Fix cap photo flow to always open review dialog with fallback

lib/main.dart

@@ -154,10 +154,48 @@ class _MosaicHomePageState extends State<MosaicHomePage> {
       imageQuality: 95,
       maxWidth: 1800,
     );
-    if (captured == null) return;
+    if (captured == null) {
+      debugPrint('[cap-photo] Capture cancelled by user.');
+      return;
+    }
+
+    Uint8List bytes;
+    try {
+      bytes = await captured.readAsBytes();
+    } catch (e, st) {
+      debugPrint('[cap-photo] Failed to read captured bytes: $e\n$st');
+      final fallbackImage = img.Image(width: 1, height: 1)
+        ..setPixelRgb(0, 0, 255, 152, 0);
+      bytes = Uint8List.fromList(
+        img.encodePng(fallbackImage, level: 1),
+      );
+    }
+
+    Map<String, dynamic> detected;
+    String? detectionWarning;
+    try {
+      detected = await compute(_extractCapFromPhotoIsolate, bytes);
+    } catch (e, st) {
+      debugPrint('[cap-photo] Detection isolate failed: $e\n$st');
+      detectionWarning =
+          '⚠️ Farberkennung ist fehlgeschlagen. Fallback-Farbe wird verwendet; bitte prüfen/korrigieren.';
+      final decoded = img.decodeImage(bytes);
+      final imageW = (decoded?.width ?? 1).toDouble();
+      final imageH = (decoded?.height ?? 1).toDouble();
+      final fallbackColor = Colors.orange.toARGB32();
+      detected = {
+        'dominantColor': fallbackColor,
+        'averageColor': fallbackColor,
+        'usedFallback': true,
+        'circleX': imageW / 2,
+        'circleY': imageH / 2,
+        'circleR': math.min(imageW, imageH) * 0.28,
+        'imageW': imageW,
+        'imageH': imageH,
+        'previewPng': bytes,
+      };
+    }
 
-    final bytes = await captured.readAsBytes();
-    final detected = await compute(_extractCapFromPhotoIsolate, bytes);
     if (!mounted) return;
 
     Color dominantColor = Color(detected['dominantColor'] as int);
@@ -201,23 +239,35 @@ class _MosaicHomePageState extends State<MosaicHomePage> {
               if (updateDialog) {
                 setDialogState(() {});
               }
-              final adjusted = await compute(
-                _extractCapFromAdjustedCircleIsolate,
-                <String, dynamic>{
-                  'sourceBytes': bytes,
-                  'circleX': circleX,
-                  'circleY': circleY,
-                  'circleR': circleR,
-                },
-              );
-              if (localToken != recalcToken) return;
-              dominantColor = Color(adjusted['dominantColor'] as int);
-              averageColor = Color(adjusted['averageColor'] as int);
-              previewBytes = adjusted['previewPng'] as Uint8List;
-              selected = mode == ColorExtractionMode.dominant
-                  ? dominantColor
-                  : averageColor;
-              _photoCapHexCtrl.text = _colorToHex(selected);
+              try {
+                final adjusted = await compute(
+                  _extractCapFromAdjustedCircleIsolate,
+                  <String, dynamic>{
+                    'sourceBytes': bytes,
+                    'circleX': circleX,
+                    'circleY': circleY,
+                    'circleR': circleR,
+                  },
+                );
+                if (localToken != recalcToken) return;
+                dominantColor = Color(adjusted['dominantColor'] as int);
+                averageColor = Color(adjusted['averageColor'] as int);
+                previewBytes = adjusted['previewPng'] as Uint8List;
+                selected = mode == ColorExtractionMode.dominant
+                    ? dominantColor
+                    : averageColor;
+                _photoCapHexCtrl.text = _colorToHex(selected);
+              } catch (e, st) {
+                debugPrint('[cap-photo] Recalculate failed: $e\n$st');
+                if (localToken != recalcToken) return;
+                detectionWarning =
+                    '⚠️ Aktualisierung fehlgeschlagen. Bitte Farbe manuell prüfen.';
+                const fallback = Colors.orange;
+                dominantColor = fallback;
+                averageColor = fallback;
+                selected = fallback;
+                _photoCapHexCtrl.text = _colorToHex(selected);
+              }
               if (ctx.mounted) {
                 setDialogState(() {});
               }
@@ -274,6 +324,16 @@ class _MosaicHomePageState extends State<MosaicHomePage> {
                           : 'Kreis erkannt. Direkt im Foto ziehen oder mit Pinch/Slider anpassen.',
                       style: Theme.of(context).textTheme.bodySmall,
                     ),
+                    if (detectionWarning != null) ...[
+                      const SizedBox(height: 6),
+                      Text(
+                        detectionWarning!,
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                              color: Theme.of(context).colorScheme.error,
+                              fontWeight: FontWeight.w600,
+                            ),
+                      ),
+                    ],
                     const SizedBox(height: 8),
                     SegmentedButton<ColorExtractionMode>(
                       segments: const [
@@ -1094,8 +1154,8 @@ class _CircleAdjustOverlayState extends State<_CircleAdjustOverlay> {
                 final x = (local.dx / maxW).clamp(0.0, 1.0);
                 final y = (local.dy / shownH).clamp(0.0, 1.0);
                 final scale = details.scale;
-                final r = ((_baseRadius ?? widget.circleR) * scale)
-                    .clamp(0.06, 0.49);
+                final r =
+                    ((_baseRadius ?? widget.circleR) * scale).clamp(0.06, 0.49);
                 widget.onCircleChanged(x, y, r);
               },
               onScaleEnd: (_) => _baseRadius = null,
@@ -1125,7 +1185,8 @@ class _CircleOverlayPainter extends CustomPainter {
   final double y;
   final double r;
 
-  const _CircleOverlayPainter({required this.x, required this.y, required this.r});
+  const _CircleOverlayPainter(
+      {required this.x, required this.y, required this.r});
 
   @override
   void paint(Canvas canvas, Size size) {
@@ -1154,8 +1215,10 @@ class _CircleOverlayPainter extends CustomPainter {
       ..style = PaintingStyle.stroke
       ..strokeWidth = 1
       ..color = Colors.white70;
-    canvas.drawLine(Offset(center.dx - 10, center.dy), Offset(center.dx + 10, center.dy), cross);
-    canvas.drawLine(Offset(center.dx, center.dy - 10), Offset(center.dx, center.dy + 10), cross);
+    canvas.drawLine(Offset(center.dx - 10, center.dy),
+        Offset(center.dx + 10, center.dy), cross);
+    canvas.drawLine(Offset(center.dx, center.dy - 10),
+        Offset(center.dx, center.dy + 10), cross);
   }
 
   @override