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This software package contains an implementation of JPEG-LS, the emerging
lossless/near-lossless compression standard for continuous-tone images being
developed by ISO/IEC JTC1/SC29/WG1 (draft document FCD14495 as of November
1997). The names of the executables in the software package derive from the
acronym LOCO, as the core of the new standard is based on the LOCO-I algorithm
(LOw COmplexity LOssless COmpression for Images) developed at Hewlett-Packard
Laboratories (reference: M. Weinberger, G. Seroussi, G. Sapiro, "LOCO-I: A Low
Complexity, Context-Based, Lossless Image Compression Algorithm," Proc. IEEE
Data Compression Conference, Snowbird, Utah, March-April 1996).
The term "near-lossless compression" refers to a lossy algorithm for which each
decompressed image sample differs from the corresponding original image sample
by not more than a pre-specified value, the (usually small) "loss." Lossless
compression corresponds to loss=0. Even though the term "continuous-tone image"
refers in principle to any image whose components have more than one bit per
sample, palletized images may require a reordering of the color palette for best
compression results using LOCO-I on the array of color indices. This
functionality is not implemented in the present software, although it is
supported by the new standard, and is easy enough to implement with the tools
given. Notice, however, that LOCO-I and JPEG-LS were not designed, and might not
give optimal performance, for images that have been palletized through
dithering.
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