Compress face thumbnail in regular isolate

mobile/lib/services/machine_learning/face_thumbnail_generator.dart

@@ -1,12 +1,15 @@
 import 'dart:async';
 import 'dart:typed_data' show Uint8List;
 
+import "package:computer/computer.dart";
 import "package:logging/logging.dart";
 import "package:photos/models/ml/face/box.dart";
 import "package:photos/services/isolate_functions.dart";
 import "package:photos/services/isolate_service.dart";
 import "package:photos/utils/image_ml_util.dart";
 
+final Computer _computer = Computer.shared();
+
 class FaceThumbnailGenerator extends SuperIsolate {
   @override
   Logger get logger => _logger;
@@ -36,12 +39,25 @@ class FaceThumbnailGenerator extends SuperIsolate {
   ) async {
     final List<Map<String, dynamic>> faceBoxesJson =
         faceBoxes.map((box) => box.toJson()).toList();
-    return await runInIsolate(
+    final List<Uint8List> faces = await runInIsolate(
       IsolateOperation.generateFaceThumbnails,
       {
         'imagePath': imagePath,
         'faceBoxesList': faceBoxesJson,
       },
     ).then((value) => value.cast<Uint8List>());
+    final compressedFaces = <Future<Uint8List>>[];
+    for (final face in faces) {
+      if (!shouldCompressFaceThumbnail(face)) {
+        compressedFaces.add(Future.value(face));
+      } else {
+        final compressedFace = _computer.compute<Map, Uint8List>(
+          compressFaceThumbnail,
+          param: {'pngBytes': face},
+        );
+        compressedFaces.add(compressedFace);
+      }
+    }
+    return await Future.wait(compressedFaces);
   }
 }

mobile/lib/utils/image_ml_util.dart

@@ -541,19 +541,15 @@ Future<Uint8List> _cropAndEncodeCanvas(
     width: width,
     height: height,
   );
-  final pngBytes = await _encodeImageToPng(croppedImage);
-  return await _compressFaceThumbnailIfNeeded(pngBytes);
+  return await _encodeImageToPng(croppedImage);
 }
 
-/// Compresses the face thumbnail if it's too large in size.
-///
-/// Returns compressed bytes if the original size exceeds [_maxFaceThumbnailSizeBytes],
-/// otherwise returns the original bytes.
-Future<Uint8List> _compressFaceThumbnailIfNeeded(Uint8List pngBytes) async {
-  if (pngBytes.length <= _maxFaceThumbnailSizeBytes) {
-    return pngBytes;
-  }
+bool shouldCompressFaceThumbnail(Uint8List pngBytes) {
+  return pngBytes.length > _maxFaceThumbnailSizeBytes;
+}
 
+Future<Uint8List> compressFaceThumbnail(Map args) async {
+  final pngBytes = args['pngBytes'] as Uint8List;
   try {
     final compressedBytes = await FlutterImageCompress.compressWithList(
       pngBytes,