The jpeg6 library is outdated and no longer maintained, so it is not recommended to install it. Instead, you can install the updated version, libjpeg-turbo, which is a highly optimized JPEG library for Linux.

To install libjpeg-turbo on Ubuntu or Debian-based systems, you can use the apt package manager by running the following command:

sudo apt-get install libjpeg-turbo8-dev  

For CentOS or Fedora-based systems, you can use the yum package manager by running the following command:

sudo yum install libjpeg-turbo-devel  

After installation, you can include the libjpeg-turbo library in your programs and use its functions for JPEG image processing.