/usr/include/dlib/entropy_decoder/ is in libdlib-dev 18.18-2build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/dlib/entropy_decoder/entropy_decoder_kernel_1.h
/usr/include/dlib/entropy_decoder/entropy_decoder_kernel_2.h
/usr/include/dlib/entropy_decoder/entropy_decoder_kernel_abstract.h
/usr/include/dlib/entropy_decoder/entropy_decoder_kernel_c.h
/usr/include/dlib/entropy_decoder_model/entropy_decoder_model_kernel_1.h
/usr/include/dlib/entropy_decoder_model/entropy_decoder_model_kernel_2.h
/usr/include/dlib/entropy_decoder_model/entropy_decoder_model_kernel_3.h
/usr/include/dlib/entropy_decoder_model/entropy_decoder_model_kernel_4.h
/usr/include/dlib/entropy_decoder_model/entropy_decoder_model_kernel_5.h
/usr/include/dlib/entropy_decoder_model/entropy_decoder_model_kernel_6.h
/usr/include/dlib/entropy_decoder_model/entropy_decoder_model_kernel_abstract.h