QRCodeImageReader Class

Namespace: Meziantou.Framework.Imaging.Barcodes
Assembly: Meziantou.Framework.Imaging.Barcodes.dll
Package: Meziantou.Framework.Imaging.Barcodes 1.0.10
Source: QRCodeImageReader.cs
Available in package assets: net10.0net11.0

Provides methods to read the QR codes of an image: standard QR codes, Micro QR codes and rMQR codes.

public static class QRCodeImageReader

Methods

Name	Description
ReadQRCodes(Image, QRCodeReadingOptions?, CancellationToken)	Reads the QR codes of an image.

ReadQRCodes(Image, QRCodeReadingOptions?, CancellationToken)

QRCodeImageReader.cs

Reads the QR codes of an image.

public static IReadOnlyList<QRCodeImageResult> ReadQRCodes(this Image image, QRCodeReadingOptions? options = null, CancellationToken cancellationToken = default)

Parameters

image Image: The image. For an animated image, its first frame is read.
options QRCodeReadingOptions?: The reading options, or null for the defaults.
cancellationToken CancellationToken: A token to cancel the reading.

Returns

IReadOnlyList<QRCodeImageResult> The QR codes found, each once; empty when there is none.

Exceptions

ArgumentNullException: image is null.
OperationCanceledException: cancellationToken was canceled.

Remarks

The reader is made for clean images: generated, printed or scanned symbols, photographed straight on. It finds the finder patterns of the symbols, which can be rotated, scaled, slightly blurred or in mild perspective, samples their modules and decodes them with QRCodeDecoder. A transparent background reads as white.

A symbol needs its quiet zone and modules of at least 2 pixels. The pixels are classified as dark or light with the Otsu threshold of the image, then with a local threshold (Sauvola) when no symbol is found.

Example

using var image = QRCode.Create("https://www.meziantou.net").ToImage(); // or Image.Load("photo.png")

var results = image.ReadQRCodes();

var result = Assert.Single(results);
Assert.Equal("https://www.meziantou.net", result.Text);

// The corners of the symbol in the image: top-left, top-right, bottom-right, bottom-left
var topLeft = result.Corners[0];
Assert.True(topLeft.DistanceTo(new PointD(40, 40)) < 1); // after the quiet zone of 4 modules of 10 pixels