fix: Bug with anchor parameter in Sprite.render() (#1508)

packages/flame/lib/src/sprite.dart

@@ -101,7 +101,7 @@ class Sprite {
     final drawSize = size ?? srcSize;
 
     final delta = anchor.toVector2()..multiply(drawSize);
-    final drawRect = (drawPosition + delta).toPositionedRect(drawSize);
+    final drawRect = (drawPosition - delta).toPositionedRect(drawSize);
 
     final drawPaint = overridePaint ?? paint;
 

packages/flame/test/_resources/load_image.dart

@@ -0,0 +1,9 @@
+import 'dart:io';
+import 'dart:ui';
+
+Future<Image> loadImage(String fileName) async {
+  final bytes = await File('test/_resources/$fileName').readAsBytes();
+  final codec = await instantiateImageCodec(bytes);
+  final frameInfo = await codec.getNextFrame();
+  return frameInfo.image;
+}

packages/flame/test/sprite_test.dart

@@ -0,0 +1,50 @@
+import 'dart:ui';
+
+import 'package:flame/components.dart';
+import 'package:flame/game.dart';
+import 'package:flame_test/flame_test.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '_resources/load_image.dart';
+
+void main() {
+  group('Sprite', () {
+    FlameTester(() => FlameGame()).testGameWidget(
+      'Render with anchor',
+      setUp: (game, tester) async {
+        game.add(MyComponent()..position = Vector2.all(25));
+        await game.ready();
+      },
+      verify: (game, tester) async {
+        await expectLater(
+          find.byGame<FlameGame>(),
+          matchesGoldenFile('_goldens/sprite_test_1.png'),
+        );
+      },
+    );
+  });
+}
+
+class MyComponent extends PositionComponent {
+  MyComponent() : super(size: Vector2(200, 400));
+  late final Sprite sprite;
+
+  @override
+  Future<void> onLoad() async {
+    sprite = Sprite(await loadImage('flame.png'));
+  }
+
+  @override
+  void render(Canvas canvas) {
+    canvas.drawRect(
+      size.toRect(),
+      Paint()
+        ..color = const Color(0xffffffff)
+        ..style = PaintingStyle.stroke
+        ..strokeWidth = 2,
+    );
+    // Expected: sprite is rendered in the center of the rect
+    sprite.render(canvas, position: size / 2, anchor: Anchor.center);
+  }
+}