feat: Use native imaging for much faster thumbnail calc on mobile

lib/utils/client_manager.dart

@@ -7,6 +7,7 @@ import 'package:matrix/encryption/utils/key_verification.dart';
 import 'package:matrix/matrix.dart';
 import 'package:path_provider/path_provider.dart';
 
+import 'package:fluffychat/utils/custom_image_resizer.dart';
 import 'package:fluffychat/utils/platform_infos.dart';
 import 'famedlysdk_store.dart';
 import 'matrix_sdk_extensions.dart/fluffybox_database.dart';
@@ -99,5 +100,6 @@ abstract class ClientManager {
             AuthenticationTypes.sso
         },
         compute: compute,
+        customImageResizer: PlatformInfos.isMobile ? customImageResizer : null,
       );
 }

lib/utils/custom_image_resizer.dart

@@ -0,0 +1,32 @@
+import 'package:matrix/matrix.dart';
+import 'package:native_imaging/native_imaging.dart' as native;
+
+Future<MatrixImageFileResizedResponse?> customImageResizer(
+    MatrixImageFileResizeArguments arguments) async {
+  await native.init();
+  var nativeImg = await native.Image.loadEncoded(arguments.bytes);
+
+  final width = nativeImg.width;
+  final height = nativeImg.height;
+  final max = arguments.maxDimension;
+  if (width > max || height > max) {
+    var w = max, h = max;
+    if (width > height) {
+      h = max * height ~/ width;
+    } else {
+      w = max * width ~/ height;
+    }
+
+    final scaledImg = nativeImg.resample(w, h, native.Transform.lanczos);
+    nativeImg.free();
+    nativeImg = scaledImg;
+  }
+  final jpegBytes = await nativeImg.toJpeg(75);
+
+  return MatrixImageFileResizedResponse(
+    bytes: jpegBytes,
+    width: nativeImg.width,
+    height: nativeImg.height,
+    blurhash: arguments.calcBlurhash ? nativeImg.toBlurhash(3, 3) : null,
+  );
+}