Question about PNGs in a new shape set

[anthonym overture com]

Hi,

  About a year ago, I created a shape set for drawing BPMN diagrams
(http://www.bpmn.org/).  I used it for a while and have had several
people emailing me asking for it, so I thought I'd submit a patch
to have it included in the core dia.

  The question I have with this is, how do I get my PNGs to look
as nice as those in the other shape sets?   I created the shapes
using dia, then used exporting as a shape to create the PNGs,
however several of the images have white borders and backgrounds.
How do people usually go about cleaning these up?

Thanks,

-Anthony

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Anthony Molinaro                                 <anthonym overture com>