An encoding method for encoding successive layers of an initial matrix into a compressed matrix and restoring it as a restored matrix, each cell of the initial matrix containing a respective initial numerical value; each cell of the compressed matrix containing a respective compressed numerical value corresponding to the respective initial numerical value; each cell of the restored matrix containing a respective restored numerical value corresponding to the respective initial numerical value; is characterized in that to encode, one applies: —wavelet transforms applied to the entire matrix over a limited number of levels, such that a residual level remains with dimensions larger than or equal to 2×2; then, a differential encoding of the residual level, i.e., a compression of the residual level by obtaining differences with each of the values of the residual level.