gvcolor - flow colors through a ranked digraph

       Stephen C. North <north@research.att.com>
       Emden R. Gansner <erg@research.att.com>

       It would be nice to make the program work without relying on an initial pass through dot.

gvcolor  (previously  known  as  colorize)  is  a  filter that sets node colors from initial seed values.
       Colors flow along edges from tail to head, and are averaged (as HSB vectors) at nodes.   Thegraphmustalreadyhavebeenprocessedbydot.  Appropriate choice of initial colors yields drawings in which node
       colors help to emphasize logical relationships between nodes, even when they are spread far apart in  the
       layout.

       Initial  colors  must  be  set externally, using the color attribute of a node.  It is often effective to
       assign colors to a few key source or sink nodes, manually setting their colors by editing the graph file.
       Color names are as in dot(1): symbolic names  or  RGB  triples.   It  is  best  to  choose  some  easily‐
       distinguished  but  related  colors;  not necessarily spaced evenly around the color wheel.  For example,
       blue_green, green, and light_yellow looks better than red, green, blue.

       Certain graph attributes control the gvcolor algorithm.  flow=back reverses the flow of colors from heads
       to tails.  saturation=.1,.9 (or any two numbers between 0 and 1) adjusts the  color  saturation  linearly
       from  least  to greatest rank.  If Defcolor is set, this color value is applied to any node not otherwise
       colored.

       The following exit values are returned:

       0   Successful completion.

       1   If nodes of the graph do not possess a ``pos'' attribute.

       gvcolor - flow colors through a ranked digraph

gc(1), dot(1), gvpr(1), ccomps(1), sccmap(1), tred(1), libgraph(3)

                                                  21 March 2001                                       GVCOLOR(1)

gvcolor [ files ]

       dot file.gv | gvcolor | dot -T<format>