Flexible Vectorization and Colorization Tools for Line Drawings


Student thesis: Master's Thesis

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Awarding Institution
  • Hongbo FU (Supervisor)
  • Zhi-Qiang LIU (Supervisor)
Award date26 Sep 2017


Vector art is one of the most common forms of two-dimensional computer graphics. Design of vector grahics is prevalent across a wide range of applications and domains. In common commercial softwares, such as Adobe Illustrator, CorelDraw, and Inkscape,the workflow for designing vector graphics mainly has two steps: first generate sketches by digitally drawing curves one by one or tracing existing line drawing images, and then fill the canvas by colours or textures to generate visually more pleasing vector arts. In this work, we provid novel tools to facilite such a design workflow, including a vectorization tool for extracting curves from complex line drawings, and a coloring tool for creating smooth shading vector graphics.

First, we propose a novel vectorization algorithm for line drawings with arbitrary and complex shapes. We develop a tracing-based approach, based on the key observation that the lines in many drawings are of near-constant width. The key is to derive correct tracing directions, which are determined based on an automatically estimated orientation field, shape smoothness and the near-constant line width assumption.

Second, we provide a novel interactive tool for creating complex color gradients based on diffusion curves. Our technique automatically computes the colors and positons of control points based on user input scribbles. We detect curve segments that are influenced by input scribbles, and then transfer color curve segments to color points. To detect the relationship of curve segments and input scribbles, we solve a combination optimization problem for a single scribble and solve a partition problem for multiple scribbles.

We have examined our algorithms on a variety of line drawings with different shape and topology complexity. We shows that our technique provides significant improvements in efficiency and flexibility for creating vector graphics.