[Xy-pic] problem with pdf version

[Richard Lewis]

Michael Barr <mbarr at math.mcgill.ca> writes:

> Please consider the following file:
>
> \documentclass{article}
> \usepackage[all]{xy}
> \begin{document}
>
> \let\*\otimes
>  $$\xy
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(50,0)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(40,30)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(30,40)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(0,50)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(-30,40)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(-40,30)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(-50,0)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(40,-30)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(30,-40)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(0,-50)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(-30,-40)*+!!<0ex,1ex>{A\* B}%
> \POS(0,0)*+!!<0ex,1ex>{A\* B}\ar@{->}(-40,-30)*+!!<0ex,1ex>{A\* B}%
>  \endxy$$
>
> \end{document}
>
> Run it through tex and view it with the dvi viewer.  Perfect.  Now run 
> the dvi file through dvipdfm and look at in the Adobe viewer.  Suddenly 
> the A \otimes B in the middle is much darker than all the others.

I see the same using latex->dvips and viewing in gv (all on FreeBSD
should that matter), but if you zoom in close enough the differences
get smaller and smaller---maybe the problem is just rounding errors in
the viewer/converter.  What happens if you print the file?  You could
always use the "invisible" xypic modification on all but one of the
things, or save it as "A(*)B" and use that id as the start of the
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