LAUSR

This letter introduces a novel grayscale-inversion and rotation invariant descriptor, called sorted local gradient pattern, for texture classification. First, we propose two complementary local gradient patterns (LGP), the center-to-ring LGP (LGP_CR) and the ring-to-ring LGP (LGP_RR), to encode rich gradient information present in a local neighborhood. Then, we propose to enhance LGP by encoding pixels’ intensity information. This is achieved by sorting image pixels into two categories via a dominant intensity order measure, followed by extracting LGP features over the categorized pixels. As a result, local gradient information and global intensity order information are both encoded into our descriptor in a way that is robust to grayscale-inversion and rotation changes. Experiments on three texture databases demonstrate that the proposed descriptor achieves state-of-the-art classification results in the presence of linear and even nonlinear grayscale-inversion changes.