fix(app): strip EXIF and text metadata from sent images

The image library copies EXIF through resize and orientation baking, and the JPEG/PNG encoders write it back out. Re-encoding alone therefore did not remove metadata: sent photos and their thumbnails could carry GPS coordinates, the camera model and the capture time. - Clear EXIF and text chunks on both the full image and the thumbnail right before encoding. - Treat decoder exceptions on malformed data like an undecodable image. - Add canStripMetadata() so the UI can warn before a format the library cannot read (HEIC, RAW) goes out as an untouched document.
2026-10-03 22:43:43 +02:00
parent 414d39c835
commit 4e3d7de32c
2 changed files with 90 additions and 1 deletions
@@ -0,0 +1,59 @@
+import 'dart:typed_data';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:image/image.dart' as img;
+import 'package:sepot/core/services/image_processor.dart';
+
+/// Fotka z telefonu nese v EXIF polohu (GPS), model telefonu a čas focení.
+/// Nic z toho nesmí odejít — ani v odeslané fotce, ani v jejím náhledu.
+void main() {
+  Uint8List photoWithGps({int width = 1200, int height = 800}) {
+    final photo = img.Image(width: width, height: height);
+    photo.exif.imageIfd['Make'] = 'TestPhone';
+    photo.exif.gpsIfd['GPSLatitude'] = img.IfdValueRational(50, 1);
+    return Uint8List.fromList(img.encodeJpg(photo));
+  }
+
+  bool hasExif(Uint8List jpeg) {
+    final exif = img.decodeJpgExif(jpeg);
+    return exif != null &&
+        (exif.imageIfd['Make'] != null || exif.gpsIfd['GPSLatitude'] != null);
+  }
+
+  test('vstup testu opravdu nese EXIF i GPS', () {
+    expect(hasExif(photoWithGps()), isTrue);
+  });
+
+  test('odeslaná fotka je bez EXIF a GPS', () async {
+    final out =
+        await ImageProcessor.process(photoWithGps(), mimeHint: 'image/jpeg');
+    expect(hasExif(out!.bytes), isFalse);
+  });
+
+  test('zmenšovaná fotka je bez EXIF a GPS', () async {
+    final out = await ImageProcessor.process(
+        photoWithGps(width: 4000, height: 3000),
+        mimeHint: 'image/jpeg');
+    expect(hasExif(out!.bytes), isFalse);
+  });
+
+  test('náhled je bez EXIF a GPS', () async {
+    final out =
+        await ImageProcessor.process(photoWithGps(), mimeHint: 'image/jpeg');
+    expect(hasExif(out!.thumbnailJpeg), isFalse);
+  });
+
+  test('JPEG umíme zbavit metadat', () async {
+    expect(await ImageProcessor.canStripMetadata(photoWithGps()), isTrue);
+  });
+
+  // Hlavička kontejneru HEIF z iPhonu; knihovna ho nedekóduje, takže by
+  // fotka odešla v originále — UI se musí zeptat.
+  test('HEIC metadat zbavit neumíme', () async {
+    final heic = Uint8List.fromList([
+      0, 0, 0, 24, ...'ftypheic'.codeUnits, 0, 0, 0, 0,
+      ...'mif1heic'.codeUnits, ...List.filled(64, 0),
+    ]);
+    expect(await ImageProcessor.canStripMetadata(heic), isFalse);
+  });
+}