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Bacon / BaconQrCode

QR Code Generator for PHP
BSD 2-Clause "Simplified" License
1.83k stars 208 forks source link

Excessive version selected, mode optimisation support? #111

Open Synchro opened 2 years ago

Synchro commented 2 years ago

I'm generating a QR from a URL that has 48 ASCII chars and using Q redundancy, which should mean the total data size is 60 bytes. For that amount of data, this library generates a 37x37 version 5 QR. Looking at this chart, I can see that the capacity of a version 5 does correspond to 60 bytes in "binary" mode, but version 4 can accommodate 67 bytes in "alphanumeric" mode. This chart shows that that this set includes :, ., and / which is all that's needed for URL support, but it does not support lower-case chars. So now I'm mystified because I have a QR generated by a different system that is a version 4 and successfully encodes my URL containing lower-case chars with the correct degree of redundancy.

I suspect that this is due to the other system supporting mode optimisation, where the data can be split into chunks, each with a different encoding mode, for example if my URL contains https://www.example.com/ABC1234567890/XYZ, this could be encoded as a byte-mode chunk of https://www.example.com followed by an alphanumeric chunk of /ABC1234567890/XYZ, or possibly even finer chunks if 1234567890 could be dropped to numeric mode.

This page has an excellent demonstration of mode optimization along with a detailed description of how it works.

Do you have any plans to implement this optimisation so we can have smaller QRs?

DASPRiD commented 6 months ago

I don't personally plan to make any future enhancements, but I'm open to accept PRs.