QR Code encoder written in pure Emacs Lisp.
For example the self-link (https://github.com/ruediger/qrencode-el) below was generated using this code:
This package provides two user facing interactive functions, that will encode text into a QR Code and show it in a separate buffer.
qrencode-region- Shows the current selection as a QR Code.
qrencode-url-at-point- Encode URL at point as QR Code.
Some customizations are provided using M-x customize-group RET
qrencode RET.
QR Codes are rendered as Unicode text, but there is an option to export them as bitmap (NetPBM format). There are also some public elisp library functions to generate QR Codes for use in other elisp code.
This package only supports exporting to NetPBM format due to the
simplicity of the format. If PNG or other bitmap formats are
desired this can be achieved by using
qrencode-post-export-functions to run a conversion after the
export. For example using convert(1) from ImageMagick:
(add-hook 'qrencode-post-export-functions
#'(lambda (filename)
(call-process "convert" nil nil nil
filename
(file-name-with-extension filename "png"))))
QREncode is available via MELPA and el-get.
The code is written in pure Emacs Lisp on GNU Emacs 27. It should
be backwards compatible to GNU Emacs 25.1 and potentially even
earlier with seq and cl-lib compat libraries.
There are unit tests and an integration test using zbar.sf.net
(Debian/Ubuntu package zbar-tools) to verify that generated QR
Codes can be decoded. Unfortunately zbar doesn’t handle UTF-8 well,
which prevents automated testing of Unicode.
https://qrlogo.kaarposoft.dk/qrdecode.html is another good way to
test the generated codes, since the decoder supports debug output.
The encoder is written for the ISO/IEC 18004:2015 standard. It only supports regular QR Codes (Model 2) and byte encoding (#11). I believe this is sufficient for use-cases in GNU Emacs. The word “QR Code” is registered trademark of DENSO WAVE INCORPORATED in Japan and other countries.