GNU ELPA: qrencode

This package provides three 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.

qrencode-string

Encode a specific string (leading/trailing whitespace trimmed).

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) or vector graphics (SVG) by pressing e in the QR Code buffer. There are also some public elisp library functions to generate QR Codes for use in other elisp code.

Currently two NetPBM formats are supported: P1 and P4. The latter is much smaller and the exporter much faster, so highly recommended. But due to backwards compatibility reasons we currently default to P1. By customizing qrencode-export-format to 'p4 the export format can be changed. In the next major version release P1 support is likely to get dropped in favour of P4.

SVG export is available if svg.el (Emacs 26.1 or newer) is available. This can be selected by customizing qrencode-export-format to 'svg or by using the .svg file name suffix. Filename based format detection is controlled using qrencode-export-format-based-on-filename, which is enabled by default.

(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 GNU ELPA, MELPA, and el-get.

The code is written in pure Emacs Lisp on GNU Emacs 31. 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. 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.