5.6 Two-Dimensional Symbols

5.6.1 Data Matrix (ISO 16022)

Also known as Semacode this symbology can encode a large amount of data in a small area. Any length ASCII string can be encoded up to 780 characters. Symbol size is determined by the length of the input data and Reed-Solomon error correction is added.

5.6.2 QR Code (ISO 18004)

Also known as Quick Response Code this symbology was developed by Denso. QR Code support in Zint relies on libqrencode (version 2.0.0 or later) which is available from http://megaui.net/fukuchi/works/qrencode/index.en.html. Support for QR Code through libzint means that developers only need to write handlers for one API which covers QR Code as well as all of the other code symbologies provided by libzint. Four levels of error correction are available using the security= option or setting option_1 as shown in the following table.

Input	ECC Level	Error Correction Capacity	Recovery Capacity
1	L (default)	Approx 20% of symbol	Approx 7%
2	M	Approx 37% of symbol	Approx 15%
3	Q	Approx 55% of symbol	Approx 25%
4	H	Approx 65% of symbol	Approx 30%

The size of the symbol can be set by using the vers= option or setting option_2 to the QR Code version required (1-40). The maximum capacity of a (version 40) QR Code symbol is 7089 numeric digits, 4296 alphanumeric characters or 2953 bytes of data.

5.6.3 Maxicode (ISO 16023)

Developed by UPS the Maxicode symbology employs a grid of hexagons surrounding a 'bulls-eye' finder pattern. This symbology is designed for the identification of parcels. Zint encodes Maxicode symbols in Mode 2 or Mode 3 depending on the postcode data entered. In these modes Maxicode symbols are composed of two parts named the primary and secondary messages. The primary message consists of a structured data field which includes various data about the package being sent, the secondary message usually consists of address data in a data structure. The format of the primary message is given in the following table:

The primary message can be designated at the command prompt using the --primary= switch. The secondary message uses the normal data entry method. For example:

zint -o test.eps -b 57 --primary='999999999840012' -d 'Secondary Message Here'

When using the API the primary message must be placed in the symbol->primary string. The secondary is entered in the same way as described in section 4.2.

Modes 4 to 6 can be encoded using the --mode= switch or by setting option_1. Modes 4 to 6 do not require a primary message. For example:

zint -o test.eps -b 57 --mode=4 -d 'A MaxiCode Message in Mode 4'

Mode 6 is reserved for the maintenance of scanner hardware and should not be used to encode user data. All modes support extended ASCII characters and number compression. The maximum length of text which can be placed in a Maxicode symbol depends on the type of characters used in the text. Example maximum data lengths are given in the table below:

PLEASE NOTE that due to the unique style of the Maxicode symbol not all of the options available for other symbologies are available. Settings for height, whitespace width, border width and output options will be ignored. Colour options are available as with other symbologies. PNG output is set at a resolution of 12 pixels per millimetre (approx 300 dpi) and uses the methods set out in Annex J of the ISO/IEC standard.

5.6.4 Aztec Code (ISO 24778)

Invented by Andrew Longacre at Welch Allyn Inc in 1995 the Aztec Code symbol is a matrix symbol with a distinctive bulls-eye finder pattern. Zint can generate Compact Aztec Code (sometimes called Small Aztec Code) as well as “full-range” Aztec Code symbols and by default will automatically select symbol type and size dependent on the length of the data to be encoded. Error correction codewords will normally be generated to fill at least 23% of the symbol. Two options are available to change this behaviour:

The size of the symbol can be specified using the --ver= switch followed by (or setting option_2 to) a value between 1 and 36 according to the following table:

Value Entered	Symbol Generated
1-4	Compact Aztec Code with [value] layers
5-36	“Full-Range” Aztec Code with [value – 4] layers

Note that in symbols which have a specified size the amount of error correction is dependent on the length of the data input and Zint will allow error correction capacities as low as 3 codewords.

Alternatively the amount of error correction data can be specified by use of the --mode= switch followed by (or setting option_1 to) a value from the following table:

Mode	Error Correction Capacity
1	>10% + 3 codewords
2	>23% + 3 codewords
3	>36% + 3 codewords
4	>50% + 3 codewords

It is not possible to select both symbol size and error correction capacity for the same symbol. If both options are selected then the error correction capacity selection will be ignored.

Aztec Code is able to encode any extended ASCII character data up to a maximum length of approximately 3823 numeric or 3067 alphabetic characters or 1914 bytes of data.