to learn.

econy23-Jan-15 4:17