/usr/lib/x86_64-linux-gnu/libvips.so.15 is in libvips15 7.28.5-1+deb7u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libvips.so.15.16.5
/usr/lib/x86_64-linux-gnu/libvips.so.15.16.5