Help language development. Donate to The Perl Foundation

Image::QRCode cpan:FRITH last updated on 2019-08-11

Image::QRCode

Image::QRCode - An interface to libqrencode.

Build Status

Operating System	Build Status	CI Provider
Linux		Travis CI

Example

my $code = Image::QRCode.new.encode('https://perl6.org/');
my $dim = $code.qrcode.width;
my @array2D[$dim;$dim] = $code.get-data(2);
say @array2D.shape;
say @array2D;
my @array1D = $code.get-data(1);
say @array1D;

use Image::QRCode;

Image::QRCode.new.encode('https://perl6.org/').termplot;

For more examples see the example directory.

Description

Image::QRCode provides an interface to libqrencode and allows you to generate a QR Code.

Documentation

new(Int :$.version, Int :$.level, Int :$.mode, Int :$.casesensitive, Int :$.size)

Creates an Image::QRCode object. It may take a list of optional arguments.

The optional argument $version defaults to 0 (auto-select). The maximum version value is 4.

The optional argument $level defaults to QR_ECLEVEL_L. The list of possible values for this argument is provided by the QRecLevel enum:

• QR_ECLEVEL_L # lowest
• QR_ECLEVEL_M
• QR_ECLEVEL_Q
• QR_ECLEVEL_H # highest

The optional argument $mode defaults to QR_MODE_8. The list of possible values for this argument is provided by the QRencodeMode enum:

• QR_MODE_NUL # Terminator (NUL character). Internal use only
• QR_MODE_NUM # Numeric mode
• QR_MODE_AN # Alphabet-numeric mode
• QR_MODE_8 # 8-bit data mode
• QR_MODE_KANJI # Kanji (shift-jis) mode
• QR_MODE_STRUCTURE # Internal use only
• QR_MODE_ECI # ECI mode
• QR_MODE_FNC1FIRST # FNC1, first position
• QR_MODE_FNC1SECOND # FNC1, second position

The optional argument $casesensitive defaults to True.

The optional argument $size defaults to 2. This argument is used only when generating a character based plot of the QR code to adjust the relative proportion of width vs. height.

All these arguments can be accessed directly for both reading and writing:

my Image::QRCode $code .= new;
$code.casesensitive = False;

encode(Str $text!, Int :$version, Int :$level, Int :$mode, Int :$casesensitive)

Encodes a string. It takes one mandatory argument: text, the string to encode. All the other arguments are optional.

This method put a QR code in the attribute qrcode, an object of class QRcode, which can be read directly or managed by other methods.

The class QRcode is an interface to the library's internal structure of a QR code. It has three attributes:

• int32 $.version
• int32 $.width
• CArray[uint8] $.data

Even if the data attribute can be accessed directly, its representation is a bit complex and most of the coded information is not very useful. The original library's documentation goes as follows:

Symbol data is represented as an array contains width*width uchars.
Each uchar represents a module (dot). If the less significant bit of
the uchar is 1, the corresponding module is black. The other bits are
meaningless for usual applications, but here its specification is described.

MSB 76543210 LSB
    |||||||`- 1=black/0=white
    ||||||`-- data and ecc code area
    |||||`--- format information
    ||||`---- version information
    |||`----- timing pattern
    ||`------ alignment pattern
    |`------- finder pattern and separator
    `-------- non-data modules (format, timing, etc.)

get-data($dimension)

This method returns the QR code data, encoded as a 1D or 2D array. The argument dimension can be 1 or 2: passing a dimension = 1 the method returns a linear array of the values of all the dots, coded as 0 (black) or 1 (white). A value of 2 makes the method return an array of arrays.

termplot(Int :$size)

This method accepts the optional parameter size, which determines the orizontal stretch of the "image". It prints the QR code on the terminal screen as \c[FULL BLOCK] characters. It returns a Failure object if there's no data to plot.

Low level calls

This module provides an interface to all the C library's functions. The library's full documentation can be found here:

https://fukuchi.org/works/qrencode/manual/index.html

Its GitHub page is:

https://github.com/fukuchi/libqrencode

When using the low level calls, keep in mind that old versions of the library may lack some functionality:

• pre v3.2.1 (2012) have no way to query the API version.
• pre 2010-01-27 versions lack full ECI support (QRinput_encodeModeECI(), QRinput_appendECIheader(), QRinput_estimateBitsModeECI()).
• pre 2010-01-16 versions have no QRcode_encodeDataMQR() and QRcode_encodeDataStructured() calls.

Prerequisites

This module requires the libqrencode4 library to be installed. In case one has any API-compatible version, this module also reads the dynamically-assigned environment variable PERL6_QRENCODE_LIB. For example

PERL6_QRENCODE_LIB=libqrencode.so.3 ./program.p6

For the installation please follow the instructions below, based on your platform:

Debian Linux

sudo apt-get install libqrencode4

Installation

To install it using zef (a module management tool):

$ zef update
$ zef install Image::QRCode

Testing

To run the tests:

$ prove -e "perl6 -Ilib"

Note

Image::QRCode relies on a C library which might not be present in one's installation, so it's not a substitute for a pure Perl6 module.

Author

Fernando Santagata

Copyright and license

The Artistic License 2.0