$ sudo apt-get install libcurl4-gnutls-dev
$ git clone https://github.com/saitoha/libsixel.git
$ cd libsixel
$ ./configure --with-libcurl
$ sudo make; sudo make install$ sudo ldconfig /usr/local/lib/libsixel.so.1
$ img2sixel sample.png
$ cat sample.png | img2sixel