{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,3]],"date-time":"2026-06-03T13:16:27Z","timestamp":1780492587081,"version":"3.54.1"},"reference-count":20,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2025,8,11]],"date-time":"2025-08-11T00:00:00Z","timestamp":1754870400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Postgraduate Education Innovation Program of Shanxi Province","award":["2024SJ268"],"award-info":[{"award-number":["2024SJ268"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. Imaging"],"abstract":"<jats:p>In order to meet the high-precision location requirements of the corneal Placido ring edge in corneal topographic reconstruction, this paper proposes a sub-pixel edge detection algorithm based on multi-scale and multi-position enhanced Mexican Hat Wavelet Transform and improved Zernike moment. Firstly, the image undergoes preliminary processing using a multi-scale and multi-position enhanced Mexican Hat Wavelet Transform function. Subsequently, the preliminary edge information extracted is relocated based on the Zernike moments of a 9 \u00d7 9 template. Finally, two improved adaptive edge threshold algorithms are employed to determine the actual sub-pixel edge points of the image, thereby realizing sub-pixel edge detection for corneal Placido ring images. Through comparison and analysis of edge extraction results from real human eye images obtained using the algorithm proposed in this paper and those from other existing algorithms, it is observed that the average sub-pixel edge error of other algorithms is 0.286 pixels, whereas the proposed algorithm achieves an average error of only 0.094 pixels. Furthermore, the proposed algorithm demonstrates strong robustness against noise.<\/jats:p>","DOI":"10.3390\/jimaging11080267","type":"journal-article","created":{"date-parts":[[2025,8,11]],"date-time":"2025-08-11T11:02:09Z","timestamp":1754910129000},"page":"267","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Placido Sub-Pixel Edge Detection Algorithm Based on Enhanced Mexican Hat Wavelet Transform and Improved Zernike Moments"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0009-0009-2732-1991","authenticated-orcid":false,"given":"Yujie","family":"Wang","sequence":"first","affiliation":[{"name":"School of Information and Communication Engineering, North University of China, Taiyuan 030051, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jinyu","family":"Liang","sequence":"additional","affiliation":[{"name":"School of Information and Communication Engineering, North University of China, Taiyuan 030051, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yating","family":"Xiao","sequence":"additional","affiliation":[{"name":"School of Information and Communication Engineering, North University of China, Taiyuan 030051, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xinfeng","family":"Liu","sequence":"additional","affiliation":[{"name":"School of Information and Communication Engineering, North University of China, Taiyuan 030051, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiale","family":"Li","sequence":"additional","affiliation":[{"name":"School of Information and Communication Engineering, North University of China, Taiyuan 030051, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guangyu","family":"Cui","sequence":"additional","affiliation":[{"name":"School of Information and Communication Engineering, North University of China, Taiyuan 030051, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9867-2443","authenticated-orcid":false,"given":"Quan","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Information and Communication Engineering, North University of China, Taiyuan 030051, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,8,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"751","DOI":"10.1364\/OPTCON.518993","article-title":"Corneal topography using a smartphone-based corneal topographer considering a biconical model for the corneal surface","volume":"3","year":"2024","journal-title":"Opt. Contin."},{"key":"ref_2","first-page":"26","article-title":"A proposal to eliminate the skew ray error in corneal topography using Placido disks images","volume":"Volume 11102","year":"2019","journal-title":"Proceedings of the Applied Optical Metrology III"},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Vaishnavi, L.L., Bhavana, M., Manideep, D.C.M., and Venugopal, V. (2024, January 26\u201327). A Fast and Accurate Object Counting using Sobel Edge Detection System for Real\u2013Time Star Gazing. Proceedings of the 2024 Asia Pacific Conference on Innovation in Technology (APCIT), Mysore, India.","DOI":"10.1109\/APCIT62007.2024.10673462"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Mogos, G. (2024, January 18\u201320). Quantum Image Processing Using Edge Detection Based on Roberts Cross Operators. 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