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 [email protected] http://lists.nongnu.org/mailman/listinfo/openexr-user
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