Re: Bitblt() is faster then SetDIBitsToDevice()?

From:

asm23 <asmwarrior@gmail.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Mon, 22 Sep 2008 11:07:01 +0800

Message-ID:

<gb722q$l6p$1@news.cn99.com>

Joseph M. Newcomer wrote:

No, I mean that you do something like

LARGE_INTEGER start;
::QueryPerformanceCounter(&start);
... do computation
::QueryPerformanceCounter(&end);

LONGLONG delta = end.QuadPart - start.QuadPart;

do this for two different algorithms (you said you had already written them, so
instrumenting them requires the four lines above!) Look at the results. Make several
measurements and average them, of course.

You can convert the delta from relative information to absolute time by using the value
from QueryPerformanceFrequency.

It has nothing to do with source code or the device manufacturer. It has to do with
actually MEASURING the information you want to get, instead of trying to depend on
"secondary sources" such as Microsoft documentation or "opinions" not backed by actual
measurement information.
joe

Thanks joe!
I have test My code in these two method. And that's the CTimer class I use.
/////////////////////////////////////////////////////
class CTimer
{
private:

    LARGE_INTEGER m_base;
    LARGE_INTEGER m_temp;
    float m_resolution;

public:

    CTimer::CTimer()
    {
        LARGE_INTEGER t_freq;
        QueryPerformanceFrequency(&t_freq);
        m_resolution = (float) (1.0f / (double) t_freq.QuadPart);
        reset();
    }

    void CTimer::reset()
    {
        QueryPerformanceCounter(&m_base);
    }

    inline float time() {
        QueryPerformanceCounter(&m_temp);
        return (m_temp.QuadPart - m_base.QuadPart) * m_resolution * 1000.0f;
    }

};
////////////////////////////////////////////////////////
This is the result on my system:

method 1 (using SetDIBitsToDevice())
     the average of painting a 656*490 24bit image is : 1.63ms
method 2 (using bitblt()
     the average painting time is : 1.64ms

So, I think they are just in the same speed.^_^.