This is just a little fun project I made, because spending three weekends understanding the QR specification makes far more sense than spending three minutes understanding the GCC flags needed to compile the QR library that I already had. It's certainly a lot more fun, at least.
Everything in this repo is released to the public domain under the Unlicense. While I did take inspiration from various sources across the internet (including the specification itself), I didn't use anybody else's code here, so there's no copyright burden.
Check out the documentation. There's also a little test program that takes command-line arguments and outputs BMP data to standard output.