A method is for compressing a digital image that is made up of a matrix of elements, with each element including a plurality of digital components of different types for representing a pixel. The method includes splitting the digital image into a plurality of blocks, and calculating for each block a group of DCT coefficients for the components of each type, and quantizing the DCT coefficients of each block using a corresponding quantization table scaled by a gain factor for achieving a target compression factor. The method further includes determining at least one energy measure of the digital image, and estimating the gain factor as a function of the at least one energy measure. The function is determined experimentally according to the target compression factor.