1. A method for block-encoding of a raster image of pixels of multiple separate blocks, comprising: successive two-dimensional decompositioning of the blocks of the image in a base of discrete functions predetermined using a combined application of a one-dimensional kernel for vertical decomposition of n pixels and a one-dimensional kernel for horizontal decomposition of p pixels, wherein the horizontal direction of the blocks is defined as that of lines of the raster image in a line-by-line sequential read mode and/or transmission mode of the raster image; wherein the horizontal dimension P as a number of pixels of each block is determined as a multiple of p, P=k·p, and a decomposition at log p (P) level(s) of resolution is accomplished using the one-dimensional horizontal decomposition kernel; and wherein the vertical dimension N as a number of pixels of each block is determined as a multiple of n, N=l·n, and a decomposition at log n (N) level(s) of resolution is accomplished using the one-dimensional vertical decomposition kernel, and for given values of n and p, the values of k and l are chosen such that the vertical dimension N is strictly less than the horizontal dimension P.