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From: | Jack Mak |
Subject: | Re: [Openexr-user] Details in PIZ compression |
Date: | Wed, 27 Feb 2008 10:37:57 -0800 |
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
>
>
> Openexr-user mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/openexr-user
>
>
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