APRIL 18-21, 2017
Radial Contour Labeling with Straight Leaders
The usefulness of technical drawings as well as scientific illustrations \ such as medical drawings of human anatomy essentially depends on \ the placement of labels that describe all relevant parts of the figure. \ In order to not spoil or clutter the figure with text, the labels are \ often placed around the figure and are associated by thin connecting \ lines to their features, respectively. This labeling technique is known \ as external label placement. \ In this paper we introduce a flexible and general approach for \ external label placement assuming a contour of the figure prescribing \ the possible positions of the labels. While much research on \ external label placement aims for fast labeling procedures for interactive \ systems, we focus on highest-quality illustrations. Based on \ interviews with domain experts and a semi-automatic analysis of \ 202 handmade anatomical drawings, we identify a set of 18 layout \ quality criteria, naturally not all of equal importance. We design a \ new geometric label placement algorithm that is based only on the \ most important criteria. Yet, other criteria can flexibly be included in \ the algorithm, either as hard constraints not to be violated or as soft \ constraints whose violation is penalized by a general cost function. \ We formally prove that our approach yields labelings that satisfy all \ hard constraints and have minimum overall cost. Introducing several \ speedup techniques, we further demonstrate how to deploy our \ approach in practice. In an experimental evaluation on real-world \ anatomical drawings we show that the resulting labelings are of high \ quality and can be produced in adequate time.