Continuous Line Drawings and Designs

Continuous Line Drawing (CLD) is a drawing style where a picture consists of a single closed non-intersecting line. This paper presents an automatic algorithm for constructing CLDs, with tone and structural information obtained from input images. The connectivity of the line is maintained through a tree generated by path finding with consideration of the key features for a given image. A branching tree structure is grown incrementally by selecting pixels by a cost function, relating to both the tone map and an importance map. After labeling each branch, an artificial wall is then constructed through a two-stage labeling propagation process to produce a single boundary, interpreted as the final CLD. The presented CLD method is effective and automatic, and provides some opportunities for variations. The paper also shows how to design CLDs from scratch using three steps: building base structures, forming shapes by thickening, and extracting CLDs by tracing the boundary of the shapes.