Add dota8.yaml and O tests (#7394)

Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

ultralytics/models/yolo/obb/val.py

@@ -106,6 +106,17 @@ class OBBValidator(DetectionValidator):
                 'rbox': [round(x, 3) for x in r],
                 'poly': [round(x, 3) for x in b]})
 
+    def save_one_txt(self, predn, save_conf, shape, file):
+        """Save YOLO detections to a txt file in normalized coordinates in a specific format."""
+        gn = torch.tensor(shape)[[1, 0, 1, 0]]  # normalization gain whwh
+        for *xyxy, conf, cls, angle in predn.tolist():
+            xywha = torch.tensor([*xyxy, angle]).view(1, 5)
+            xywha[:, :4] /= gn
+            xyxyxyxy = ops.xywhr2xyxyxyxy(xywha).view(-1).tolist()  # normalized xywh
+            line = (cls, *xyxyxyxy, conf) if save_conf else (cls, *xyxyxyxy)  # label format
+            with open(file, 'a') as f:
+                f.write(('%g ' * len(line)).rstrip() % line + '\n')
+
     def eval_json(self, stats):
         """Evaluates YOLO output in JSON format and returns performance statistics."""
         if self.args.save_json and self.is_dota and len(self.jdict):