A simple method for sending pictures by wire or radio (1936) https://archive.org/details/electronictelevi00eckhrich/page/48/mode/2up
The first image received from Mars: an interplanetary color by numbers (JPL, 1965) http://www.directedplay.com/first-tv-image-of-mars
@th if you use standard Morse code this is not really optimized since you have to use two symbols for the blackest black...
@th This reminds me of the time in Poland (early 90s) where you could get Commodore64 games sent through the radio The c64 used cassettes for storage and some "pirate" stations would play them over the radio so you could tune in and record them onto a cassette on your end.
"Pirate" is in quotes because before 1994 there was no copyright in Poland (thanks to being a post-communist country), so copying/redistributing software was not illegal.