/usr/lib/x86_64-linux-gnu/libloadpng.so is in libloadpng4-dev 2:4.4.2-10.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libloadpng.so.4.4
/usr/lib/x86_64-linux-gnu/libloadpng.so.4.4