A graph-based method for fitting planar B-spline curves with intersections

Bo, Pengbo; Luo, Gongning; Wang, Kuanquan

doi:10.1016/j.jcde.2015.05.001

Cited by 22 publications

(17 citation statements)

References 22 publications

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“…Limitations. Similarly to most methods of this category [Bo et al 2016;Favreau et al 2016;Noris et al 2013], our method works best on drawings without shading ( Fig. 24(a,b), the nose of the cat in Fig.…”

Section: Hippo Penguinmentioning

confidence: 59%

“…Vectorization of bitmapped images has been studied extensively in graphics, vision, and other disciplines. Various input-and application-speci c priors guide many vectorization methods, conforming to requirements of end users in medical imaging, road map reconstruction from GPS traces, processing of (a) A tangent field at a junction by Chen et al [2015] (b) Our frame field on a similar input astronomical imagery, and other tasks [Bo et al 2016;Chai et al 2013;Türetken et al 2013]. ese methods are application-speci c and cannot be applied directly to vectorization of hand-drawn line drawings.…”

Section: Related Workmentioning

confidence: 99%

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Vectorization of Line Drawings via Polyvector Fields

2019

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Input imageFrame eld Final result Fig. 1. Given a possibly noisy grayscale bitmap image, we compute a frame field aligned with the directions on the image, superimposing multiple directions around sharp corners as well as X-and T-junctions. We then use this frame field to extract the drawing topology and create the final vectorization with the computed topology. Frame field computation (shown for a subset of pixels in the upper zoom and the full field in the lower one) is the key component of the system. The frame field disambiguates X-and T-junctions even in the noisy areas, allowing tracing to be straightforward and robust. Input images are from www.easy-drawings-and-sketches.com, ©Ivan Huska.Image tracing is a foundational component of the work ow in graphic design, engineering, and computer animation, linking hand-drawn concept images to collections of smooth curves needed for geometry processing and editing. Even for clean line drawings, modern algorithms o en fail to faithfully vectorize junctions, or points at which curves meet; this produces vector drawings with incorrect connectivity. is subtle issue undermines the practical application of vectorization tools and accounts for hesitance among artists and engineers to use automatic vectorization so ware. To address this issue, we propose a novel image vectorization method based on state-of-the-art mathematical algorithms for frame eld processing. Our algorithm is tailored speci cally to disambiguate junctions without sacri cing quality.

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Section: Hippo Penguinmentioning

confidence: 59%

Section: Related Workmentioning

confidence: 99%

Vectorization of Line Drawings via Polyvector Fields

2019

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“…Hence, modifying the appearance of strokes first requires extracting approximate curves from the buffer. One solution is to fit parametric curves to the edge image using vectorization algorithms (e.g., (Favreau et al, 2016;Bo et al, 2016)), but this tends to introduce inaccuracies and is often too slow for real-time applications.…”

Section: Discussion and Extensionsmentioning

confidence: 99%

Line Drawings from 3D Models: A Tutorial

Bénard¹,

Hertzmann²

2019

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This tutorial describes the geometry and algorithms for generating line drawings from 3D models, focusing on occluding contours.The geometry of occluding contours on meshes and on smooth surfaces is described in detail, together with algorithms for extracting contours, computing their visibility, and creating stylized renderings and animations. Exact methods and hardware-accelerated fast methods are both described, and the trade-offs between different methods are discussed. The tutorial brings together and organizes material that, at present, is scattered throughout the literature. It also includes some novel explanations, and implementation tips.We believe that these topics ought to be known by anyone interested in understanding the curves in visual representational art. It is one where computer graphics can make a unique contribution. Arguably, the algorithmic simulation of line drawing is a crucial step in understanding visual art. Occluding contoursThis tutorial focuses on the curves known as occluding contours or, simply contours. In some computer graphics research, these have been called silhouettes, though the silhouettes are technically a separate set of curves, as we will describe below.The occluding contours of a simple 3D object are shown in Figure 1.1. As a first definition, suppose we have a 3D object that we wish to render from a specific viewpoint. The occluding contours are surface curves that separate visible parts from invisible parts. By rendering the visible portions of these 3D curves together with the object, we get a basic line drawing (Figure 1.1b).There are many different contour detection and rendering algorithms, and some significant tradeoffs between them. The most important tradeoff is between simple algorithms that produce approximate results, and more complex algorithms that give more precision, control, and stylization capabilities. Just rendering reasonable-looking contours as solid black lines is very straightforward for a graphics programmer. These most basic algorithms can be implemented in a few additional lines of code in an existing renderer, and have been implemented in many real-time applications, including many popular video games (one of the earliest was Jet Set Radio in 2000). However, if we wish to stylize the curves, for example, by rendering the curves with sketchy or calligraphic strokes (Figure 1.1d), things become more difficult. With a bit of perseverance, renderings with distinctive and lovely styles can be created. At times, these renderings may still contain topological artifacts that are not suitable for very high-end production. High-quality algorithms that remove these artifacts are more complex; in the extreme, no provably-correct algorithm exists for this problem. However, there are a number of partial solutions that are good enough to be used in many circumstances, and we discuss in detail the issues involved.Note that, formally, the occluding contour and occluding contour generator are separate curves in 2D and 3D. However, we will frequently use the te...

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“…In order to recognize that two crossing paths actually belong to the same "conceptual" path, a strong semantic knowledge of the underlying structures is necessary, but this is beyond the scope of this paper. A treatment of the problem can be found in [Bo et al 2016], where they correctly group consecutive intersecting line segments.…”

Section: Path Classificationmentioning

confidence: 99%

A complete hand-drawn sketch vectorization framework

Donati

Cesano

Prati

2019

Multimed Tools Appl

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Vectorizing hand-drawn sketches is a challenging task, which is of paramount importance for creating CAD vectorized versions for the fashion and creative workflows. This paper proposes a complete framework that automatically transforms noisy and complex hand-drawn sketches with different stroke types in a precise, reliable and highly-simplified vectorized model.The proposed framework includes a novel line extraction algorithm based on a multi-resolution application of Pearson's cross correlation and a new unbiased thinning algorithm that can get rid of scribbles and variable-width strokes to obtain clean 1-pixel lines. Other contributions include variants of pruning, merging and edge linking procedures to post-process the obtained paths. Finally, a modification of the original Schneider's vectorization algorithm is designed to obtain fewer control points in the resulting Bezier splines.All the proposed steps of the framework have been extensively tested and compared with state-of-the-art algorithms, showing (both qualitatively and quantitatively) its outperformance.

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A graph-based method for fitting planar B-spline curves with intersections

Cited by 22 publications

References 22 publications

Vectorization of Line Drawings via Polyvector Fields

Vectorization of Line Drawings via Polyvector Fields

Line Drawings from 3D Models: A Tutorial

A complete hand-drawn sketch vectorization framework

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