Re: Details in PIZ compression

Unfortunately there isn't a document that describes PIZ (or any of the
other compression methods) in detail.  If anyone wants to write such a
description, I'd be happy to put it on the web site, along with the
other documentation.


Jack Mak wrote:
> Hi Florian,
> 
> Thanks for your explanation. I got the big picture. Before I look 
> through the source code, just wonder, are there any documents (papers, 
> standards...) give a detailed description of PIZ compression?
> 
> Best regards,
> 
> Jack
> 
> On Fri, Feb 22, 2008 at 2:39 PM, Florian Kainz <[email protected] 
> <mailto:[email protected]>> wrote:
> 
>     For the details of PIZ compression, you'll have to
>     look at the source code, but here's a brief overview:
> 
>     The image is split into blocks that are 32 pixels high
>     and as wide as the image.  The blocks are split into
>     individual channels.  The bit-patterns that comprise
>     the half values in each block are re-interpreted as
>     16-bit integers, and the integers are run through a
>     lookup table that shapes their distribution such that
>     comb-like histograms, with spikes separated by wide
>     gaps, are avoided.  A Haar wavelet transform is applied
>     to the output of the lookup table, and the output of
>     the wavelet transform is compacted using a 16-bit
>     Huffman coder.
> 
>     PIZ is mathematically lossless because each individual
>     step is reversible.  The wavelet transform is reversible
>     because it operates on integers and has no roundoff error.
> 
>     Florian
> 
> 
> 
>     Jack Mak wrote:
>      > Hi Experts,
>      >
>      > How does the PIZ compression work? Where can I find reference that
>      > discusses it in detail? (I checked out the documentations on the
>      > OpenEXR website, but they does not help.)
>      >
>      > Many thanks
>      >
>      > Jack
>      >
>      >
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>      >
> 
>