I got really bored so I wrote a simple dithering tool in Kotlin. It is surprising how little loss you get when reducing an image to 8 colors. Source code: https://gist.github.com/Frederikam/115a15450bec82720d3bb5a70b5ceefd
My trip was cancelled. Oh whelp.
Not that I can blame them. They're selling tickets on credit, and my private limited company has next to nothing in registered capital.
Paper tickets are quite rare these days. Most people use a digital code or a universal RFC card.
They probably only sent this by mail because it looks like they tamper-proofed this ticket with microprint.