Opensource Library C++ for converting pdf to bitmap? Imagemagick alternative?

I am searching a c++ library which could convert PDF to some bitmap formats.

I found imagemagick and its fork graphicmagick. I tried imagemagick and it fullfill my needs, but the problem is, that it uses ghostscript which is GPL licenced and I could not use a GPL library (unfortunately).

Did anybody know a alternative to this libs without use of ghostscript (via API), so I could avoid GPL problems?

Thank you!