{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:37:37Z","timestamp":1760240257383,"version":"build-2065373602"},"reference-count":21,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2019,4,22]],"date-time":"2019-04-22T00:00:00Z","timestamp":1555891200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In the field of Facial Expression Recognition (FER), traditional local texture coding methods have a low computational complexity, while providing a robust solution with respect to occlusion, illumination, and other factors. However, there is still need for improving the accuracy of these methods while maintaining their real-time nature and low computational complexity. In this paper, we propose a feature-based FER system with a novel local texture coding operator, named central symmetric local gradient coding (CS-LGC), to enhance the performance of real-time systems. It uses four different directional gradients on 5 \u00d7 5 grids, and the gradient is computed in the center-symmetric way. The averages of the gradients are used to reduce the sensitivity to noise. These characteristics lead to symmetric of features by the CS-LGC operator, thus providing a better generalization capability in comparison to existing local gradient coding (LGC) variants. The proposed system further transforms the extracted features into an eigen-space using a principal component analysis (PCA) for better representation and less computation; it estimates the intended classes by training an extreme learning machine. The recognition rate for the JAFFE database is 95.24%, whereas that for the CK+ database is 98.33%. The results show that the system has advantages over the existing local texture coding methods.<\/jats:p>","DOI":"10.3390\/s19081899","type":"journal-article","created":{"date-parts":[[2019,4,22]],"date-time":"2019-04-22T11:02:53Z","timestamp":1555930973000},"page":"1899","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Improved Real-Time Facial Expression Recognition Based on a Novel Balanced and Symmetric Local Gradient Coding"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5046-2663","authenticated-orcid":false,"given":"Jucheng","family":"Yang","sequence":"first","affiliation":[{"name":"College of Computer Science and Information Engineering, Tianjin University of Science and Technology, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiaojing","family":"Wang","sequence":"additional","affiliation":[{"name":"College of Computer Science and Information Engineering, Tianjin University of Science and Technology, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shujie","family":"Han","sequence":"additional","affiliation":[{"name":"College of Computer Science and Information Engineering, Tianjin University of Science and Technology, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jie","family":"Wang","sequence":"additional","affiliation":[{"name":"College of Computer Science and Information Engineering, Tianjin University of Science and Technology, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dong Sun","family":"Park","sequence":"additional","affiliation":[{"name":"College of Computer Science and Information Engineering, Tianjin University of Science and Technology, Tianjin 300457, China"},{"name":"Department of Electronic and Information Engineering, Chonbuk National University, Jeonbuk 561-756, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuan","family":"Wang","sequence":"additional","affiliation":[{"name":"College of Computer Science and Information Engineering, Tianjin University of Science and Technology, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,4,22]]},"reference":[{"unstructured":"Mehrabian, A. 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