A moving-image signal, such as typically a luminance signal organized in blocks of pixels is coded via a technique that envisages the steps of: comparing a block to be coded with a plurality of candidate prediction blocks; determining, for each candidate prediction block, a respective value of an index representing the difference between the block to be coded and each candidate prediction block; and choosing between the candidate prediction blocks, as a function of the respective value of the aforesaid index, a prediction block to be used for coding of the block to be coded. The signal is sampled pixel by pixel on the block to be coded and on the plurality of candidate prediction blocks, thus generating respective surfaces representing the pattern of the signal in the block to be coded and in the candidate prediction blocks. Chosen as an index is an index of the parallelism between the aforesaid respective surfaces.