graphvizmargins

Reducing excessive Graphviz octagon margins

The Graphviz output of octagon-shaped nodes has huge margins, even we set "margin=0.0,0.0".

Example:

digraph G {
  foo [shape=octagon, label="one\ntwo", margin="0.0,0.0"];
}

Produces:

digraph G

I want to have smaller margins than those, with the letter edges close to the diagonal edges of octagon. Can I do that?

Solution

  • simple answer: not easily. you are encountering two issues:

    more complex: here is an improvement, but it is a (repeatable) kludge. It does graph layout & octagon sizing using a small font, then resets the fontsize to correct (desired) value. It uses gvpr (http://www.graphviz.org/pdf/gvpr.1.pdf) and neato -n2 (http://www.graphviz.org/faq/#FaqDotWithCoords)

    1. give all your octagon nodes an explicit fontsize that is 3 points smaller that you actually want. Since default fontsize is 14 (https://graphviz.org/docs/attrs/fontsize/), try [fontsize=11]
    2. run this pipeline to layout your graph, and then reset the fontsize:
    dot myfile.gv |
gvpr -c 'N[shape=="octagon"]{$.fixedsize="true"; $.fontsize=$.fontsize + 3;}' | neato -n2 -Tpng >myfile.png

    A modified version of "one two" (with reduced height & width):

    digraph G {
  foo [fontsize=11 height=.4 width=.6 fixedsize=true shape=octagon label="one\ntwo"]
}

    Gives:
    enter image description here

    And a larger input file:

    graph Y{
rankdir=LR
label="simple octagon"
aeiou
onemore [shape=rect]
node[fontsize=11]
foo1 [shape=octagon, label="ab\na"]
foo3 [shape=octagon, label="abcd\nabc"]
foo5 [shape=octagon, label="abcdef\nabcde"]
foo7 [shape=octagon, label="abcdefgh\nabcdefg"]
foo9 [shape=octagon, label="abcdefghij\nabcdefghi"]
foo11 [shape=octagon, label="abcdefghijkl\nabcdefghijk"]
foo13 [shape=octagon, label="abcdefghijklmn\nabcdefghijklm"]
foo15 [shape=octagon, label="abcdefghijklmnop\nabcdefghijklmno"]
foo17 [shape=octagon, label="abcdefghijklmnopqr\nabcdefghijklmnopq"]
foo19 [shape=octagon, label="abcdefghijklmnopqrst\nabcdefghijklmnopqrs"]
}

    Gives:
    enter image description here