Design Space of Geometry-based Image Abstraction Techniques with Vectorization Applications Lisa Ihde Hasso Plattner Institute, Digital Engineering Faculty, University of Potsdam, Germany lisa.ihde@student.hpi.uni- potsdam.de Amir Semmo Digital Masterpieces GmbH, Potsdam, Germany amir.semmo@digitalmasterpieces.com Jürgen Döllner Hasso Plattner Institute, Digital Engineering Faculty, University of Potsdam, Germany juergen.doellner@hpi.uni- potsdam.de Matthias Trapp Hasso Plattner Institute, Digital Engineering Faculty, University of Potsdam, Germany matthias.trapp@hpi.uni- potsdam.de Figure 1: Result of vectorized pencil hatching using optimized tonal art maps based on the presented approach. ABSTRACT The paper presents a new approach of optimized vectorization to generate stylized artifacts such as drawings with a plotter or cutouts with a laser cutter. For this, we developed a methodology for transformations between raster and vector space. More over, we identify semiotic aspects of Geometry-based Stylization Techniques (GSTs) and the combination with raster-based stylization techniques. Therefore, the system enables also Fused Stylization Techniques (FSTs). Keywords: Image stylization, Image processing, Vectorization, Non-photorealistic Rendering, Plotting 1 INTRODUCTION 1.1 Motivation Artists use different tools and materials for creative ex- pression, e.g., from traditional techniques such as oil painting or pencil hatching to modern digital fabrica- tion. In recent years, research has focused on imitating these techniques to create computer graphics-based im- ages using Non-photorealistic Rendering (NPR) tech- niques [Kyp13; Dev13]. The resulting images enjoy great popularity and are increasingly used and shared on social media platforms [Sem162]. While the visual quality of these results closely re- sembles the original techniques, they lack certain qual- ities during reproduction, e.g., using canvas printing or similar. However, by using fabrication techniques based on pen plotters — a commodity reproduction hardware that enjoys popularity in the maker culture — pencil hatching or stippling can be easily implemented using a variety of real pencils. The capability and func- Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. tionality of these devices range from professional to hobby level, and are mainly self-built by participant of the maker scene [Mee20]. For the latter, the building instructions are freely available and partially customiz- able, thus not limited to certain spatial sizes or resolu- tions. With respect to this, a pen plotter uses a vectorized image representation to produce a line drawing. Vec- tor graphics add advantages compared to raster im- ages. For example, the resolution of the graphic is then no longer limited and can be scaled up. In addition, connectivity information of graphic primitives facilitate editing processes. Furthermore and due to the geomet- ric representation, vector graphics enable, next to print- ers or plotters, the use of production or fabrication de- vices such as laser cutters [Mue15]. 1.2 Problem Statement Mostly limited by input resolution, for a stylized photo (e.g., transformed using a pencil hatching stylization technique [Sem20]) it would be difficult to trace or reconstruction the individual lines or edges when au- tomatically converted to a vector graphic. This chal- lenge exists due to crossing of lines and used tex- tures to represent the pen pressure (cf. Tonal Art Maps (TAMs) [Pra01]). To obtain an optimized and actu- ally usable vector graphic representation, we need to ISSN 1213-6972 (print) ISSN 1213-6964 (online) Journal of WSCG http://www.wscg.eu Vol.30, No-1-2, 2022 https://www.doi.org/10.24132/JWSCG.2022.12 99