Ahmad Zandi

Compression with reversible embedded wavelets with an enhanced binary mode

Compression with reversible embedded wavelets (CREW) is a unified lossless and lossy continuous-tone still image compression system. Wavelet coefficients are encoded in a bit-significance embedded order, allowing lossy compression by truncating the compressed data after encoding. CREWs context-based coding, called Horizon coding, takes advantage of the spatial and spectral information available in the wavelet domain and adapts well to the lessor significant bits. CREWs capabilities have been enhanced to include a binary mode for compression of binary and graphic images. This also improves compression on some images that do not use the full dynamic range. The binary mode encodes bit-planes of the image without using the transform. This JBIG-like system uses the resources already available in the CREW system. This paper introduces some basic concepts of CREW and describes the binary mode in detail.

Device selective quantization for reversible wavelets

Compression with reversible embedded wavelets (CREW) consists of three major parts: a wavelet transform, an embedded context model, and a binary entropy coder. The wavelet transform is a special implementation of high quality wavelet which provides perfect reconstruction with finite precision coefficients. The context model describes the wavelet coefficients in a particular order with conditional probability estimates. Finally the FSM-coder, a binary entropy coder with functionality similar to the QM-coder, is used to generate the final code stream.