Method for encoding a matrix, in particular a matrix representative of a still or video image, using a wavelet transform, with numbers of wavelet levels that vary according to the image and different quantization factors for each wavelet level

Method for compressing a digital image including a step of encoding, in successive layers, an initial matrix as a compressed matrix and restoration thereof as a restored matrix, each cell of the initial matrix containing a respective initial numeric value;

• each cell of the compressed matrix containing a respective compressed numeric value corresponding to the respective initial numeric value;
• each cell of the restored matrix containing a respective restored numeric value corresponding to the respective initial numeric value;
• characterized in that, in order to encode, i.e. compress the initial matrix, the following is applied:
• wavelet transformations applied to the entire image over a limited number of levels, so that there is a residual level with dimensions greater than 2×2;
• then,
• differential encoding of the residual level, including, for a cell of the residual level having a respective initial value, the calculation of the corresponding respective compressed value on the basis of a difference between said respective initial value and the respective restored value of a cell of the residual level.