dbuenzli / qrc

QR code encoder for OCaml

qrc — QR code encoder for OCaml

%%VERSION%%

Qrc encodes your data into QR codes. It has built-in QR matrix renderers for SVG, ANSI terminal and text.

Qrc is distributed under the ISC license. It has no dependencies.

Homepage: https://erratique.ch/software/qrc

Installation

qrc can be installed with opam:

opam install qrc

If you don't use opam consult the opam file for build instructions.

Documentation

The documentation can be consulted online or via odig doc qrc.

Questions are welcome but better asked on the OCaml forum than on the issue tracker.

Sample programs

The qrtrip tool generates QR codes from the command line. It renders QR matrices to SVG, ANSI terminals and US-ASCII or UTF-8 text.

qrc's Issues

Moving to_svg out of Qrc.Matrix?

(This is more for discussion rather than an actual issue. Let me know if it is not the proper place to discuss.)

It doesn't feel natural to me to have the to_svg function in Qrc.Matrix, which conceptually is just an implementation of a data structure. Other "backends" are in their own module Qrc_fmt. Why no move to_svg there as well, or to a different unit, or just a different sub-module in Qrc? And perhaps make it use a similar interface than other backends (i.e. taking a formatter as argument); or are you concerned by performance of to_svg itself (when running in the browser, I guess)?

SVG backend: l:href not working

I'm trying to directly embed a SVG QR code in an HTML document (more precisely, I inject the code by setting the innerHTML property), and I get a white square. It seems that the <use l:href='#o' ...> reference is not properly understood. Simply dropping the l: prefix solves the issue.

https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/xlink:href claims that xlink:href is deprecated in SVG 2, but Qrc forces the use of version 1 (is it respected by the browser?).

Also, it works fine if I change the l: to xlink: without even defining this prefix! Is there something fishy with the parsing/interpretation of namespaces when parsing (non-X)HTML?

I'm using Chrome 87.0.4280.88.

Anyway, I was also wondering: Is there a strong (performance?/size?) benefit in using a reference instead of inlining the <rect> element for each "on" pixel? I'm concerned by possible clash with other elements with id='o' in the same document.

Have a look at the warnings

@alainfrisch reported to me a few warning he gets when compiling with non-default compiler warnings.

File "private/thirdparty/qrc/qrc.ml", line 290, characters 7-11: 
290 | (**) 
^^^^ 
Error (warning 50): unattached documentation comment (ignored) 

File "private/thirdparty/qrc/qrc.ml", line 301, characters 7-11: 
301 | (**) 
^^^^ 
Error (warning 50): unattached documentation comment (ignored) 

File "private/thirdparty/qrc/qrc.ml", line 312, characters 7-11: 
312 | (**) 
^^^^ 
Error (warning 50): unattached documentation comment (ignored) 

File "private/thirdparty/qrc/qrc.ml", line 31, characters 21-33: 
31 | let create len v = Bytes.create (div_round_up len 8) (if v then 
255 else 0) 
^^^^^^^^^^^^ 
Error (warning 6): label len was omitted in the application of this 
function. 

File "private/thirdparty/qrc/qrc.ml", line 90, characters 2-22: 
90 | type gen = int array (* Generator polynomial coefficients (hi to 
lo). *) 
^^^^^^^^^^^^^^^^^^^^ 
Error (warning 34): unused type gen. 

File "private/thirdparty/qrc/qrc.ml", line 264, characters 22-29: 
264 | let total_bytes (`V version as v) = 
^^^^^^^ 
Error (warning 27): unused variable version. 

File "private/thirdparty/qrc/qrc.ml", line 360, characters 15-18: 
360 | and set_17 i max = 
^^^ 
Error (warning 27): unused variable max. 

File "private/thirdparty/qrc/qrc.ml", line 543, characters 12-13: 
543 | | 1 -> fun ~x ~y -> y mod 2 = 0 
^ 
Error (warning 27): unused variable x. 

File "private/thirdparty/qrc/qrc.ml", line 544, characters 15-16: 
544 | | 2 -> fun ~x ~y -> x mod 3 = 0 
^ 
Error (warning 27): unused variable y. 

File "private/thirdparty/qrc/qrc.ml", line 552, characters 36-44: 
552 | let set_data mask (`V version as v) ec_level data m = (* see 7.7.3 *) 
^^^^^^^^ 
Error (warning 27): unused variable ec_level. 

File "private/thirdparty/qrc/qrc.ml", line 732, characters 20-21: 
732 | let find_mode ?mode s = match mode with Some m -> m | None -> `Byte 
^ 
Error (warning 27): unused variable s.