In the 1960s, Eduardo Joselevich and Fanny Fingerman developed a technique to represent images with only four symbols. Full blocks or circles, in either black or white. They called it Fototrama and it was used at Olivetti and Philips for example.
Half-tone style graphics from Argentina. Taken from the book Words & buildings: the art and practice of architectural graphics by Jock Kinneir, 1981.