Depending on your package management tool, run the following to install SDL2_image on Linux:
For apt package manager use the following command:
$ sudo apt-get install libsdl2-image-2.0-0-dev
For dnf package manager use the following command:
$ sudo dnf install SDL2_image-devel
For yum package manager use the following command:
$ yum install SDL2_image-devel
And you're good to go!