Re: BitBlt() function performance question - C / C++ / MFC Discussion Boards

Re: BitBlt() function performance question

Albert Holguin25-Jan-15 8:19

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.

Re: BitBlt() function performance question

econy26-Jan-15 3:50

econy

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.

Re: BitBlt() function performance question

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.

Re: BitBlt() function performance question

econy26-Jan-15 5:07

econy

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?

Re: BitBlt() function performance question

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).

Re: BitBlt() function performance question

enhzflep25-Jan-15 14:26

enhzflep

25-Jan-15 14:26

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

Re: BitBlt() function performance question

econy26-Jan-15 3:51

econy

26-Jan-15 3:51

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

Re: BitBlt() function performance question

_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 ...

Re: BitBlt() function performance question

econy26-Jan-15 3:48

econy

26-Jan-15 3:48

Thanks, I will read descriptions of this function

Re: BitBlt() function performance question

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

Re: BitBlt() function performance question

econy27-Jan-15 7:18

econy

27-Jan-15 7:18

Thanks,image without dirctx components inside

Re: BitBlt() function performance 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.

CompatibleDC parameter question

econy23-Jan-15 4:36

econy

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.

Re: CompatibleDC parameter question

Richard MacCutchan23-Jan-15 5:35

Richard MacCutchan

23-Jan-15 5:35

What exactly are you trying to achieve?

Re: CompatibleDC parameter question

econy23-Jan-15 5:52

econy

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.

Re: CompatibleDC parameter question

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.

Re: CompatibleDC parameter question

econy23-Jan-15 6:38

econy

23-Jan-15 6:38

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

Re: CompatibleDC parameter question

Richard MacCutchan23-Jan-15 6:45

Richard MacCutchan

23-Jan-15 6:45

Trying things is the best way to learn.

CDC bitblt function with HDC parameter?

econy23-Jan-15 4:17

econy

23-Jan-15 4:17

Hi,I wonder how a bitblt function of a CDC object, which src is a HDC object?
like:

C++

MemDC.BitBlt(Icon.pos_x, Icon.pos_y, bm.w, bm.h,HdcObject,0,0,SRCCOPY);

Re: CDC bitblt function with HDC parameter?

Albert Holguin23-Jan-15 4:28

Albert Holguin

23-Jan-15 4:28

Quote:
which src is a HDC object?

What? That doesn't make sense. Try rephrasing or expand on what you're trying to ask.

Re: CDC bitblt function with HDC parameter?

econy23-Jan-15 4:38

econy

23-Jan-15 4:38

I mean HdcObject in the code.

I just want to copy a HDC object to CDC object, use CDC object's BitBlt() function.

Re: CDC bitblt function with HDC parameter?

Albert Holguin23-Jan-15 5:15

Albert Holguin

23-Jan-15 5:15

HDC is a handle not an object....

You can use CDC::FromHandle() to get a temporary object for immediate use. Alternatively, you can CDC::Attach() to keep a more permanent CDC object around. You should make sure you release a device context (DC) when you're done using it (FromHandle sort of automatically handles this situation by going out of scope).

If you have CWnds, you can also get a pointer to an existing CDC with CWnd::GetDC().

There is a lot of info on drawing in GDI online, I suggest you read up on it.

""Object reference not set to an instance of an object" when creating new project with VS

jeff623-Jan-15 0:04

jeff6

23-Jan-15 0:04

Hello, I get this error when I try to create a new project wi h Visual Studio 2010 (XP), Win32, MFC or Forms (only VB works)

"Object reference not set to an instance of an object"

I found nothing with Google for this case (just creating a new project) and tried to uninstall/install, repair, n times, impossible to fix Frown | :-(

Thanks in advance for any idea, I'm desperate, unable to create even an empty Win32 project !

Re: ""Object reference not set to an instance of an object" when creating new project with VS

Richard MacCutchan23-Jan-15 0:57

Richard MacCutchan

23-Jan-15 0:57

Looks like a Visual Studio problem, but impossible to guess what.

Re: ""Object reference not set to an instance of an object" when creating new project with VS

jeff623-Jan-15 1:16

jeff6

23-Jan-15 1:16

But it appeared just recently, it had worked for years before

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.