Can you express the tiles as text or structured data? It's a 220 byte (character) limit. BITBOX node.js library could be a good place to start https://developer.bitcoin.com/bitbox.html
thank you very much! I want to store a small bitmap into 220 byte: 2 byte prefix 26 byte meta data(text descr.) 192 byte pic=16x16 pixel and 6 bit color depth so one can use 64 colors
