qzxing

Qt/QML wrapper library for the ZXing barcode image processing library.

Supports barcode decoding for the following types:

• UPC-A
• UPC-E
• EAN-8
• EAN-13
• ITF
• Code 39
• Code 93
• Code 128 (GS1)
• Codabar
• QR Code
• Data Matrix
• Aztec (beta)
• PDF 417

Supports barcode encoding for the following types:

• QR Code

Table of contents

1. How to include
   1. Embed the source code
   2. Compile the project as an external library
   3. Control dependencies
      1. QZXing (core)
      2. QZXing (core + QML)
      3. QZXing + QZXingFilter
2. How to use
   1. Decoding operation
      1. C++/Qt
      2. Qt Quick
   2. Encoding operation
      1. C++/Qt
      2. Qt Quick
   3. Encoded text format Information
3. Unit test dependency
4. Contact

How to include

The project can be used in two ways:

Embed the source code.

Copy source code folder of QZXing to the root of your project. Add the following line to your .pro file. For more information see here.

include(QZXing/QZXing.pri)

Compile the project as an external library

Open QZXing project (QZXing.pro) and compile. If it is needed to compile as static library, uncomment the following line in the .pro file.

CONFIG += staticlib

Control dependencies

Project file config tags are now introduced to be able to control the dependencies of the library accoring to the needs. The core part requires only "core" and "gui" Qt modules. Though for backward compatibility "quick" Qt module is also required. The 3 level of dependencies are:

QZXing (core)

By including QZXing.pri or by building QZXing.pro you get the core functionality of QZXing which requires only QtCore and QtGui (because of QImage).

Warning! The initial default configuration till 20/03/2017 was including qzxing_qml. This tag could not be removed once added, so it was needed to be removed from the defaults.

QZXing (core + QML)

If an application is going to use QML functionality, it is now possible to add the dependency to it. This can be done by adding the folloing line to the .pro file of its project:

CONFIG += qzxing_qml

QZXing + QZXingFilter

QZXing includes QZXingFilter, a QAbstractVideoFilter implementation to provide a mean of providing live feed to the decoding library. It automatically includes QML implementation as well. This option requires "multimedia" Qt module this is why it is considered as a separate configuration. It can be used by adding the folloing line to the .pro file of a project:

CONFIG += qzxing_multimedia

How to use

Follows simple code snippets that brefly show the use of the library. For more details advise the examples included in the repository and the wiki.

Decoding operation

C++/Qt

#include "QZXing.h"

int main() 
{
	QImage imageToDecode("file.png");
	QZXing decoder;
	decoder.setDecoder( DecoderFormat_QR_CODE | DecoderFormat_EAN_13 );
	QString result = decoder.decodeImage(imageToDecode);
}

Qt Quick

First register QZXing type to the QML engine.

#include "QZXing.h"

int main() 
{
	...
	QZXing::registerQMLTypes();
	...
}

The in the QML file

import QZXing 2.3

function decode(preview) {
	imageToDecode.source = preview
	decoder.decodeImageQML(imageToDecode);
}

Image{
	id:imageToDecode
}

QZXing{
	id: decoder

	enabledDecoders: QZXing.DecoderFormat_QR_CODE

	onDecodingStarted: console.log("Decoding of image started...")

	onTagFound: console.log("Barcode data: " + tag)

	onDecodingFinished: console.log("Decoding finished " + (succeeded==true ? "successfully" :    "unsuccessfully") )
}

Encoding operation

C++/Qt

The encoding function has been written as static as it does not have any dependencies to data other than the ones provided by the arguments.

Use the encoding function with its default settings:

• Format: QR Code
• Size: 240x240
• Error Correction Level: Low (L)

#include "QZXing.h"

int main() 
{
    QString data = "text to be encoded";
    QImage barcode = QZXing::encodeData(data);
}    

Or use the encoding function with custom settings:

QString data = "text to be encoded";
QImage barcode = QZXing::encodeData(data, QZXing::EncoderFormat_QR_CODE,
								QSize(width.toInt(), height.toInt()), QZXing::EncodeErrorCorrectionLevel_H);

Qt Quick

The encoding function can be easily used in QML through QZXing's Image Provider: "image://QZXing/encode/<data_to_be_encoded>". As with the C++ example, it can either be used with the default settings or with custom settings.

Default settings:

import QZXing 2.3

TextField {
	id: inputField
	text: "Hello world!"
}

Image{
	source: "image://QZXing/encode/" + inputField.text;
	cache: false;
}

Or use the encoding function with the optional custom settings that are passed like URL query parameters:

attribute name	value	description
border	true, false	image has border (white 1px)
correctionLevel	L, M, Q, H	the error correction level
format	qrcode	the encode formatter. Currently only QR Code.
transparent	true, false	whether the black pixels are transparent

the size of the image can be adjusted by using the Image.sourceWidth and Image.sourceHeight properties of Image QML element.

import QZXing 2.3

TextField {
	id: inputField
	text: "Hello world!"
}

Image{
	source: "image://QZXing/encode/" + inputField.text +
					"?correctionLevel=M" +
					"&format=qrcode"
	sourceSize.width: 320
	sourceSize.height: 320
}

Encoded text format Information

Here is a list of contents that have been encoded and tested to be recognizable by the Android ZXing decoding application: QR Code encoding wiki page

Unit test dependency

In order to run Unit tests in /test folder, the git submodule containing the test resoucres needs to be initialized and/or updated:

cd qzxing
git submodule update --init --recursive

Contact

In case of bug reports or feature requests feel free to open an issue.