pdf2ps blackens images

[Lee Howard]

When I convert a PDF with an embedded image (in this case it originated as
transparent-background png, but have also tried white-background) to
Postscript via pdf2ps, the image area is almost completely black.  I'm not
sure if it's just darkening everything in the image area or if it's making
the image area negative, but it's not very pretty.

I'm using ghostscript-5.50 on RedHat 7.0

Has anyone else seen this problem?  Is it a configuration setting or
something I can fix, or what can I do to help diagnose the problem?

Thanks.

Lee Howard