QR code in ConTeXt

Question

In LaTeX there is a the qrcode package. Is there any way to create a qrcode in ConTeXt?

Something like this:

\qr[1in]{Your text to be QR encoded here}

Answer 1

A first attempt. We can generate a MetaPost graphic if we want, but this seems faster and easier to do. With some more commands, we can even write a small module, in case anyone else needs it. You only need qrencode.lua from here (the other files are prescindible).

EDIT: My first solution only worked with ConTeXt LMTX. The following one should work both with MkIV and LMTX. At this point it's better to moving to the latter, though.

\startluacode

local table      = table 
local concat     = table.concat

local interfaces = interfaces
local implement  = interfaces.implement

local qr = require"qrencode"

local function helper(n)
    if n > 0  then return 0      end
    if n < 0  then return 2^24-1 end
    if n == 0 then return 2^12   end --Should it happen?
end

local function qrcode_to_ctx(size, text)
    local n, data, settings
    local ok, content = qr.qrcode(text)
    local result = ''

    if not ok then
        context.type(content) 
    else
        data     = {}
        n        = #content
        settings = {
            x      = n, 
            y      = n,
            width  = size,
            height = size
        }    
        for i = 1, n do
            data[i] = {}
            for j = 1, n do
                data[i][j] = ('%06X'):format(helper(content[i][j]))
            end
            result = result .. concat(data[i])
        end
        context.bitmapimage(settings,result)
    end
end

implement{
    name      = 'qrcode',
    arguments = {'string', 'string'},
    actions   = qrcode_to_ctx
}

\stopluacode
\unprotect
\unexpanded\def\qrcode{\dosingleempty\qrcode_direct}
\def\qrcode_direct[#1]#2%
    {\quitvmode\doifsomethingelse{#1}%
     {\clf_qrcode{#1}{#2}}
     {\clf_qrcode{1cm}{#2}}} %Change 1cm for another default
\protect
\starttext
\startTEXpage
\qrcode[5cm]{https://tex.stackexchange.com/questions/598634/qr-code-in-context}
\stopTEXpage
\stoptext