[Infra] - Allow reading multiple QR codes. (Resolves #14) (#15)

Author: angelosilvestre

lib/src/goldens/golden_scenes.dart

@@ -73,6 +73,9 @@ Future<GoldenCollection> extractGoldenCollectionFromSceneWidgetTree(WidgetTester
 GoldenCollection _extractCollectionFromScene(Image sceneImage) {
   // Extract the scene metadata from the screenshot.
   final qrCode = sceneImage.readQrCode();
+  if (qrCode == null) {
+    throw Exception("Couldn't find a QR code in the golden scene image.");
+  }
   final json = JsonDecoder().convert(qrCode.text);
   final scene = GoldenSceneMetadata.fromJson(json);
 

lib/src/qr_codes/qr_code_image_scanning.dart

@@ -3,48 +3,89 @@ import 'package:zxing2/qrcode.dart';
 
 /// QR code extensions on [Image].
 extension ImageQrScanning on Image {
-  /// Attempts to find and decode a QR code within this [Image].
-  QrCode readQrCode() {
-    final rgbLuminanceSource = RGBLuminanceSource(
-      width,
-      height,
-      convert(numChannels: 4) //
-          .getBytes(order: ChannelOrder.abgr)
-          .buffer
-          .asInt32List(),
-    );
+  /// Returns the first QR code found within this [Image], or `null` if no QR code is found.
+  ///
+  /// If there are multiple QR codes in the image, it returns the first one it finds
+  /// from top to bottom.
+  QrCode? readQrCode() {
+    return _readQrCode(this);
+  }
 
-    try {
-      final binarizer = HybridBinarizer(rgbLuminanceSource);
-      final binaryBitmap = BinaryBitmap(binarizer);
-      return QRCodeReader().decode(binaryBitmap);
-    } on ReaderException {
-      // We failed to find a QR code when looking for a dark QR code
-      // on a light background. Ignore this exception and try to look
-      // for inverted colors.
-    }
+  /// Attempts to find and decode all QR codes within this [Image].
+  List<QrCode> readAllQrCodes() {
+    final qrCodes = <QrCode>[];
+
+    final image = clone();
+
+    // Keep looking for QR codes until we can't find anymore.
+    bool keepSearching = true;
+    while (keepSearching) {
+      final qrcode = _readQrCode(image);
+      if (qrcode == null) {
+        keepSearching = false;
+        continue;
+      }
+
+      qrCodes.add(qrcode);
+
+      /// Extract the rectangles from the edge points.
+      final bottomLeftRectangle = qrcode.resultPoints[0];
+      final topLeftRectangle = qrcode.resultPoints[1];
+      final topRightRectangle = qrcode.resultPoints[2];
+
+      final top = topRightRectangle.y.truncate();
+      final left = topLeftRectangle.x.truncate();
+      final right = topRightRectangle.x.truncate();
+      final bottom = bottomLeftRectangle.y.truncate();
 
-    try {
-      final binarizer = HybridBinarizer(
-        InvertedLuminanceSource(
-          rgbLuminanceSource,
-        ),
+      // Fill the QRCode region with black color to try to read other QR Codes.
+      fillRect(
+        image,
+        x1: left,
+        y1: top,
+        x2: right,
+        y2: bottom,
+        color: ColorRgb8(0, 0, 0),
       );
-      final binaryBitmap = BinaryBitmap(binarizer);
-      return QRCodeReader().decode(binaryBitmap);
-    } on ReaderException catch (exception) {
-      throw CouldNotReadQrCodeException(exception);
     }
+
+    return qrCodes;
   }
 }
 
-typedef QrCode = Result;
-
-class CouldNotReadQrCodeException implements Exception {
-  const CouldNotReadQrCodeException([this.rootCause]);
+QrCode? _readQrCode(Image image) {
+  final rgbLuminanceSource = RGBLuminanceSource(
+    image.width,
+    image.height,
+    image
+        .convert(numChannels: 4) //
+        .getBytes(order: ChannelOrder.abgr)
+        .buffer
+        .asInt32List(),
+  );
 
-  final Exception? rootCause;
+  try {
+    final binarizer = HybridBinarizer(rgbLuminanceSource);
+    final binaryBitmap = BinaryBitmap(binarizer);
+    return QRCodeReader().decode(binaryBitmap);
+  } on ReaderException {
+    // We failed to find a QR code when looking for a dark QR code
+    // on a light background. Ignore this exception and try to look
+    // for inverted colors.
+  }
 
-  @override
-  String toString() => "CouldNotReadQrCodeException";
+  try {
+    final binarizer = HybridBinarizer(
+      InvertedLuminanceSource(
+        rgbLuminanceSource,
+      ),
+    );
+    final binaryBitmap = BinaryBitmap(binarizer);
+    return QRCodeReader().decode(binaryBitmap);
+  } on ReaderException {
+    // We didn't find a QR code in the image.
+    return null;
+  }
 }
+
+typedef QrCode = Result;

test/qr_code/multiple_qrcodes.png

@@ -0,0 +1,42 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter_test_goldens/flutter_test_goldens.dart';
+
+import 'package:image/image.dart' as img;
+
+void main() {
+  group('QR Code scanning >', () {
+    test('reads single QR code from an image', () async {
+      final image = img.decodePng(File('test/qr_code/single_qrcode.png').readAsBytesSync())!;
+
+      final qrCode = image.readQrCode();
+
+      expect(qrCode, isNotNull);
+      expect(qrCode!.text, 'A QR Code');
+    });
+
+    test('reads single QR code from an image with multiple QR codes', () async {
+      final image = img.decodePng(File('test/qr_code/multiple_qrcodes.png').readAsBytesSync())!;
+
+      final qrCode = image.readQrCode();
+
+      // In top to bottom order, the third QR code is the first one.
+      expect(qrCode, isNotNull);
+      expect(qrCode!.text, 'Third QR Code');
+    });
+
+    test('reads multiple QR codes from a single image', () async {
+      final image = img.decodePng(File('test/qr_code/multiple_qrcodes.png').readAsBytesSync())!;
+
+      final qrCodes = image.readAllQrCodes();
+
+      expect(qrCodes.length, 3);
+
+      // In top to bottom order, the third QR code is the first one.
+      expect(qrCodes[0].text, 'Third QR Code');
+      expect(qrCodes[1].text, 'First QR Code');
+      expect(qrCodes[2].text, 'Second QR Code');
+    });
+  });
+}