aa3d software package provides ASCII art stereogram generator, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install aa3d
aa3d is installed in your system.
Make ensure the aa3d package were installed using the commands given below,
$ sudo dpkg-query -l | grep aa3d *
You will get with aa3d package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Graphics |
| Package | aa3d |
| Version | 1.0-8+b1 [armhf], 1.0-8 [amd64 |
| Description | ASCII art stereogram generator |
| Sub Section | Graphics |