Ery Arias-Castro, Gilad Lerman, and Teng Zhang. 2017. Spectral Clustering Based on Local PCA. Journal of Machine Learning Research 18 (2017), 1-57.

Anssi Arte. 2015. Forms of Rockin': Graffiti Letters and Popular Culture. Dokument Press.

Jonas August, Kaleem Siddiqi, and Steven W. Zucker. 1999. Ligature Instabilities in the Perceptual Organization of Shape. Computer Vision and Image Understanding 76, 3 (1999), 231-243. https://doi.org/10.1006/cviu.1999.0802

Samaneh Azadi, Matthew Fisher, Vladimir G Kim, Zhaowen Wang, Eli Shechtman, and Trevor Darrell. 2018. Multi-Content GAN for Few-Shot Font Style Transfer. In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition. 7564-7573. https://doi.org/10.1109/CVPR.2018.00789

Alex Bailey. 2001. Class-dependent features and multicategory classification. Ph. D. Dissertation. Southampton Univ. (United Kingdom).

Elena Balashova, Amit H. Bermano, Vladimir G. Kim, Stephen DiVerdi, Aaron Hertz mann, and Thomas Funkhouser. 2019. Learning a Stroke-Based Representation for Fonts. Computer Graphics Forum 38, 1 (2019), 429-442. https://doi.org/10.1111/cgf.

Brad Barber and H Huhdanpaa. 1995. QHull. The Geometry Center, University of Minnesota, http://www. geom. umn. edu/software/qhull (1995).

Alexander Belyaev and Shin Yoshizawa. 2001. On Evolute Cusps and Skeleton Bifurca tions. In International Conference on Shape Modeling and Applications. IEEE, 134-140. https://doi.org/10.1109/SMA.2001.923384

Daniel Berio, Paul Asente, Jose Echevarria, and Frederic Fol Leymarie. 2019. Sketching and Layering Graffiti Primitives. In 8th ACM/Eurographics Expressive Symposium on Computational Aesthetics and Sketch Based Interfaces and Modeling and Non-

Photorealistic Animation and Rendering. 51-59. https://doi.org/10.2312/exp.20191076 Daniel Berio, Sylvain Calinon, and Frederic Fol Leymarie. 2017. Dynamic Graffiti

Stylisation with Stochastic Optimal Control. In Proceedings of the 4th International Conference on Movement Computing. Association for Computing Machinery. https: //doi.org/10.1145/3077981.3078044 Article no. 18.

Daniel Berio, Frederic Fol Leymarie, and Réjean Plamondon. 2018. Expressive Curve Editing with the Sigma Lognormal Model. In Proceedings of the 39th Annual Eu ropean Association for Computer Graphics Conference: Short Papers. Eurographics Association, 33-36.

Daniel Berio, Frederic Fol Leymarie, and Réjean Plamondon. 2020. Kinematics Re construction of Static Calligraphic Traces from Curvilinear Shape Features. In The Lognormality Principle and its Applications in e-Security, e-Learning and e-

Health, Réjean Plamondon, Angelo Marcelli, and Miguel Ángel Ferrer (Eds.). Series in Machine Perception and Artificial Intelligence, Vol. 88. Chapter 11, 237-268. https://doi.org/10.1142/9789811226830_0011

Harry Blum. 1973. Biological Shape and Visual Science (Part I). Journal of Theoretical Biology 38, 2 (1973), 205-287. https://doi.org/10.1016/0022-5193(73)90175-6

Joseph L Brooks. 2015. Traditional and New Principles of Perceptual Grouping. (2015), 57-87.

Neill DF Campbell and Jan Kautz. 2014. Learning a Manifold of Fonts. ACM Transactions

on Graphics (TOG) 33, 4 (2014). https://doi.org/10.1145/2601097.2601212 Article no. 91.

Xudong Chen, Zhouhui Lian, Yingmin Tang, and Jianguo Xiao. 2017. An Automatic

Stroke Extraction Method Using Manifold Learning. In Proceedings of the European Association for Computer Graphics: Short Papers (EG '17). Eurographics Association, 65-68.

Charles H Cox, Philippe Coueignoux, Barry Blesser, and Murray Eden. 1982. Skeletons: A Link Between Theoretical and Physical Letter Descriptions. Pattern Recognition 15, 1 (1982), 11-22. https://doi.org/10.1016/0031-3203(82)90056-5

Rodrigo Pena Carvalho Dos Anjos Craveiro. 2017. The Influence of Graffiti Writing in Contemporary Typography. SAUC — Street Art and Urban Creativity Scientific Journal 3, 2 (2017), 65-83. https://doi.org/10.25765/sauc.v3i2.82

Joeri De Winter and Johan Wagemans. 2006. Segmentation of Object Outlines Into Parts: A Large-Scale Integrative Study. Cognition 99, 3 (2006), 275-325. https: //doi.org/10.1016/j.cognition.2005.03.004

Oliver Deussen, Thomas Lindemeier, Sören Pirk, and Mark Tautzenberger. 2012. Feedback-Guided Stroke Placement for a Painting Machine. In 8th Annual Sympo sium on Computational Aesthetics in Graphics, Visualization, and Imaging. 25-33.

Shay Deutsch and Gérard Medioni. 2017. Learning the Geometric Structure of Manifolds and Vision 57, 3 (2017), 402-422. https://doi.org/10.1007/s10851-016-0684-2

Michel Marie Deza and Elena Deza. 2013. Encyclopedia of Distances. Springer. https: Perception-Based Shape Decomposition. In Computer Vision - ACCV 2012. Lec-

//doi.org/10.1007/978-3-642-30958-8 Updated and revised second edition.

Tim Dwyer, Nathan Hurst, and Damian Merrick. 2008. A Fast and Simple Heuristic for //doi.org/10.1007/978-3-642-37444-9_15 Metro Map Path Simplification. In International Symposium on Visual Computing. Mark Kachanov, Boris Shafiro, and Igor Tsukrov. 2003. Handbook of Elasticity Solutions. Springer, 22-30. https://doi.org/10.1007/978-3-540-89646-3_3 

Udo A. Ernst, Sunita Mandon, Nadja Schinkel-Bielefeld, Simon D. Neitzel, Andreas K. Peter Karow. 1994. Digital Typefaces: Description and Formats. Springer. https: Kreiter, and Klaus R. Pawelzik. 2012. Optimality of Human Contour Integration. //doi.org/10.1007/978-3-642-78105-6 PLOS Computational Biology 8, 5 (2012), 1-17. https://doi.org/10.1371/journal.pcbi. Byungsoo Kim, Oliver Wang, A Cengiz Öztireli, and Markus Gross. 2018. Semantic

Andreas Fabri and Sylvain Pion. 2009. CGAL: The Computational Geometry Algorithms Graphics Forum 37, 2 (2018), 329-338. https://doi.org/10.1111/cgf.13365 Library. In Proceedings of the 17th ACM SIGSPATIAL International Conference on Shaunak Kishore. 2018. Make Me a Hanzi Dataset. https://github.com/skishore/ Advances in Geographic Information Systems (GIS '09). 538--539. https://doi.org/10. makemeahanzi. www.skishore.me/makemeahanzi/ 1145/1653771.1653865 

Alexandre Faure, Lilian Buzer, and Fabien Feschet. 2009. Tangential cover for thick 337-373. https://doi.org/10.1090/S0273-0979-1979-14598-1 digital curves. Pattern Recognition 42, 10 (2009), 2279-2287. https://doi.org/10.1016/ Atsunobu Kotani, Stefanie Tellex, and James Tompkin. 2020. Generating Handwrit j.patcog.2008.11.009 

Jean-Dominique Favreau, Florent Lafarge, and Adrien Bousseau. 2016. Fidelity vs. Simplicity: A Global Approach to Line Drawing Vectorization. ACM Transactions on Graphics (TOG) 35, 4 (2016). https://doi.org/10.1145/2897824.2925946 Article no. Concept Learning Through Probabilistic Program Induction. Science 350, 6266 (2015), 120. 

Vicky Froyen, Jacob Feldman, and Manish Singh. 2015. Bayesian Hierarchical Grouping: Bart Lamiroy, Thomas Bouville, Julien Blégean, Hongliu Cao, Salah Ghamizi, Romain Perceptual Grouping as Mixture Estimation. Psychological Review 122, 4 (2015), Houpin, and Matthias Lloyd. 2015. Re-typograph Phase I: A Proof-of-Concept for 575-597. https://doi.org/10.1037/a0039540 

Hongbo Fu, Shizhe Zhou, Ligang Liu, and Niloy J Mitra. 2011. Animated Construction and Retrieval XXII, Eric K. Ringger and Bart Lamiroy (Eds.), Vol. 9402. International of Line Drawings. In ACM Transactions on Graphics (TOG), Vol. 30. 1-10. https: Society for Optics and Photonics, SPIE, 80-91. //doi.org/10.1145/2070781.2024167 

Mikel Galar, Alberto Fernández, Edurne Barrenechea, Humberto Bustince, and Francisco Mustererkennung 1998. Springer, 85-92. https://doi.org/10.1007/978-3-642-72282-

Herrera. 2011. An overview of ensemble methods for binary classifiers in multi0_7 class problems: Experimental study on one-vs-one and one-vs-all schemes. Pattern R.L. Levien. 2009. From Spiral to Spline: Optimal Techniques in Interactive Curve Design. Recognition 44, 8 (2011), 1761-1776. https://doi.org/10.1016/j.patcog.2011.01.017 Ph. D. Dissertation. EECS Department, University of California, Berkeley. PhD

Étienne Ghys, Sergei Tabachnikov, and Vladlen Timorin. 2013. Osculating Curves: Around the Tait-Kneser Theorem. The Mathematical Intelligencer 35, 1 (2013), 61-66. Michael Leyton. 1987. Symmetry-Curvature Duality. Computer Vision, Graphics, and https://doi.org/10.1007/s00283-012-9336-6 

Peter J. Giblin and Benjamin B. Kimia. 2003. On the Local Form and Transitions of 3 Symmetry Sets, Medial Axes, and Shocks. International Journal of Computer Vision Michael Leyton. 1988. A process-grammar for shape. Artificial Intelligence 34, 2 (March 54, 1 (Aug 2003), 143-157. https://doi.org/10.1109/ICCV.1999.791246

Yotam Gingold, David Salesin, and Denis Zorin. 2008. Stroke-by-Stroke Glyph Animation. Lei Luo, Chunhua Shen, Xinwang Liu, and Chunyuan Zhang. 2015. A Computational Technical Report. Creativity and Graphics Lab (CraGL) at George Mason University, Model of the Short-Cut Rule for 2D Shape Decomposition. IEEE Transactions on Fairfax, Virginia, USA. https://cragl.cs.gmu.edu/fontanim/. 

Andrew Goldberg, Xiaojin Zhu, Aarti Singh, Zhiting Xu, and Robert Nowak. 2009. MultiDiego Macrini, Sven Dickinson, David Fleet, and Kaleem Siddiqi. 2011. Bone Graphs: Manifold Semi-Supervised Learning. In 12th International Conference on Artificial Medial Shape Parsing and Abstraction. Computer Vision and Image Understanding Intelligence and Statistics. 169-176. http://proceedings.mlr.press/v5/goldberg09a. 115, 7 (July 2011), 1044-1061. https://doi.org/10.1016/j.cviu.2010.12.011 html 

David Ha and Douglas Eck. 2018. A Neural Representation of Sketch Draw ings. In Sixth International Conference on Learning Representations (ICLR). https://arxiv.org/abs/1704.03477. 

Tom SF Haines, Oisin Mac Aodha, and Gabriel J Brostow. 2016. My Text in Your Handwriting. ACM Transactions on Graphics (TOG) 35, 3 (2016). https://doi.org/10. https://doi.org/10.1109/ICCV.2007.4409014 1145/2886099 Article no. 26. 

Katherine A Heller and Zoubin Ghahramani. 2005. Bayesian Hierarchical Clustering. out Methods. https://i11www.iti.kit.edu/extra/publications/n-asamm-

In 22nd International Conference on Machine learning (ICML). ACM, 297-304. https: 14.pdf. In 1st Schematic Mapping Workshop. University of Essex, UK. //doi.org/10.1145/1102351.1102389 

Jacky Herz, Roger D Hersch, and Jakob Gonczarowski. 1997. Coherent Processing of Character Skeletal Forms. Computers and Graphics 21, 6 (1997), 727-736. https: the Dutch original of 1985 by Peter Enneson. //doi.org/10.1016/S0097-8493(97)00050-2 

Donald D Hoffman and Whitman A Richards. 1984. Parts of Recognition. Cognition 18, In IEEE Conference on Computer Vision and Pattern Recognition (CVPR). 63-69. https: 1-3 (1984), 65-96. https://doi.org/10.1016/0010-0277(84)90022-2

Donald D Hoffman and Manish Singh. 1997. Salience of Visual Parts. Cognition 63, 1 Nikos Papanelopoulos, Yannis Avrithis, and Stefanos Kollias. 2019. Revisiting the Medial (1997), 29-78. https://doi.org/10.1016/S0010-0277(96)00791-3 

Douglas R Hofstadter. 1982. Variations on a Theme as the Essence of Imagination. Scientific American 247, 4 (1982), 14-21. 

Siu Chi Hsu and Irene H. H. Lee. 1994. Drawing and Animation Using Skeletal Strokes. Curve Detection. IEEE Transactions on Pattern Analysis and Machine Intelligence 11, 21st Annual Conference on Computer Graphics and Interactive Techniques (SIGGRAPH) 8 (1989), 823-839. https://doi.org/10.1109/34.31445 (1994), 109-118. https://doi.org/10.1145/192161.192186 

S. C. Hsu, I. H. H. Lee, and N. E. Wiseman. 1993. Skeletal Strokes. In Proceedings of Rules for Flexible Typeface Synthesis. In Computer Graphics Forum, Vol. 34. 245-256. the 6th Annual ACM Symposium on User Interface Software and Technology (Atlanta, https://doi.org/10.1111/cgf.12763 Georgia, USA) (UIST '93). 197-206. https://doi.org/10.1145/168642.168662

Changyuan Hu and Roger D Hersch. 2001. Parameterizable Fonts Based on Shape Components. IEEE Computer Graphics and Applications 21, 3 (2001), 70-85. https: gence 22, 1 (2000), 63-84. https://doi.org/10.1109/34.824821 //doi.org/10.1109/38.920629 

Elena J. Jakubiak, Ronald N. Perry, and Sarah F. Frisken. 2006. An Improved Rep resentation for Stroke-Based Fonts. In ACM SIGGRAPH 2006 Sketches. https: //doi.org/10.1145/1179849.1180020 

Tingting Jiang, Zhongqian Dong, Chang Ma, and Yizhou Wang. 2013. Toward

ture Notes in Computer Science, Vol. LNCS 7725. Springer, 188-201. https: Springer Netherlands. https://doi.org/10.1007/978-94-017-0169-3 Segmentation for Line Drawing Vectorization Using Neural Networks. Computer

Donald E. Knuth. 1979. Mathematical Typography. Bull. Amer. Math. Soc. 1, 2 (1979), ing via Decoupled Style Descriptors. In Proceedings of the European Conference on

Computer Vision (ECCV). 764-780.

Brenden M Lake, Ruslan Salakhutdinov, and Joshua B Tenenbaum. 2015. Human-Level 1332-1338. https://doi.org/10.1126/science.aab3050 Typeface Parameter Extraction from Historical Documents. In Document Recognition

Longin Jan Latecki and Rolf Lakämper. 1998. Discrete Approach to Curve Evolution. In

thesis, EECS Department, University of California, Berkeley. Image Processing 38, 3 (1987), 327-341. https://doi.org/10.1016/0734-189X(86)90087-

1988), 213-247. https://doi.org/10.1016/0004-3702(88)90039-2 Image Processing 24, 1 (2015), 273-283. https://doi.org/10.1109/TIP.2014.2376188

Diego Macrini, Kaleem Siddiqi, and Sven Dickinson. 2008. From Skeletons To Bone

Graphs: Medial Abstraction for Object Recognition. In IEEE Conference on Computer

Vision and Pattern Recognition (CVPR). https://doi.org/10.1109/CVPR.2008.4587790

Xiaofeng Mi and Doug DeCarlo. 2007. Separating Parts From 2D Shapes Using

Relatability. In IEEE 11th International Conference on Computer Vision (ICCV).

Martin Nöllenburg. 2014. A Survey on Automated Metro Map Lay https://sites.google.com/site/schematicmapping/home.

Gerrit Noordzij. 2005. The Stroke — theory of writing. Hyphen Press. Translated from

Robert L Ogniewicz and Markus Ilg. 1992. Voronoi Skeletons: Theory and Applications. //doi.org/10.1109/CVPR.1992.223226 Axis for Planar Shape Decomposition. Computer Vision and Image Understanding

179 (2019), 66-78. https://doi.org/10.1016/j.cviu.2018.10.007

Pierre Parent and Steven W. Zucker. 1989. Trace Inference, Curvature Consistency, and

Huy Quoc Phan, Hongbo Fu, and Antoni B Chan. 2015. Flexyfont: Learning Transferring

R. Plamondon and S. N. Srihari. 2000. Online and off-line handwriting recognition: a

comprehensive survey. IEEE Transactions on Pattern Analysis and Machine Intelli-

Franco P. Preparata and Michael Ian Shamos. 1985. Intersections. 266-322. https:

//doi.org/10.1007/978-1-4612-1098-6_7

Hock Soon Seah, Zhongke Wu, Feng Tian, Xian Xiao, and Boya Xie. 2005. Artistic Brushstroke Representation and Animation with Disk B-Spline Curve. In ACM SIGCHI International Conference on Advances in Computer Entertainment Technology.

Doron Shaked and Alfred M Bruckstein. 1998. Pruning Medial Axes. Computer Vision and Image Understanding 69, 2 (1998), 156-169. https://doi.org/10.1006/cviu.1997. varying curvature. Such a curve does not have any curvature ex-

Ariel Shamir. 2003. Constraint-Based Approach for Automatic Hinting of Digital Typefaces. ACM Transactions on Graphics (TOG) 22, 2 (2003), 131-151. https: //doi.org/10.1145/636886.636887

Ariel Shamir and Ari Rappoport. 1996. Extraction of Typographic Elements From Outline Representations of Fonts. Computer Graphics Forum 15, 3 (1996), 259-268. circles of a spiral segment with strictly positive or negative curvature https://doi.org/10.1111/1467-8659.1530259 

Kaleem Siddiqi and Benjamin B Kimia. 1995. Parts of Visual Form: Computational Aspects. IEEE Transactions on Pattern Analysis and Machine Intelligence 17, 3 (1995), a sampled curve, looking for additional CSFs for an outline segment 239-251. https://doi.org/10.1109/34.368189 

Manish Singh and Donald D Hoffman. 2001. Part-Based Representations of Visual Shape and Implications for Visual Cognition. In Advances in Psychology. Vol. 130. 401-459. https://doi.org/10.1016/S0166-4115(01)80033-9 

Manish Singh, Gregory D Seyranian, and Donald D Hoffman. 1999. Parsing Silhouettes: two discs as the area of their intersection divided by the area of The Short-Cut Rule. Perception and Psychophysics 61, 4 (1999), 636-660. https: //doi.org/10.3758/BF03205536

Patrick Spröte, Filipp Schmidt, and Roland W Fleming. 2016. Visual Perception of Shape Altered by Inferred Causal History. Scientific Reports 6, 36245 (2016). https: degree of overlap is greater than a user-defined threshold, which //doi.org/10.1038/srep36245

Yuandong Sun, Huihuan Qian, and Yangsheng Xu. 2014. A Geometric Approach to Stroke Extraction for the Chinese Calligraphy Robot. In IEEE International Conference Once we have identified the CSFs for a given outline, we compute on Robotics and Automation (ICRA). 3207-3212. https://doi.org/10.1109/ICRA.2014. a pair of tangents for each concave CSF (§4.2.2). To evaluate the

Rapee Suveeranont and Takeo Igarashi. 2010. Example-Based Automatic Font Genera tion. In Smart Graphics. Number LNCS 6133 in Lecture Notes in Computer Science. from which we keep the first tangents next to the ends of the contact 127-138. https://doi.org/10.1007/978-3-642-13544-6_12

Fan Tang, Weiming Dong, Yiping Meng, Xing Mei, Feiyue Huang, Xiaopeng Zhang, and Oliver Deussen. 2017. Animated Construction of Chinese Brush Paintings. IEEE Transactions on Visualization and Computer Graphics 24, 12 (2017), 3019-3031. et al. 2009] could also be used. https://doi.org/10.1109/TVCG.2017.2774292

S P Timoshenko and J N Goodier. 1951. Theory of Elasticity. McGraw-Hill. https: //books.google.co.uk/books?id=11ISAAAAIAAJ 

Johan Wagemans. 2018. Perceptual Organization. In Stevens' Handbook of Experimental Psychology and Cognitive Neuroscience, Sensation, Perception, and Attention. Vol. 2. Our association fields are adapted from Ernst et al. [2012]. The model Chapter 18, 803-872. https://doi.org/10.1002/9781119170174.epcn218 4th Edition. predicts the conditional link probability of one oriented element

Johan Wagemans, Andrea J van Doorn, and Jan J Koenderink. 2011. Measuring 3D Point Configurations in Pictorial Space. i-Perception 2, 1 (2011), 77-111. https: //doi.org/10.1068/i0420 

Jue Wang, Chenyu Wu, Ying-Qing Xu, Heung-Yeung Shum, and Liang Ji. 2002. Learningparameterizes deviations from perfect cocircularity and deviations Based Cursive Handwriting Synthesis. In Eighth IEEE International Workshop on Frontiers in Handwriting Recognition. 157-162. https://doi.org/10.1109/IWFHR.2002.

Yue Wang. 2013. Interview with Charles Bigelow. TUGboat 34, 2 (2013), 136-167.

Carl-Fredrik Westin, Stephan E Maier, Hatsuho Mamata, Arya Nabavi, Ferenc A Jolesz, and Ron Kikinis. 2002. Processing and Visualization for Diffusion Tensor MRI. Medical Image Analysis 6, 2 (2002), 93-108. https://doi.org/10.1016/S1361-8415(02) 00053-1 

Lance Williams and Karvel K Thornber. 2001. Orientation, Scale, and Discontinuity 𝐴𝜙 = cosh 2 cos (𝛽/2) + 2 cos (𝜃 − 𝛽/2) , (15) as Emergent Properties of Illusory Contour Shape. Neural Computation 13, 8 (Aug 4 𝜎𝛽 𝜎𝜃 2001), 1683-1711. https://doi.org/10.1162/08997660152469305

Songhua Xu, Hao Jiang, Francis CM Lau, and Yunhe Pan. 2012. Computationally Evaluating and Reproducing the Beauty of Chinese Calligraphy. IEEE Intelligent Systems 3 (2012), 63-72. https://doi.org/10.1109/MIS.2012.46 

Yaoda Xu and Manish Singh. 2002. Early Computation of Part Structure: Evidence From Visual Search. Perception and Psychophysics 64, 7 (2002), 1039-1054. https: //doi.org/10.3758/BF03194755

Shih Cheng Yen and Leif H. Finkel. 1998. Extraction of Perceptually Salient Contours by Striate Cortical Networks. Vision Research 38, 5 (1998), 719-741. https://doi.org/ 10.1016/S0042-6989(97)00197-1

Junsong Zhang, Yu Wang, Weiyi Xiao, and Zhenshan Luo. 2017. Synthesizing Or namental Typefaces. Computer Graphics Forum 36, 1 (2017), 64-75. https: //doi.org/10.1111/cgf.12785

Zhiyuan Zhao and Alan Saalfeld. 1997. Linear-time sleeve-fitting polyline sim plification algorithms. In Proceedings of the 13th AutoCarto symposium, Vol. 13. https://cartogis.org, 214-223.

Changqing Zou, Junjie Cao, Warunika Ranaweera, Ibraheem Alhashim, Ping Tan, Alla Sheffer, and Hao Zhang. 2016. Legible Compact Calligrams. ACM Transactions on Graphics (TOG) 35, 4, Article 122 (2016), 12 pages. https://doi.org/10.1145/2897824. between the contact regions of the two CSFs is a spiral. However its local 2925887 Article no. 122. 

A CSF COMPUTATIONS 

When searching for additional CSFs (§4.2.1), we need to avoid false

approximate spirals. A spiral is a curve segment with monotonically trema between its ends [Leyton 1987] and thus should not produce an additional CSF. This can be further characterized by the Tait-

Kneser theorem [Ghys et al. 2013], which states that all osculating

are disjoint and nested. However, because CSF analysis operates on

that closely resembles a spiral is likely to produce many additional