A new embedded lossless/quasi-lossless image coder based on the Hadamard transform
This paper presents a lossless block-transform coder based on the Hadamard transform that achieves a compression ratio which is as good as that of the current lossless JPEG-standard and about 10 to 20% lower than the currently best state-of-the-art technique Calic. The main advantage of the proposed technique is that it produces an embedded data stream which may be truncated to achieve lossy compression. Preliminary results obtained on the "lena" image show that, at compression ratios up to 10, the proposed scheme (somewhat surprisingly) produces a better image quality (both visually and in terms of rms error) than lossy JPEG. This means that the proposed coder performs well over a wide range of compression ratios and is therefore a useful alternative for the lossy and lossless JPEG-standards in nearly-lossless coding or when lossless and lossy decoding must be supported simultaneously. Finally, the transform part of the proposed scheme requires fewer computations than lossy JPEG (and only slightly more than lossless JPEG).