.TH QR 1
.SH NAME
qr \- generate QR code
.SH SYNOPSIS
.B qr
[
.B -LMQHna
]
[
.B -v
.I version
]
.SH DESCRIPTION
.I Qr
generates a QR code from the data it reads on standard input.
The QR code is generated as an
.IR image (6)
on standard output.
.PP
The
.B -LMQH
options set the level of error correction.
.B -L
is the lowest and
.B -H
is the highest level.
The default is
.BR -M .
.PP
The QR standard defines different sizes labelled version 1 to version 40.
By default the smallest possible is chosen automatically.
The
.B -v
option forces the use of a particular version.
.PP
By default bytes are encoded directly with no translation.
Coding efficiency can be increased by reducing the set of legitimate characters using the 
.B -an
options.
The 
.B -n
option supports only numbers and the
.B -a
option supports letters, numbers, spaces and the symbols 
.LR $%*+-./: .
Note that all letters are converted to upper case.
Both options ignore any characters they do not recognize.
.SH SOURCE
.B /sys/src/cmd/qr.c
.SH "SEE ALSO"
International Standard ISO/IEC 18004.
.SH BUGS
The standard specifies the use of JIS-8 encoding in the default mode, however rumour has it that readers recognize UTF-8.
.PP
The more advanced coding features (Kanji mode, extended modes, switching modes midstream) are not supported.