libqrencode

Libqrencode is a library for encoding data in a QR Code symbol, a kind of 2D symbology.

Adaption of libqrencode under stewardship of Kentaro Fukuchi. Original source can be found at https://github.com/fukuchi/libqrencode

License

Re-licensed under LGPL 3.0 from previous 2.1 as permitted by the original author.

Changeset overview

Added qrprint module, defining the function QRprint_utf8, for convenience. Namespaced masking data.

Usage example

#include <stdlib.h>
#include <stdio.h>
#include <qrprint.h>

int main(void)
{
    const char* text = "https://think-biq.com";
    // Learn more about quality and version at https://www.qrcode.com/en/about/
    QRecLevel quality = QR_ECLEVEL_L;
    int version = 0;
    int casesensitive = 1;

    // Prints a UTF8 encoded QR code to stdout.
    QRprint_utf8(stdout, text, quality, version, casesensitive);

    return 0;
}

Original Main Page

Encoding

There are two methods to encode data: encoding a string/data or encoding a structured data.

Encoding a string/data

You can encode a string by calling QRcode_encodeString(). The given string is parsed automatically and encoded. If you want to encode data that can be represented as a C string style (NUL terminated), you can simply use this way.

If the input data contains Kanji (Shift-JIS) characters and you want to encode them as Kanji in QR Code, you should give QR_MODE_KANJI as a hint. Otherwise, all of non-alphanumeric characters are encoded as 8-bit data. If you want to encode a whole string in 8-bit mode, you can use QRcode_encodeString8bit() instead.

Please note that a C string can not contain NUL characters. If your data contains NUL, you must use QRcode_encodeData().

Encoding a structured data

You can construct a structured input data manually. If the structure of the input data is known, you can use this method. At first, create a ::QRinput object by QRinput_new(). Then add input data to the QRinput object by QRinput_append(). Finally call QRcode_encodeInput() to encode the QRinput data. You can reuse the QRinput object again to encode it in other symbols with different parameters.

Result

The encoded symbol is generated as a ::QRcode object. It will contain its version number, the width of the symbol, and an array represents the symbol. See ::QRcode for the details. You can free the object by QRcode_free().

Please note that the version of the result may be larger than specified. In such cases, the input data would be too large to be encoded in a symbol of the specified version.

Structured append

Libqrencode can generate "Structured-appended" symbols that enables to split a large data set into mulitple QR codes. A QR code reader concatenates multiple QR code symbols into a string. Just like QRcode_encodeString(), you can use QRcode_encodeStringStructured() to generate structured-appended symbols. This functions returns an instance of ::QRcode_List. The returned list is a singly-linked list of QRcode: you can retrieve each QR code in this way:

QRcode_List *qrcodes;
QRcode_List *entry;
QRcode *qrcode;

qrcodes = QRcode_encodeStringStructured(...);
entry = qrcodes;
while(entry != NULL) {
 qrcode = entry->code;
 // do something
 entry = entry->next;
}
QRcode_List_free(entry);

Instead of using auto-parsing functions, you can construct your own structured input. At first, instantiate an object of ::QRinput_Struct by calling QRinput_Struct_new(). This object can hold multiple ::QRinput, and one QR code is generated for a ::QRinput. QRinput_Struct_appendInput() appends a ::QRinput to a ::QRinput_Struct object. In order to generate structured-appended symbols, it is required to embed headers to each symbol. You can use QRinput_Struct_insertStructuredAppendHeaders() to insert appropriate headers to each symbol. You should call this function just once before encoding symbols.

think-biq / libqrencode