local gradient pattern - a novel feature representation for facial expression recognition

many researchers adopt local binary pattern for pattern analysis. however, the long histogram created by local binary pattern is not suitable for large-scale facial database. this paper presents a simple facial pattern descriptor for facial expression recognition. local pattern is computed based on local gradient flow from one side to another side through the center pixel in a 3x3 pixels region. the center pixel of that region is represented by two separate two-bit binary patterns, named as local gradient pattern-lgp for that pixel. lgp pattern is extracted from each pixel. facial image is divided into 81 equal sized blocks and the histograms of local lgp features for all 81 blocks are concatenated to build the feature vector. experimental results prove that the proposed technique along with support vector machine is effective for facial expression recognition.