what would be the minimum screen size to display lightning invoices as a qr-code?
For the Raspberry Pi Zero I found these displays:
- 128x128 pixel LCD display (1.44 inch)
- 200x200 pixel e-paper/e-Ink display (1.54 inch)
- 128x64 pixel OLED display (0.96 inch)
I saw the examples in BOLT#11 and know that it depends on the input type and error correction setting when creating the qr-code.
Would the qr-code be readable if every black dot of the qr-code would be respresented with only one dot? Or do I need for example 4 dots, resulting in a 32x32 qr-code? Would that be enough for lightning invoices? Is it possible to convert the lightning invoice in all uppercase for generating the qr-code in alphanumeric mode which only uses 5.5 bits per character instead of 8?
With the Google Charts API it is possible to generate QR-Codes, this link generates a QR-Code with 128x128 pixel with the first example invoice from BOLT#11 and an error correction of M (allows recovery of up to 15% data loss): https://chart.googleapis.com/chart?cht=qr&chl=lnbc1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdpl2pkx2ctnv5sxxmmwwd5kgetjypeh2ursdae8g6twvus8g6rfwvs8qun0dfjkxaq8rkx3yf5tcsyz3d73gafnh3cax9rn449d9p5uxz9ezhhypd0elx87sjle52x86fux2ypatgddc6k63n7erqz25le42c4u4ecky03ylcqca784w&chs=128x128&chld=M|0