/usr/share/man/man1/pngtogd2.1.gz is in libgd-tools 2.1.0-5+deb8u11.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man1/libgd-tools.1.gz
/usr/share/man/man1/libgd-tools.1.gz