Frequently Asked Questions

Contents

Why are the SVG diagrams dot generates malformed?

UMLGraph uses guillemot characters for representing the angle brackets around stereotypes, as in «interface». By default these are encoded as ISO-8859-1 characters, which are illegal in the UTF-8 output that dot generates for SVG. When using dot to generate SVG output, you should also specify -outputencoding utf8 to UMLGraph.

How can I improve the quality of the bitmap images I generate?

Both dot and pic2plot can directly produce bitmap images in formats like GIF, PNG and PNM. However, if you want to produce presentation-quality output the a vector output format like Postscript or SVG is preferable. If you do require a bitmap format, it might be worth to create it at a higher resolution from a Postscript image, and then downsample it. This procedure (used for the diagrams appearing on the UMLGraph web site) will create an antialiased image of a higher quality than what the default bitmap output options produce. The following pipeline is an example of how you can achieve this effect:
dot -Tps FILENAME.dot |
gs -q -r360 -dNOPAUSE -sDEVICE=pnm -sOutputFile=-  - -c quit |
pnmcrop |
pnmscale 0.25 |
ppmtogif >FILENAME.gif

One other possibility for converting the sequence diagram into Postscript is to pass it through pic and groff. Tools like ps2epsi and ps2eps can then be used to convert the Postscript into encapsulated Postscript. Of course, groff users will just use the pic program as part of their processing pipeline.

A class appears multiple times in a class diagram. Why?

Most probably your class diagram uses packages, and you are not qualifying the classes with the respective package names in the tags you use. The tags are not smart enough to do the package resolution, so you will have to prepend the package name to the class, or avoid using packages.

Problematic Specification

package test;
abstract class AbstractNode {}
/** @composed 1 has * AbstractNode */
class InnerNode extends AbstractNode {}
class Leaf extends AbstractNode {}

First Approach: Class Name Qualified with the Package

package test;
abstract class AbstractNode {}
/** @composed 1 has * test.AbstractNode */
class InnerNode extends AbstractNode {}
class Leaf extends AbstractNode {}

Second Approach: No Package Specification

abstract class AbstractNode {}
/** @composed 1 has * test.AbstractNode */
class InnerNode extends AbstractNode {}
class Leaf extends AbstractNode {}

Shouldn't static fields appear underlined?

Yes they should. Unfortunately, dot does not (yet) support a way to underline single labels, and thus UMLGraph can not show the static fields underlined.

Where can I find a pic2plot executable for Windows?

A port of pic2plot for Windows can be found in GNU PlotUtils, which is part of the GnuWin32 project.

Under Windows the output of pic2plot appears empty. Why?

On Windows platforms note that the current version of pic2plot appears to be very picky about carriage return (CR - \r) characters (by default, CR is part of the platform's end of line sequence) appearing in its input file. Therefore, you will probably want to instruct your editor to create Unix-style files, or filter the files to remove the carriage return characters. The following Perl invocation is such a filter:
perl -p -e "BEGIN {binmode(STDOUT);} s/\r//"
You can remove the CR characters in-place by running:
perl -pi.bak -e "BEGIN {binmode(STDOUT);} s/\r//" FILENAME.pic
In addition, pic2plot appears to require that the last input file be properly terminated (with a newline). Apparently, some Windows editors may leave the last line unterminated, so if your editor is in this category it may be safer to add a blank line in the end.

I have a problem with Maven's Dotuml plugin. Can you help me?

Sorry, I did not develop this plugin, and therefore can not offer help. Have a look at the project's documentation and mailing lists available through plugin web page.