Tuesday, April 18, 2006

Render DOT files on the fly on Mac OS X

Webdot isn't available for Mac OS X, and as I use an iBook running Panther for all my development work (before moving to a Linux box to host the results) I wanted to have the same functionality on my iBook. This can be achieved by hacking a simplified version of webdot. This Perl script creates a virtual web browser to serve the image. I've simplified things somewhat, but it works.

The two things you need to set in the script dot.cgi are the path to your copy of the Graphviz program dot,and a directory where dot can write temporary files (I use /tmp).

You can get a copy of the script here.

To render an image of a graph on the fly you insert an img
tag with the src attribute comprising:

  1. the path to the CGI script, e.g. /cgi-bin/dot.cgi

  2. a '/' delimiter

  3. the URL of the graph file, e.g. http://localhost/~rpage/dot/leda.7.46.gml.dot

  4. the extension of the image format you want (e.g., png, svg, etc.) preceeded by a dot "."

As an example, here is the dot file http://localhost/~rpage/dot/leda.dot as a PNG image, using the HTML:

<img src="/cgi-bin/dot.cgi/http://localhost/~rpage/dot/leda.dot.png" />

The source file for this graph looks like this:

graph G {
node [width=.2,height=.2,fontsize=10];
edge [fontsize=10,len=2];
0 [label="0"];
1 [label="3"];
2 [label="4"];
3 [label="5"];
4 [label="6"];
5 [label="7"];
0 -- 1 [label="13"];
0 -- 2 [label="12"];
0 -- 5 [label="8"];
0 -- 4 [label="71"];
1 -- 5 [label="84"];
1 -- 4 [label="8"];
2 -- 5 [label="18"];
2 -- 4 [label="11"];
2 -- 3 [label="51"];
3 -- 4 [label="87"];

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