3. The method of claim 2 , wherein the computing of the affinity matrix includes: calculating a feature vector of an image that depicts the visual pattern; calculating vector distances between the visual pattern and other visual patterns in the reference set based on the feature vector; and including representations of the vector distances in the affinity matrix as quantifiers of similarity between the visual pattern and the other visual patterns.
2. The method of claim 1 , wherein the classifying of the reference set includes: computing an affinity matrix that quantifies degrees to which the visual patterns that belong to the parent class are similar to each other; and grouping the visual patterns into the mutually exclusive child classes by applying spectral clustering to the affinity matrix.