{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T22:27:36Z","timestamp":1783636056054,"version":"3.55.0"},"reference-count":34,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2025,3,4]],"date-time":"2025-03-04T00:00:00Z","timestamp":1741046400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Algorithms"],"abstract":"<jats:p>Nowadays, portrait drawing has become increasingly popular as a means of developing artistic skills and nurturing emotional expression. However, it is challenging for novices to start learning it, as they usually lack a solid grasp of proportions and structural foundations of the five senses. To address this problem, we have studied Portrait Drawing Learning Assistant System (PDLAS) for guiding novices by providing auxiliary lines of facial features, generated by utilizing OpenPose and OpenCV libraries. For PDLAS, we have also presented the exactness assessment method to evaluate drawing accuracy using the Normalized Cross-Correlation (NCC) algorithm. It calculates the similarity score between the drawing result and the initial portrait photo. Unfortunately, the current method does not assess the hair drawing, although it occupies a large part of a portrait and often determines its quality. In this paper, we present a hair drawing evaluation algorithm for the exactness assessment method to offer comprehensive feedback to users in PDLAS. To emphasize hair lines, this algorithm extracts the texture of the hair region by computing the eigenvalues and eigenvectors of the hair image. For evaluations, we applied the proposal to drawing results by seven students from Okayama University, Japan and confirmed the validity. In addition, we observed the NCC score improvement in PDLAS by modifying the face parts with low similarity scores from the exactness assessment method.<\/jats:p>","DOI":"10.3390\/a18030143","type":"journal-article","created":{"date-parts":[[2025,3,4]],"date-time":"2025-03-04T09:01:33Z","timestamp":1741078893000},"page":"143","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["A Hair Drawing Evaluation Algorithm for Exactness Assessment Method in Portrait Drawing Learning Assistant System"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-1931-113X","authenticated-orcid":false,"given":"Yue","family":"Zhang","sequence":"first","affiliation":[{"name":"Department of Information and Communication Systems, Okayama University, Okayama 700-8530, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nobuo","family":"Funabiki","sequence":"additional","affiliation":[{"name":"Department of Information and Communication Systems, Okayama University, Okayama 700-8530, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Erita Cicilia","family":"Febrianti","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, Politeknik Elektronika Negeri Surabaya, Surabaya 60111, Indonesia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0751-7948","authenticated-orcid":false,"given":"Amang","family":"Sudarsono","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, Politeknik Elektronika Negeri Surabaya, Surabaya 60111, Indonesia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3697-8401","authenticated-orcid":false,"given":"Chenchien","family":"Hsu","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, National Taiwan Normal University, Taipei 106308, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,3,4]]},"reference":[{"key":"ref_1","unstructured":"Blake, W., and Lawn, J. (1981). Portrait Drawing, Watson-Guptill Publications Inc."},{"key":"ref_2","unstructured":"Brandt, G.B. (2001). Bridgman\u2019s Complete Guide to Drawing from Life, Sterling Publishing Co., Inc."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Zhang, Y., Kong, Z., Funabiki, N., and Hsu, C.-C. (2024). A study of a drawing exactness assessment method using localized normalized cross-correlations in a portrait drawing learning assistant system. Computers, 13.","DOI":"10.3390\/computers13090215"},{"key":"ref_4","unstructured":"(2025, January 01). CMU Perceptual Computing Lab. Available online: https:\/\/cmu-perceptual-computing-lab.github.io\/openpose\/web\/html\/doc\/index.html."},{"key":"ref_5","unstructured":"(2025, January 01). OpenCV. Available online: https:\/\/opencv.org\/."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Sarvaiya, J., Patnaik, S., and Bombaywala, S. (2009, January 28\u201329). Image Registration by Template Matching Using Normalized Cross-Correlation. Proceedings of the International Conference on Advances in Computing, Control, and Telecommunication Technologies, Bangalore, India.","DOI":"10.1109\/ACT.2009.207"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Huang, Z., Heng, W., Zhou, S., and Inc, M. (November, January 27). Learning to Paint with Model-based Deep Reinforcement Learning. Proceedings of the 2019 IEEE\/CVF International Conference on Computer Vision (ICCV), Seoul, Republic of Korea.","DOI":"10.1109\/ICCV.2019.00880"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"905","DOI":"10.1109\/TPAMI.2022.3147570","article-title":"Quality Metric Guided Portrait Line Drawing Generation from Unpaired Training Data","volume":"45","author":"Yi","year":"2023","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Tong, Z., Chen, X., Ni, B., and Wang, X. (2020). Sketch Generation with Drawing Process Guided by Vector Flow and Grayscale. arXiv.","DOI":"10.1609\/aaai.v35i1.16140"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Looi, L., and Green, R. (2021, January 8\u201310). Estimating Drawing Guidelines for Portrait Drawing. Proceedings of the IVCNZ, Tauranga, New Zealand.","DOI":"10.1109\/IVCNZ54163.2021.9653407"},{"key":"ref_11","unstructured":"Takagi, S., Matsuda, N., Soga, M., Taki, H., Shima, T., and Yoshimoto, F. (2003, January 9\u201311). An educational tool for basic techniques in beginner\u2019s pencil drawing. Proceedings of the PCGI, Tokyo, Japan."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1007\/s41095-021-0227-7","article-title":"DualFace: Two-stage drawing guidance for freehand portrait sketching","volume":"8","author":"Huang","year":"2022","journal-title":"Comput. Vis. Media"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Yi, R., Liu, Y.-J., Lai, Y.-K., and Rosin, P.L. (2019, January 15\u201320). APDrawingGAN: Generating Artistic Portrait Drawings from Face Photos with Hierarchical GANs. Proceedings of the 2019 IEEE\/CVF, Long Beach, CA, USA.","DOI":"10.1109\/CVPR.2019.01100"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Huang, Z., Xie, H., Fukusato, T., and Miyata, K. (2023, January 6\u201310). AniFaceDrawing: Anime Portrait Exploration during Your Sketching. Proceedings of the ACM SIGGRAPH 2023 Conference (SIGGRAPH \u201923), Association for Computing Machinery, New York, NY, USA.","DOI":"10.1145\/3588432.3591548"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Singh, J., Smith, C., Echevarria, J.I., and Zheng, L. (2021). Intelli-Paint: Towards Developing Human-like Painting Agents. arXiv.","DOI":"10.1007\/978-3-031-19787-1_39"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Li, S., Xie, H., Yang, X., Chang, C.-M., and Miyata, K. (2022, January 27\u201329). A Drawing Support System for Sketching Aging Anime Faces. Proceedings of the International Conference on Cyberworlds (CW), Kanazawa, Japan.","DOI":"10.1109\/CW55638.2022.00010"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Kong, Z., Zhang, Y., Funabiki, N., Huo, Y., Kuribayashi, M., and Harahap, D.P. (2023, January 10\u201313). A Proposal of Auxiliary Line Generation Algorithm for Portrait Drawing Learning Assistant System Using OpenPose and OpenCV. Proceedings of the GCCE, Nara, Japan.","DOI":"10.1109\/GCCE59613.2023.10315351"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Henderson, S., and Yeow, J. (2012, January 4\u20137). iPad in Education: A Case Study of iPad Adoption and Use in a Primary School. Proceedings of the 45th Hawaii International Conference on System Sciences, Maui, HI, USA.","DOI":"10.1109\/HICSS.2012.390"},{"key":"ref_19","unstructured":"Fernandez, A.L. (2020). Advances in Teaching Inorganic Chemistry Volume 2: Laboratory Enrichment and Faculty Community, Department of Chemistry and Biochemistry, George Mason University."},{"key":"ref_20","unstructured":"Yongyeon, C. (2022). Tutorials of Visual Graphic Communication Programs for Interior Design 2, Iowa State University Digital Press."},{"key":"ref_21","unstructured":"Hiromasa, U. (2014). Hiromasa\u2019s Drawing Course: How to Draw Faces, Kosaido Pub."},{"key":"ref_22","unstructured":"Gonzalez, R.C., Woods, R.E., and Eddins, S.L. (2020). Digital Image Processing with Matlab, Gatesmark Publishing."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1427","DOI":"10.1109\/TPAMI.2007.70794","article-title":"Robust Real-Time Pattern Matching Using Bayesian Sequential Hypothesis Testing","volume":"30","author":"Pele","year":"2008","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_24","unstructured":"Li, G. (2012, January 16\u201318). Stereo Matching Using Normalized Cross-Correlation in LogRGB Space. Proceedings of the International Conference on Computer Vision in Remote Sensing, Xiamen, China."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Dawoud, N.N., Samir, B., and Janier, J. (2011, January 4\u20136). N-mean Kernel Filter and Normalized Correlation for Face Localization. Proceedings of the IEEE 7th International Colloquium on Signal Processing and Its Applications, Penang, Malaysia.","DOI":"10.1109\/CSPA.2011.5759913"},{"key":"ref_26","first-page":"2249","article-title":"Algorithm for Face Matching Using Normalized Cross-Correlation","volume":"2","author":"Chandran","year":"2013","journal-title":"Int. J. Eng. Adv. Technol."},{"key":"ref_27","unstructured":"Feng, Z., Qingming, H., and Wen, G. (2006, January 14\u201319). Image Matching by Normalized Cross-Correlation. Proceedings of the IEEE International Conference on Acoustics, Speech, and Signal Processing, Toulouse, France."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1109\/TSM.2015.2430453","article-title":"A Region-Based Normalized Cross-Correlation Algorithm for the Vision-Based Positioning of Elongated IC Chips","volume":"28","author":"Zhang","year":"2015","journal-title":"IEEE Trans. Semicond. Manuf."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Hisham, M.B., Yaakob, S.N., Raof, R.A.A., Nazren, A.B.A., and Wafi, N.M. (2015, January 13\u201314). Template Matching Using Sum of Squared Difference and Normalized Cross-Correlation. Proceedings of the IEEE Student Conference on Research and Development, Kuala Lumpur, Malaysia.","DOI":"10.1109\/SCORED.2015.7449303"},{"key":"ref_30","unstructured":"Ban, K.D., Lee, J., Hwang, D.H., and Chung, Y.K. (2008, January 14\u201317). Face Image Registration Methods Using Normalized Cross-Correlation. Proceedings of the International Conference on Control, Automation, and Systems, Seoul, Republic of Korea."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Gao, Q., Chen, H., Yu, R., Yang, J., and Duan, X. (2019, January 13\u201315). A Robot Portraits Pencil Sketching Algorithm Based on Face Component and Texture Segmentation. Proceedings of the IEEE International Conference on Industrial Technology, Melbourne, VIC, Australia.","DOI":"10.1109\/ICIT.2019.8755142"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Zhang, Y., Kong, Z., Funabiki, N., and Hsu, C.-C. (2024, January 14\u201315). An Extension of Drawing Exactness Assessment Method to Hair Evaluation in Portrait Drawing Learning Assistant System. Proceedings of the 2024 8th International Conference on Information Technology (InCIT), Kanazawa, Japan.","DOI":"10.1109\/InCIT63192.2024.10810487"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1016\/j.imavis.2018.02.001","article-title":"Hair Detection, Segmentation, and Hairstyle Classification in the Wild","volume":"71","author":"Muhammad","year":"2018","journal-title":"Image Vis. Comput."},{"key":"ref_34","unstructured":"(2025, January 01). Person Photo. Available online: https:\/\/www.quchao.net\/Generated-Photos.html."}],"container-title":["Algorithms"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4893\/18\/3\/143\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T16:47:03Z","timestamp":1760028423000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4893\/18\/3\/143"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,3,4]]},"references-count":34,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2025,3]]}},"alternative-id":["a18030143"],"URL":"https:\/\/doi.org\/10.3390\/a18030143","relation":{},"ISSN":["1999-4893"],"issn-type":[{"value":"1999-4893","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,3,4]]}}}