plotting

To visualise the R-trees created by the library, one can use the rtree-eps program which creates PostScript plots. Typically one would convert these files to PDF for inclusion in documents or (as here) to a raster format like PNG using ImageMagick or similar software.

The rtree-eps program allows one to style the resulting plot, adjusting the colour of the rectangle fill and the width and colour of lines, using a custom style file. It is easy enough to create your own files (they are just JSON), but several are included in the distribution and previews of these are shown below.

two-level styles

An R-tree with two levels will typically have fewer than a hundred rectangles, barely worth the effort of using the library, but such are useful for testing and development. The jjg2 style is used on the project homepage.

three-level styles

The three-level styles are for small but realistic R-trees with up to a few thousand rectangles. For the most part these use the sequential colour-schemas by Cynthia Brewer (hence prefixed cb-). For further details, see the ColorBrewer2 site or Brewer's page on cpt-city.