Mathematical morphology has shown to be an effective tool to extract spatial information for remote-sensing image classification. Its application is performed by means of a structuring element (SE), whose shape and size play a fundamental role for appropriately extracting structures in complex regions such as urban areas. In this letter, we propose a novel method, which automatically tailors both the shape and the size of the SE according to the considered classification task. For this purpose, the SE design is formulated as an optimization problem within a particle swarm optimization framework. The experiments conducted on two real images suggest that better accuracies can be achieved with respect to the common procedure for finding the best regular SE, which, so far, is heuristically done.

Wavelets are known to be a valuable tool for analyzing hyperspectral images. In this letter, we propose to further improve their performance by means of a novel classification-driven design scheme that aims at deriving a wavelet that best represents in terms of between-class discrimination capability the spectral signatures conveyed by a given hyperspectral image. This is achieved by adopting a polyphase representation of the wavelet filter bank and formulating the wavelet optimization problem within a particle-swarm-optimization (PSO) framework. Experimental results show that the proposed wavelet design method outperforms the popular Daubechies wavelets whatever the classifier type adopted in the classification process.