I'm running a C++ program using sdl, my ubuntu version is 16.04.
After I sudo apt-get install libsdl1.2-dev and run the following displays :
You only installed SDL library. SDL_image and SDL_ttf are different libraries. You can download them via
sudo apt-get install libsdl-image1.2-dev libsdl-ttf2.0-dev. There is also another popular SDL extension SDL_mixer: