Luciano Alparone Univ. di Firenze (Italy) Paolo Capperi Univ. of Florence (Italy) Bruno Aiazzi CNR (Italy) Stefano Baronti IROE-CNR (Italy) Giuliano Benelli Univ. di Siena (Italy)
An extension of the reduced-difference pyramid (RDP) algorithm is derived and proposed for lossy image compression with upperbounded maximum error (semilossy). Quantization has been introduced into the basic RDP in two different ways: approximations are made either before or after taking the differences among pairs of adjacent nodes. The resulting peak-error (PE) propagation along the pyramid is theoretically investigated, and quantization strategies are suggested. Tests on the standard gray-scale Lena image show significant and steady rate-distortion improvements over the original RDP. As few fixed-point operations are required per pixel, on-line compression/decompression is feasible on general-purpose computers.