SVG to PNG transcoding and phaysical image sizes

Hi,

in one of our projects, we are currently using the PNGTranscoder to 
produce a PNG from an SVG, and everything works just fine (in terms of 
expected output, content, ...). As part of some recent testing, we came 
to realize that the PNGs produced are of differing physical byte sizes 
on different machines.

E.g. a PNG image of dimension 1620x1118 px one one box has a size of 
10,836 bytes, whereas a second server produces 10,864 bytes worth of PNG 
from the very same SVG (using the very same binary and thus process). Is 
this something we should be expecting, and if so, why is this the case ?

Just some more contextual information:

- We tried this with Java 6u27, 6u31 and 6u323, and it looks like 
switching between Java version on any given host does not make any 
difference.
- The servers in question run a variety of OS, incl. Windows 8, Linux 
Mint, Linux Ubuntu.

Any idea what might cause these effects ?

Kind regards
Werner Guttmann