Re: Details in PIZ compression

If there were a rudimentary set of notes to start with ... I remember 
hearing it described in a seminar at SIGGRAPH a few years back, so I seem 
to recall it involves matrix transforms and so forth, but the rest is a 
bit fuzzy by now.

On Wed, 27 Feb 2008, Florian Kainz wrote:

> 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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>> 
>> 
>
>
>
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