Extended 3D HLAC pattern features for solid textures

Higher order local autocorrelation (HLAC) features are used in various 2D image applications. Recent three dimensional extensions of HLAC features (3D HLAC) have made possible the analysis of solid textures including solid textures. Typically, 3D HLAC features are computed by a limited number of three dimensional mask patterns, and the order of the mask patterns is limited up to the second order. In this paper, the orders of the mask patterns are increased up to the 26th order. Since there are a large number of combinations of mask patterns, we have implemented a simulation program for finding all their combinations in a systematic manner. Also the various subsets of the 3D HLAC mask patterns are computed by limiting the displacement regions of the masks. The 3D HLAC features were computed as local features rather than global features, and the bag of features (BoF) approach was applied for comparing local features. Our experimental program extracted pattern features from solid textures by using the extended 3D HLAC mask patterns. In our preliminary experiments, databases of solid textures were synthesized from 2D images. A similarity retrieval system for the solid textures has been implemented, and its extension to the 3D HLAC features performed well in retrievals.