| 摘要 |
The invention concerns a device (D) for compressing digital image data by wavelet transform. Said device (D) comprises processing means (PM) provided with i) a module (M1) for transforming digital image data into wavelet coefficients distributed in sub-bands, ii) a module (M2) for estimating for each coefficient of each sub-band of the image, first and second sets of prediction parameters, associated respectively with so-called north-south and west-east directions, based on the values of wavelet coefficients of its north or south neighbours, iii) a module (M3) for quantifying the wavelet coefficients, and iv) an entropy coding module (M4) for determining for each coefficient of each sub-band of the image prediction values of expectation and of the width of a Laplace function representing its probability density, based on said first and/or second sets of prediction parameters and on the wavelet coefficient quantified by its north neighbour or its west neighbour, and for entropy coding of the wavelet coefficients quantified by means of specific associated expectations and widths. |
