termplay is the tool to convert images to ANSI sequences.
It also supports playing videos.

Features:
* Multiple modes
  * Sixels: Only supported by a few terminals, like xterm.
  * Unicode halfblock: This is the same as TrueColor below, but uses unicode
    half-blocks for smaller pixels.
  * TrueColor: Any RGB color, supported by most terminals.
  * 256 color: The closest representation of a color that can be fit within
    1 byte. Use this if nothing else works.
* Flexible
  * Change framerate, size and more using command line switches.
* Adapting size
  * Automatically scales the image to fit your terminal.