Speeding up Bitmaps Loading

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Speeding up Bitmaps Loading

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Speeding up Bitmaps Loading

Postby Perlom » Sat, 19 Jun 2004 00:20:03 GMT 

I am trying to load a sequence of large bitmaps (720*486) and then loop thru
each pixel and convert its color space form RGB to YCbCr which is used in TV
broadcasting. I'm using VB.NET.  Unfortunately, the overall process came up
to be real slow specially when running this on 300 frames (around 3
minutes).  The steps are:

 - Loop thru al files to load each bitmap:
        Dim mBitmap as Bitmap = Bitmap.FromFile(FileName(i))

 - Loop thru each pixel, get the color, and apply mathematical conversion
        For J = 0 to mBitmapHeight
            For K = 0 to mBitmapWidth
                  mColor = mBitmap.GetPixel(K,J)
                  Y = (Some math function involving R,G,B Values)
                  Cb= (Some math function involving R,G,B Values)
                  Cr= (Some math function involving R,G,B Values)
                  mFile.Write( values)
              Next
         Next

After doing some analysis, I found that the bottle nock is loading the
Bitmap step.  I am wondering if there any faster way to load a Bitmap. I
read on the MSDN site about Cashed Bitmaps, but I wasn't able to find an
example.  Anybody has a suggestion? Thanks in advance.

Kind Regards.
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Re: Speeding up Bitmaps Loading

Postby Philip Taylor [ATI] » Sat, 19 Jun 2004 01:15:13 GMT 

load it as a DirectX texture, and access it that way, since GDI based access
are usually slower than DX accesses.

this requires you to understand the texture format to such a level of detail
you dont have to depend on GDIs format conversion, which is usually the slow
part.

if its really just the file access thats the bottleneck, than DX cant help
you much and this forum isnt the right place to ask.





thru
TV
up
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Re: Speeding up Bitmaps Loading

Postby Perlom » Sun, 20 Jun 2004 00:25:25 GMT 

Thanks Phillip for the Info.  Can you direct me to where I can find few
samples about the method you suggested, or to which forum I should ask?

kind regards.


"Philip Taylor [ATI]" < XXXX@XXXXX.COM > wrote in


access
detail
slow



in
conversion
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Re: Speeding up Bitmaps Loading

Postby Shaun Pudwell » Sun, 20 Jun 2004 21:29:09 GMT 

I would have thought it would be better to create a C++ DLL to do the work
as processing a double loop like that in VB is going to be abysmally slow.







help



loop
came
I
an
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Re: Speeding up Bitmaps Loading

Postby Phil Taylor » Sat, 26 Jun 2004 01:23:32 GMT 

doesnt one of the SDK samples lock the texture and access the bits?

grep the samples on lock.






help



loop
came
I
an
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Similar Threads:

1.Speed of bitmaps 

Hi,

I am doing some time-critical work with bitmaps (a remote desktop monitoring
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1. After taking a screenshot of the desktop, I have a device-dependant
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2. What is the fastest way to get access to the bitmap so that it can be
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-- 
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2.Help with loading bitmaps 

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"DigitalDragon" < XXXX@XXXXX.COM > wrote in message
news:c7gkdh$l32$ XXXX@XXXXX.COM ...
>>
>>This question has probably been asked dozens of times,
>>but I'm a newie.  So, I'm wondering if there is an alternative
>>to the "auxDIBImageLoad()" function??
>>
>>I need a function that will load a bitmap stored in an
>>applications resources or resource script.  Does such
>>a function exist? (BTW, I'm using VisualC++ 6.0)
>
>
> i suggest you make your own loading function, it's a very simple format.
>

Ok!  I checked glaux.h header file, and I found the definition of
an "AUX_RGBImageRec" structure.  auxDIBImageLoad() returns
a pointer to this structure.  It looks like this :

typedef struct _AUX_RGBImageRec {
    GLint sizeX, sizeY;
    unsigned char *data;
} AUX_RGBImageRec;

So, after I read my bitmap from a resource script, I need to
store the bitmap bips in the "data" field??  Is that right?
And, I'm guessing that the sizeX and sizeY fields store the
bitmap dimensions??

Can anybody recommend a simple algorithm or an easy
win32 function that will load a bitmap into the "data" field?

thanks!

---------
S

4.Loading texture bitmaps! 

This question has probably been asked dozens of times,
but I'm a newie.  So, I'm wondering if there is an alternative
to the "auxDIBImageLoadA()" function??

I need a function that will load a bitmap stored in an
applications resources or resource script.  Does such
a function exist?

(BTW, I'm using VisualC++ 6.0)

Thanks!

--------
S

5.Loading bitmaps to use in texturing 

Hello,
Can anyone guide me to a library that can load a bitmap to use in
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leaks.

Thanks in advance,

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