API reference

<BbScanner> events

<BbScanner> methods and properties

Task            StartAsync(string? deviceId = null)
Task            StopAsync()
void            Pause()
void            Resume()
Task            SwitchCameraAsync(string deviceId)
Task<bool>      SetTorchAsync(bool on)
Task<bool>      SetZoomAsync(double zoom)
Task            OpenFilePickerAsync()
Task<IReadOnlyList<BbCameraDevice>> GetCamerasAsync()
BbBarcodeResult?  DecodeImage(ReadOnlySpan<byte> pixels, int width, int height, BbPixelFormat format)

BbScannerStatus   Status
BbCameraInfo?     Camera
IReadOnlyList<BbCameraDevice> Cameras
BbScanDiagnostics Diagnostics
long            FramesDecoded
long            FramesWithSymbol
bool            IsTorchOn
double          Zoom
(int, int)      ProcessingSize

StartAsync is safe to call at any time: a call that arrives while an earlier one is still waiting for the permission prompt supersedes it, and the superseded request releases its camera rather than leaving it running. The same holds for StopAsync and for disposal, so navigating away mid-prompt never leaves the camera indicator lit.

BbBarcodeResult

BbScannerOptions

BbBarcodeFormat Formats                    = BbBarcodeFormat.All
BbScanRegion    Region                     = BbScanRegion.Full
int           MaxScanLines               = 15      // lines per orientation
int           DownsampleFactor           = 1
bool          TryHarder                  = false   // exhaustive detection, full rotation sweep
bool          AllowInverted              = false   // light on dark symbols
bool          TryReversedRows            = true    // linear symbols read right to left
bool          TryVerticalLines           = true    // columns and tilted lines, for rotated symbols
IReadOnlyCollection<int> ItfLengths      = 6..20 even
bool          Code39CheckDigit           = false   // require the modulo 43 check character
bool          Code39ExtendedMode         = false   // interpret Code 39 as full ASCII
TimeSpan      DuplicateSuppressionWindow = 2 seconds

BbScannerOptions.ForStillImages()   // 60 scan lines, TryHarder, AllowInverted, no suppression
options.Clone()                   // take a copy before editing a running scanner's options
options.Validate()                // throws on an out of range value

ITF has no check character, so ItfLengths is the main defence against a truncated symbol being reported as a shorter, structurally valid number. Narrow it to the lengths your application actually uses.

Headless use

The decoding pipeline has no dependency on Blazor or on a browser. It runs anywhere .NET runs, which is what makes it testable and benchmarkable.

using var decoder = new BbBarcodeDecoder(new BbScannerOptions
{
    Formats = BbBarcodeFormat.QrCode | BbBarcodeFormat.DataMatrix,
    DuplicateSuppressionWindow = TimeSpan.Zero,
});

var result = decoder.Decode(rgbaPixels, width, height, BbPixelFormat.Rgba32);
if (result is not null)
{
    Console.WriteLine($"{result.Format}: {result.Text}");
    Console.WriteLine($"took {decoder.LastFrame.Total.TotalMilliseconds:0.00} ms");
}

Extending the decoder

A new symbology implements IBbRowDecoder for a linear code or IBbMatrixDecoder for a two dimensional one. Both receive already binarised input, so a new reader only has to contribute its own character table and structure.

public interface IBbRowDecoder
{
    BbBarcodeFormat Formats { get; }
    BbSymbolDecodeResult? DecodeRow(int rowNumber, BbBitRow row, BbBarcodeFormat enabledFormats);
}

public interface IBbMatrixDecoder
{
    BbBarcodeFormat Formats { get; }
    BbSymbolDecodeResult? Decode(BbBitMatrix image, BbMatrixDecodeOptions options);
}

Binarisation is an extension point too: IBbBinarizer has one implementation tuned for matrix codes and one for linear rows, and a replacement can be substituted for either.