Single computer call for compression

mobile/lib/services/machine_learning/face_thumbnail_generator.dart

@@ -46,14 +46,13 @@ class FaceThumbnailGenerator extends SuperIsolate {
         'faceBoxesList': faceBoxesJson,
       },
     ).then((value) => value.cast<Uint8List>());
-    final compressedFaces = <Future<Uint8List>>[];
-    for (final face in faces) {
-      final compressedFace = _computer.compute<Map, Uint8List>(
-        compressFaceThumbnail,
-        param: {'pngBytes': face},
-      );
-      compressedFaces.add(compressedFace);
-    }
-    return await Future.wait(compressedFaces);
+    final compressedFaces = await _computer.compute<Map, List<Uint8List>>(
+      compressFaceThumbnails,
+      param: {'listPngBytes': faces},
+    );
+    _logger.fine(
+      "Compressed face thumbnails from sizes ${faces.map((e) => e.length / 1024).toList()} to ${compressedFaces.map((e) => e.length / 1024).toList()} kilobytes",
+    );
+    return compressedFaces;
   }
 }

mobile/lib/utils/image_ml_util.dart

@@ -543,30 +543,28 @@ Future<Uint8List> _cropAndEncodeCanvas(
   return await _encodeImageToPng(croppedImage);
 }
 
-Future<Uint8List> compressFaceThumbnail(Map args) async {
-  final pngBytes = args['pngBytes'] as Uint8List;
+Future<List<Uint8List>> compressFaceThumbnails(Map args) async {
+  final listPngBytes = args['listPngBytes'] as List<Uint8List>;
+  final List<Future<Uint8List>> compressedBytesList = [];
   try {
-    final compressedBytes = await FlutterImageCompress.compressWithList(
-      pngBytes,
-      quality: _faceThumbnailCompressionQuality,
-      format: CompressFormat.jpeg,
-      minWidth: _faceThumbnailMinDimension,
-      minHeight: _faceThumbnailMinDimension,
-    );
-
-    _logger.info(
-      'Face thumbnail compressed from ${pngBytes.length} bytes to ${compressedBytes.length} bytes '
-      '(${((1 - compressedBytes.length / pngBytes.length) * 100).toStringAsFixed(1)}% reduction)',
-    );
-
-    return compressedBytes;
+    for (final pngBytes in listPngBytes) {
+      final compressedBytes = FlutterImageCompress.compressWithList(
+        pngBytes,
+        quality: _faceThumbnailCompressionQuality,
+        format: CompressFormat.jpeg,
+        minWidth: _faceThumbnailMinDimension,
+        minHeight: _faceThumbnailMinDimension,
+      );
+      compressedBytesList.add(compressedBytes);
+    }
+    return await Future.wait(compressedBytesList);
   } catch (e, s) {
     _logger.warning(
-      'Failed to compress face thumbnail, using original. Size: ${pngBytes.length} bytes',
+      'Failed to compress face thumbnail, using original. Size: ${listPngBytes.map((e) => e.length).toList()} bytes',
       e,
       s,
     );
-    return pngBytes;
+    return listPngBytes;
   }
 }