Face emotions analysis is one of the fundamental techniques that might be exploited in a natural human-computer interaction process and thus is, one of the most studied topics in current computer vision literature. In consequence face features extraction is an indispensable element of the face emotion analysis as it influences decision making performance. The paper concentrates on mouth features extraction, which next to eye region features becomes one of the most representative face regions in the context of emotions retrieval. In the paper original, gradient based, mouth features extraction method was presented. Its high performance (exceeding 90% for selected features) was also verified for a subset of the Yale images database.
Staniucha, R., & Wojciechowski, A. (2017). Mouth features extraction for emotion analysis. In Advances in Intelligent Systems and Computing (Vol. 534, pp. 228–237). Springer Verlag. https://doi.org/10.1007/978-3-319-48429-7_21