gimp software package provides GNU Image Manipulation Program, 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 gimp
gimp is installed in your system.
Make ensure the gimp package were installed using the commands given below,
$ sudo dpkg-query -l | grep gimp *
You will get with gimp package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Graphics |
| Package | gimp |
| Version | 2.8.18-1 |
| Description | GNU Image Manipulation Program |
| Sub Section | Graphics |