Compression of partially-masked image data

摘要

Wavelet coding of partially-masked image information may be made faster by either of two embodiments of the present invention. In a first embodiment, quick convergence is obtained by performing wavelet encoding in stages, each stage associated with a predetermined wavelet scale. Each stage comprises a low-pass filter (110) and a high-pass linear filter (120). By advancing the stages from finest scale to coarsest scale, coefficients of the masked wavelets are identified early in the coding process. In a second embodiment, quick convergence is obtained by introducing overshoot techniques when masked coefficients are identified, modified and image data is reconstructed therefrom.