contextfree software package provides image generator based on context-free grammars, you can install in your Debian 8 (Jessie) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install contextfree
contextfree is installed in your system.
Make ensure the contextfree package were installed using the commands given below,
$ sudo dpkg-query -l | grep contextfree *
You will get with contextfree package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Graphics |
| Package | contextfree |
| Version | 3.0.5+dfsg1-2.2+b1 [s390x], 3. |
| Description | image generator based on context-free grammars |
| Sub Section | Graphics |