fix: Crash on iOS devices with half image cropping

packages/smooth_app/lib/pages/scan/camera_image_cropper.dart

@@ -1,68 +1,156 @@
+import 'dart:io';
 import 'dart:typed_data';
+
 import 'package:camera/camera.dart';
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:google_ml_barcode_scanner/google_ml_barcode_scanner.dart';
 import 'package:smooth_app/pages/scan/abstract_camera_image_getter.dart';
 import 'package:typed_data/typed_buffers.dart';
 
 /// Camera Image Cropper, in order to limit the barcode scan computations.
 ///
+/// Note: on iOS, we can only crop the size, as the coordinates are hardcoded.
+/// [width01] and [height01] are thus ignored on this platform.
+///
 /// Use CameraController with imageFormatGroup: ImageFormatGroup.yuv420
 /// [left01], [top01], [width01] and [height01] are values between 0 and 1
 /// that delimit the cropping area.
 /// For instance:
 /// * left01: 0, top01: 0, width01: 1, height01: .2 delimit the top 20% banner
 /// * left01: .5, top01: .5, width01: .5, height01: ..5 the bottom right rect
-class CameraImageCropper extends AbstractCameraImageGetter {
-  CameraImageCropper(
+abstract class CameraImageCropper extends AbstractCameraImageGetter {
+  factory CameraImageCropper(
+    final CameraImage cameraImage,
+    final CameraDescription cameraDescription, {
+    required double left01,
+    required double top01,
+    required double width01,
+    required double height01,
+  }) {
+    if (Platform.isIOS) {
+      return _CameraImageCropperImplIOS(
+        cameraImage,
+        cameraDescription,
+        width01: width01,
+        height01: height01,
+      );
+    } else {
+      return _CameraImageCropperImplDefault(
+        cameraImage,
+        cameraDescription,
+        left01: left01,
+        top01: top01,
+        width01: width01,
+        height01: height01,
+      );
+    }
+  }
+
+  CameraImageCropper._(
     final CameraImage cameraImage,
     final CameraDescription cameraDescription, {
-    required this.left01,
-    required this.top01,
     required this.width01,
     required this.height01,
-  }) : super(cameraImage, cameraDescription) {
+  })  : assert(width01 > 0 && width01 <= 1),
+        assert(height01 > 0 && height01 <= 1),
+        super(
+          cameraImage,
+          cameraDescription,
+        ) {
     _computeCropParameters();
   }
 
-  final double left01;
-  final double top01;
   final double width01;
   final double height01;
-  late int _left;
-  late int _top;
+
   late int _width;
   late int _height;
 
   void _computeCropParameters() {
-    assert(width01 > 0 && width01 <= 1);
-    assert(height01 > 0 && height01 <= 1);
+    if (orientation == 0) {
+      _width = _computeWidth();
+      _height = _computeHeight();
+    } else if (orientation == 90) {
+      _width = _computeWidth();
+      _height = _computeHeight();
+    } else {
+      throw Exception('Orientation $orientation not dealt with for the moment');
+    }
+  }
+
+  int _computeWidth() {
+    if (orientation == 0) {
+      return _getEven(fullWidth * width01);
+    } else if (orientation == 90) {
+      return _getEven(fullWidth * height01);
+    }
+
+    throw Exception('Orientation $orientation not dealt with for the moment');
+  }
+
+  int _computeHeight() {
+    if (orientation == 0) {
+      return _getEven(fullHeight * height01);
+    } else if (orientation == 90) {
+      return _getEven(fullHeight * width01);
+    }
+
+    throw Exception('Orientation $orientation not dealt with for the moment');
+  }
+
+  int _getEven(final double value) => 2 * (value ~/ 2);
+
+  int get fullWidth => cameraImage.width;
+
+  int get fullHeight => cameraImage.height;
+
+  int get orientation => cameraDescription.sensorOrientation;
+
+  @override
+  Size getSize() => Size(
+        _width.toDouble(),
+        _height.toDouble(),
+      );
+}
+
+class _CameraImageCropperImplDefault extends CameraImageCropper {
+  _CameraImageCropperImplDefault(
+    final CameraImage cameraImage,
+    final CameraDescription cameraDescription, {
+    required this.left01,
+    required this.top01,
+    required double width01,
+    required double height01,
+  }) : super._(
+          cameraImage,
+          cameraDescription,
+          width01: width01,
+          height01: height01,
+        );
+
+  final double left01;
+  final double top01;
+  late int _left;
+  late int _top;
+
+  @override
+  void _computeCropParameters() {
+    super._computeCropParameters();
     assert(left01 >= 0 && left01 < 1);
     assert(top01 >= 0 && top01 < 1);
     assert(left01 + width01 <= 1);
     assert(top01 + height01 <= 1);
 
-    final int fullWidth = cameraImage.width;
-    final int fullHeight = cameraImage.height;
-    final int orientation = cameraDescription.sensorOrientation;
-
-    int _getEven(final double value) => 2 * (value ~/ 2);
-
     if (orientation == 0) {
-      _width = _getEven(fullWidth * width01);
-      _height = _getEven(fullHeight * height01);
       _left = _getEven(fullWidth * left01);
       _top = _getEven(fullHeight * top01);
-      return;
-    }
-    if (orientation == 90) {
-      _width = _getEven(fullWidth * height01);
-      _height = _getEven(fullHeight * width01);
+    } else if (orientation == 90) {
       _left = _getEven(fullWidth * top01);
       _top = _getEven(fullHeight * left01);
-      return;
+    } else {
+      throw Exception('Orientation $orientation not dealt with for the moment');
     }
-    throw Exception('Orientation $orientation not dealt with for the moment');
   }
 
   // cf. https://en.wikipedia.org/wiki/YUV#Y′UV420p_(and_Y′V12_or_YV12)_to_RGB888_conversion
@@ -73,7 +161,10 @@ class CameraImageCropper extends AbstractCameraImageGetter {
   };
 
   @override
-  Size getSize() => Size(_width.toDouble(), _height.toDouble());
+  Size getSize() => Size(
+        _width.toDouble(),
+        _height.toDouble(),
+      );
 
   @override
   Uint8List getBytes() {
@@ -125,3 +216,49 @@ class CameraImageCropper extends AbstractCameraImageGetter {
     return planeData;
   }
 }
+
+/// On iOS, coordinates are hardcoded in the native code (0, 0)
+/// [https://github.com/danjodanjo/google_ml_barcode_scanner/blob/master/ios/Classes/MLKVisionImage%2BFlutterPlugin.m#L136]
+///
+/// The only crop we can do is to shrink the width and/or the height
+class _CameraImageCropperImplIOS extends CameraImageCropper {
+  _CameraImageCropperImplIOS(
+    final CameraImage cameraImage,
+    final CameraDescription cameraDescription, {
+    required double width01,
+    required double height01,
+  })  : assert(width01 > 0 && width01 <= 1),
+        assert(height01 > 0 && height01 <= 1),
+        super._(
+          cameraImage,
+          cameraDescription,
+          width01: width01,
+          height01: height01,
+        );
+
+  // Same implementation as [CameraImageFullGetter]
+  @override
+  Uint8List getBytes() {
+    final WriteBuffer allBytes = WriteBuffer();
+    for (final Plane plane in cameraImage.planes) {
+      allBytes.putUint8List(plane.bytes);
+    }
+    return allBytes.done().buffer.asUint8List();
+  }
+
+  // Same implementation as [CameraImageFullGetter]
+  @override
+  List<InputImagePlaneMetadata> getPlaneMetaData() {
+    final List<InputImagePlaneMetadata> planeData = <InputImagePlaneMetadata>[];
+    for (final Plane plane in cameraImage.planes) {
+      planeData.add(
+        InputImagePlaneMetadata(
+          bytesPerRow: plane.bytesPerRow,
+          height: plane.height,
+          width: plane.width,
+        ),
+      );
+    }
+    return planeData;
+  }
+}