/usr/lib/libGraphicsMagick++.so.3 is in libgraphicsmagick++3 1.3.20-3+deb8u2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/libGraphicsMagick++.so.3.7.0
/usr/lib/libGraphicsMagick++.so.3.7.0