[Imgcif-l] High speed image compression

[Herbert J. Bernstein]

Have you considered using cstdio and fwrite to write in large blocks?
That should take you close to the minimum time.
   -- Herbert


At 5:36 PM -0500 7/28/11, Justin Anderson wrote:
>Thanks Nicholas.
>
>I only made a couple small changes to Graeme's code.  1: to load an 
>image from a file and write to file and 2: to pass the data vectors 
>by reference.  The last change seems to have sped things up a little 
>but it's still taking 110 - 130 ms to compress which is too slow. 
>We are not as concerned with decompression speed as that will not 
>need to occur in real-time.
>
>I put on our FTP here: 
>ftp://ftp.rayonix.com/pub/del_in_30_days/byte_offset.tgz.
>
>Thanks,
>
>Justin
>
>On 7/28/11 2:06 PM, Nicholas Sauter wrote:
>>Justin,
>>
>>Just some comments based on our experience...first, I haven't tried the
>>compression extensively, just the decompression.  But I've found Graeme's
>>decompression code to be significantly faster than the CBF library, first
>>because it is buffer-based instead of file-based, and also because it
>>hard-codes some assumptions about data depth.
>>
>>I'd be happy to examine this in more detail if there is some way to share
>>your code example...
>>
>>Nick
>>
>>On Thu, Jul 28, 2011 at 11:46 AM, Justin Anderson<justin at rayonix.com>wrote:
>>
>>>Hello all,
>>>
>>>I have run Graeme's byte offset code on a 4k x 4k (2 byte depth) Gaussian
>>>noise image and found it to compress the image in around 150 ms (64-bit
>>>RHEL, Pentium D 3.46GHz).  Using CBF library with byte offset compression, I
>>>find the compression takes around 125 ms.
>>>
>>>This will be too slow to keep up with our high speed CCD cameras.  We are
>>>considering parallelizing the byte offset routine by operating on each line
>>>of the image individually.  Note that this would mean that a given
>>>compressed image would be stored differently than via the whole image
>>>algorithm.
>>>
>>>Has anyone been thinking about this already or does anyone have any
>>>thoughts?
>>>
>>>Regards,
>>>
>>>Justin
>>>
>>>--
>>>Justin Anderson
>>>Software Engineer
>>>Rayonix, LLC
>>>justin at rayonix.com
>>>1880 Oak Ave. #120
>>>Evanston, IL, USA 60201
>>>PH:+1.847.869.1548
>>>FX:+1.847.869.1587
>>>
>>>
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>>>
>>
>>
>
>
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-- 
=====================================================
  Herbert J. Bernstein, Professor of Computer Science
    Dowling College, Kramer Science Center, KSC 121
         Idle Hour Blvd, Oakdale, NY, 11769

                  +1-631-244-3035
                  yaya at dowling.edu
=====================================================