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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.
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what do you mean "old" and "new" BitBlt ?
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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.
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Yes, I know redraw picture is a time-costing work.
But, the application need to update picture with the real-time data.
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I do real-time drawing... bitblt() is your friend, you're probably doing something else that's slow.
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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?
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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).
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How much time does it take to do the other 4 lines?
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It seems 1-3 ms, based on tickcount() result
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Do you handled CDC::SetStretchBltMode[^] ? Depend on this settings, you will have rendering speed or render quality ...
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Thanks, I will read descriptions of this function
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Hey why not using DirectX ,it uses Double buffering algorithm
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Thanks,image without dirctx components inside
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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. 
modified 2-Feb-15 18:09pm.
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Hi, I have a question, situation like:
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.
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What exactly are you trying to achieve?
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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.
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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.
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Thanks, have not try it.
Just thinking if the way is reasonable.
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Trying things is the best way to learn.
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Hi,I wonder how a bitblt function of a CDC object, which src is a HDC object?
like:
MemDC.BitBlt(Icon.pos_x, Icon.pos_y, bm.w, bm.h,HdcObject,0,0,SRCCOPY);
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Quote: which src is a HDC object?
What? That doesn't make sense. Try rephrasing or expand on what you're trying to ask.
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I mean HdcObject in the code.
I just want to copy a HDC object to CDC object, use CDC object's BitBlt() function.
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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.
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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 
Thanks in advance for any idea, I'm desperate, unable to create even an empty Win32 project !
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