Dropbox, Inc.

Keith Winstein

Daniel R Horn

Ken Elkabany

Daniel Horn

Techniques for lossless compression of a digital image using prior image context.

Lossless decompression of digital images using prior image context

Lossless compression of digital images using prior image context

Techniques for image recompression. In one implementation, the techniques are implemented to recompress a baseline joint photographic experts group (JPEG) image with compression savings. The techniques replace the Huffman coding of baseline JPEG with an arithmetic coding that uses a sophisticated adaptive probability model. The arithmetic coding techniques avoid global operations such as global sorting that would prevent distributed and multithreaded decompression operations when recovering the original JPEG image from the recompressed image. At the same time, the techniques realize substantial compression savings relative to baseline JPEG, on average 23% compressing savings in some implementations.

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Palo Alto, CA, United States of America

Keith Winstein