Single-Line Drawing Vectorization

publication
Pacific Graphics 2025
authors
Tanguy Magne, Olga Sorkine-Hornung

Left and middle: A raster single-line drawing and the parameterized vectorization computed with our method. The insets show the vectorization overlaying on top of the raster image. The color gradient encodes the parameterization of the curve, showing the plausible drawing order produced by our method. Right: Since our vectorization is correctly parameterized and composed of one curve, it easily enables applications such as machine embroidery, where the stitches are sequentially sewn along the curve.

abstract

Vectorizing line drawings is a repetitive, yet necessary task that professional creatives must perform to obtain an easily editable and scalable digital representation of a raster sketch. State-of-the-art automatic methods in this domain can create series of curves that closely fit the appearance of the drawing. However, they often neglect the line parameterization. Thus, their vector representation cannot be edited naturally by following the drawing order. We present a novel method for single-line drawing vectorization that addresses this issue. Single-line drawings consist of a single stroke, where the line can intersect itself multiple times, making the drawing order non-trivial to recover. Our method fits a single parametric curve, represented as a Bézier spline, to approximate the stroke in the input raster image. To this end, we produce a graph representation of the input and employ geometric priors and a specially trained neural network to correctly capture and classify curve intersections and their traversal configuration. Our method is easily extended to drawings containing multiple strokes while preserving their integrity and order. We compare our vectorized results with the work of several artists, showing that our stroke order is similar to the one artists employ naturally. Our vectorization method achieves state-of-the-art results in terms of similarity with the original drawing and quality of the vectorization on a benchmark of single-line drawings. Our method's results can be refined interactively, making it easy to integrate into professional workflows.

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acknowledgments

We thank the anonymous reviewers for their detailed feedback and helpful suggestions. We express our gratitude to Marcel Padilla and Loïc Magne for their insightful comments and to Danielle Luterbacher for her help with the embroidery process. Open access publishing facilitated by Eidgenossische Technische Hochschule Zurich, as part of the Wiley - Eidgenossische Technische Hochschule Zurich agreement via the Consortium Of Swiss Academic Libraries.