Line Labeling

The Java applet below allows you to input an x-monotone polygonal chain. It then generates a strip that contains good candidates for labels placement. The strip baseline will be composed of line and circle segments. For more information about line labeling refer to the article A Simple and Efficient Algorithm for High-Quality Line Labeling (Taylor & Francis, 2000) [html, pdf].

To input a polygonal chain use

• the left mouse button to set the vertices (except for the final vertex),
• the right mouse button to set the final vertex, and
• the middle mouse button (or Shift-left button) to undo the previous vertex.

There are three parameters that you can define using the sliders in the lower part of the applet:

• epsilon defines the minimum distance between the polygonal chain and the strip.
• radius defines the maximum strip curvature. Note that radius must be greater than epsilon.
• height defines the height of the strip.

If you have set everything, use the button Compute Strip to get the initial strip. As soon as the initial strip has been computed, there are more buttons available:

• Refine Strip allows you to refine the strip.
• Clear Strip will do the obvious.
• Min Curve and Min Wiggle will give you a postscript file where the label "Polygonzugbeschriftung" is placed within the current strip. While Min Curve will find a position that minimizes the label curvature, Min Wiggle will find a label position that minimizes the number of strip pieces of different curvature occupied by the label.

If you read this, you do not have a Java-compatible Browser or you have deactivated Java.

Written by Lars Knipping. Ported to Linux using ISO-C++ and addition of proxy support by Johannes Singler.