fix corner point orientation with VNBarcodeObservation

juliansteenbakker · Nov 9, 2024 · d9c2d1e · d9c2d1e
1 parent 2ac67c2
commit d9c2d1e
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Showing 4 changed files with 14 additions and 4 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -8,6 +8,7 @@
 Bugs fixed:
 * [Apple] Fixed an issue which caused the scanWindow to always be present, even when reset to no value.
 * [Apple] Fixed an issue that caused the barcode size to report the wrong height.
+* [Apple] Fixed a bug that caused the corner points to not be returned in clockwise orientation.
 
 Improvements:
 * Added a basic barcode overlay widget, for use with the camera preview.

diff --git a/darwin/mobile_scanner/Sources/mobile_scanner/MobileScannerPlugin.swift b/darwin/mobile_scanner/Sources/mobile_scanner/MobileScannerPlugin.swift
@@ -814,11 +814,12 @@ extension VNBarcodeObservation {
         let bottomRightY = (1 - bottomRight.y) * CGFloat(imageHeight)
         let bottomLeftY = (1 - bottomLeft.y) * CGFloat(imageHeight)
         let data = [
+            // Clockwise, starting from the top-left corner.
             "corners":  [
-                ["x": bottomLeftX, "y": bottomLeftY],
                 ["x": topLeftX, "y": topLeftY],
                 ["x": topRightX, "y": topRightY],
                 ["x": bottomRightX, "y": bottomRightY],
+                ["x": bottomLeftX, "y": bottomLeftY],
             ],
             "format": symbology.toInt ?? -1,
             "rawValue": payloadStringValue ?? "",

diff --git a/lib/src/objects/barcode.dart b/lib/src/objects/barcode.dart
@@ -102,10 +102,16 @@ class Barcode {
   /// The contact information that is embedded in the barcode.
   final ContactInfo? contactInfo;
 
-  /// The four corner points of the barcode,
-  /// in clockwise order, starting with the top-left point.
+  /// The corner points of the barcode.
   ///
-  /// Due to the possible perspective distortions, this is not necessarily a rectangle.
+  /// On Android, iOS and MacOS, this is a list of four points,
+  /// in clockwise direction, starting with the top left.
+  ///
+  /// On the web, the amount of points and their order
+  /// is dependent on the type of barcode that was detected.
+  ///
+  /// Due to the possible perspective distortions,
+  /// the points do not necessarily form a rectangle.
   ///
   /// This list is empty if the corners can not be determined.
   final List<Offset> corners;

diff --git a/lib/src/web/zxing/result.dart b/lib/src/web/zxing/result.dart
@@ -75,6 +75,8 @@ extension type Result(JSObject _) implements JSObject {
 
   /// Convert this result to a [Barcode].
   Barcode get toBarcode {
+    // The order of the points is dependent on the type of barcode.
+    // Don't do a manual correction here, but leave it up to the reader implementation.
     final List<Offset> corners = resultPoints;
 
     return Barcode(