Site map  

Sput's QR

Sput QR

The above image was made with qrencode (which is also available as Debian package). It's a 21x21 'binary' QR code which contains the text 'http://sput.nl' and has error correction level 'M'.

Using upper case only can reduce the amount of data. And sometimes a single character can make a difference, as can be seen below;

QR Sizes
URL: HTTP://SPUT.NL/ http://sput.nl http://sput.nl/ http://www.sput.nl/
ECLSize
L21x2121x2121x2125x25
M21x2121x2125x2525x25
Q21x2125x2525x2525x25
H25x2525x2529x2929x29

Error correction levels;

L 7 %
M15 %
Q25 %
H30 %

And some of these images;

AlphanumericBinaryBinary
SPUT.NL QR sput.nl QR www.sput.nl QR
HTTP://SPUT.NL/ http://sput.nl/ http://www.sput.nl/

Note: All the QRs above have error correction level 'Q'.

Most webbrowsers convert 'HTTP' into 'http', hostnames are case insensitive and my webserver redirects 'sput.nl' to 'www.sput.nl'.
Not all QR readers support upper case URLs, but most do. Files and paths are case sensitive though. So HTTP://EXAMPLE.COM/FOO/BAR and HTTP://EXAMPLE.COM/foo/bar are not the same thing!
Once you have decided on a text, keep increasing the error correction level (ECL), until the file increases in size. The ECL just before that is probably your best choice. These are shown bold in the table above. Some QR encoding programs will do this optimisation for you.
If you want to use non-ASCII in a QR you need ECI (Extended Channel Interpretation); Some QR encoding programs default to UTF-8.
For non-ASCII in URLs you need to replace the individual bytes in each UTF-8 multi-byte sequence by percent-hex-value. E.G.: '%C3%BC' for 'ΓΌ'. So URLs are always US-ASCII! Most browsers will translate these sequences back to UTF-8 and display this instead.
QRs need a boundary called quiet zone around them. The minimum required quiet zone has width of one. Recommended is four. Qrencode will create this boundary for you.

More info;