1. A method of chromatic classification of pixels of a digital image comprising the steps of: transforming a chromatic domain of definition of pixels from a three-dimensional space into a respective two-dimensional normalized space; defining a reference model of classification by analyzing a plurality of images of distinct types of subjects, generating distinct collections of samples with respective coordinates in the normalized two-dimensional space for each of a number of chromatic classes corresponding to real subjects; and evaluating for each image pixel to be classified a membership class and a membership level based on the reference model; wherein said reference model is defined by a parametric membership function continuous on said normalized two-dimensional space for each of said classes, parameters of which are determined by processing the collection of two-dimensional samples of each of said classes.