HP Labs Technical Reports
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The LOCOI Lossless Image Compression Algorithm: Principles and Standardization into JPEGLS
Weinberger, Marcelo; Seroussi, Gadiel; Sapiro, Guillermo
HPL98193
Keyword(s): lossless image compression; standards; Golomb codes; geometric distribution; context modeling; near lossless compression
Abstract: LOCOI (LOw COmplexity LOssless COmpression for Images) is the algorithm at the core of the new ISO/ITU standard for lossless and nearlossless compression of continuoustone images, JPEGLS. It is conceived as a "low complexity projection" of the universal context modeling paradigm, matching its modeling unit to a simple coding unit. By combining simplicity with the compression potential of context models, the algorithm "enjoys the best of both worlds". It is based on a simple fixed context model, which approaches the capability of the more complex universal techniques for capturing highorder dependencies. The model is tuned for efficient performance in conjunction with an extended family of Golombtype codes, which are adaptively chosen, and an embedded alphabet extension for coding of lowentropy image regions. LOCOI attains compression ratios similar or superior to those obtained with stateof theart schemes based on arithmetic coding. Moreover, it is within a few percentage points of the best available compression ratios, at a complexity level estimated at an order of magnitude lower. We discuss the principles underlying the design of LOCOI , and its standardization into JPEGLS.
31 Pages
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