78. QR Code

Learn how to create and read QR codes.

78.1 Creating QR Codes (String)

• There are functions to create QR codes from strings as follows
• The return value is a 2D array Grid<bool> that holds QR data
  • White cells are false, black cells are true

Code	Description
QR::EncodeNumber(s)	Creates QR data from a string composed of numbers
QR::EncodeAlnum(s)	Creates QR data from a string composed of alphanumeric characters
QR::EncodeText(s)	Creates QR data from a string

• To convert a QR code represented as Grid<bool> to Image, use QR::MakeImage(qr, cellSize)
  • cellSize is the side length (pixels) of one cell. If not specified, 16 is used
  • Appropriate margins are automatically added
• Running the following sample code will create a QR code from the string Hello, Siv3D! and save it as qr.png

# include <Siv3D.hpp>

void Main()
{
	const String s = U"Hello, Siv3D!";

	// Encode string to QR code and save as image
	QR::MakeImage(QR::EncodeText(s), 10).save(U"qr.png");

	while (System::Update())
	{

	}
}

78.2 Interactive QR Code Creation (String)

• This is a sample that converts text entered in a text box to a QR code and displays it
• The QR code is recreated only when there are changes to the string

# include <Siv3D.hpp>

void Main()
{
	Window::Resize(1280, 720);
	Scene::SetBackground(ColorF{ 0.6, 0.8, 0.7 });

	// Text to convert
	TextEditState textEdit{ U"abc" };

	String previous;

	// Dynamic texture for displaying QR code
	DynamicTexture texture;

	while (System::Update())
	{
		// Text input
		SimpleGUI::TextBox(textEdit, Vec2{ 20, 20 }, 1240);

		// Recreate QR code if text is updated
		if (const String current = textEdit.text;
			current != previous)
		{
			// Convert input text to QR code
			if (const auto qr = QR::EncodeText(current))
			{
				// Update dynamic texture with scaled image
				texture.fill(QR::MakeImage(qr).scaled(Size{ 500, 500 }, InterpolationAlgorithm::Nearest));
			}

			previous = current;
		}

		texture.drawAt(640, 400);
	}
}

78.3 Creating QR Codes (Binary)

• To create QR codes from binary data, use QR::EncodeBinary(data, size)
• data is a pointer to the beginning of the binary data, size is the size of the binary data (bytes)
• The return value is a 2D array Grid<bool> that holds QR data

# include <Siv3D.hpp>

struct Data
{
	double a;
	int32 b;
	int32 c;
};

void Main()
{
	const Data data{ 1.23, 456, 789 };

	// Encode binary data to QR code and save as image
	QR::MakeImage(QR::EncodeBinary(&data, sizeof(data)), 10).save(U"qr.png");

	while (System::Update())
	{

	}
}

78.4 Reading QR Codes (String)

• QRScanner is a class for reading QR codes contained in Image
• .scanOne(image) reads up to one QR code contained in image and returns QRContent
• When the QR code encodes a string, the string is stored in QRContent::text

# include <Siv3D.hpp>

void Main()
{
	{
		QR::MakeImage(QR::EncodeText(U"Hello, Siv3D!"), 10).save(U"qr.png");
	}

	{
		const QRScanner scanner;
		const QRContent content = scanner.scanOne(Image{ U"qr.png" });

		if (content)
		{
			Print << content.text;
		}
	}

	while (System::Update())
	{

	}
}

Output

Hello, Siv3D!

78.5 Reading QR Codes (Binary)

• When the QR code encodes binary data, the binary data is stored in QRContent::binary
• The size of the binary data can be obtained with QRContent::binary.size()
• The pointer to the beginning of the binary data can be obtained with QRContent::binary.data()

# include <Siv3D.hpp>

struct Data
{
	double a;
	int32 b;
	int32 c;
};

void Main()
{
	{
		const Data data{ 1.23, 456, 789 };
		QR::MakeImage(QR::EncodeBinary(&data, sizeof(data)), 10).save(U"qr.png");
	}

	{
		const QRScanner scanner;
		const QRContent content = scanner.scanOne(Image{ U"qr.png" });

		if (content && (content.binary.size() == sizeof(Data)))
		{
			Data data;
			std::memcpy(&data, content.binary.data(), sizeof(data));
			Print << data.a << U", " << data.b << U", " << data.c;
		}
	}

	while (System::Update())
	{

	}
}

Output

1.23, 456, 789

78.6 Detecting QR Codes from Webcam Video

• The .scan() member function of QRScanner returns the contents of detected QR codes as Array<QRContent>
• See Tutorial 71 for information about webcams

# include <Siv3D.hpp>

void Main()
{
	Window::Resize(1280, 720);
	const Font font{ FontMethod::MSDF, 48 };

	AsyncTask<Webcam> task{ [=]() { return Webcam{ 0, Size{ 1280, 720 }, StartImmediately::Yes }; } };
	Webcam webcam;
	Image image;
	DynamicTexture texture;

	// QR code scanner
	const QRScanner qrScanner;

	// QR code contents
	Array<QRContent> contents;

	while (System::Update())
	{
	# if SIV3D_PLATFORM(MACOS)
		if ((not webcam) && (not task.valid()))
		{
			if (SimpleGUI::Button(U"Retry", Vec2{ 20, 20 }))
			{
				task = AsyncTask{ []() { return Webcam{ 0, Size{ 1280, 720 }, StartImmediately::Yes }; } };
			}
		}
	# endif

		if (task.isReady())
		{
			webcam = task.get();

			if (webcam)
			{
				Print << webcam.getResolution();
			}
		}

		if (webcam.hasNewFrame())
		{
			webcam.getFrame(image);

			texture.fill(image);

			// Scan QR codes
			contents = qrScanner.scan(image);
		}

		if (not webcam)
		{
			Circle{ 640, 360, 50 }.drawArc((Scene::Time() * 120_deg), 300_deg, 4, 4);
		}

		if (texture)
		{
			texture.draw();
		}

		// Visualize detected QR code positions
		for (const auto& content : contents)
		{
			content.quad.drawFrame(4, Palette::Red);

			if (content.text)
			{
				const String& text = content.text;
				font(text).region(20, content.quad.p0).stretched(10).draw(ColorF{ 1.0, 0.8 });
				font(text).draw(20, content.quad.p0, ColorF{ 0.1 });
			}
		}
	}
}