ultralytics 8.1.14 new YOLOv8-World models (#8054)

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>
Co-authored-by: UltralyticsAssistant <web@ultralytics.com>
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

ultralytics/models/yolo/model.py

@@ -1,13 +1,27 @@
 # Ultralytics YOLO 🚀, AGPL-3.0 license
 
+from pathlib import Path
+
 from ultralytics.engine.model import Model
 from ultralytics.models import yolo
-from ultralytics.nn.tasks import ClassificationModel, DetectionModel, OBBModel, PoseModel, SegmentationModel
+from ultralytics.nn.tasks import ClassificationModel, DetectionModel, OBBModel, PoseModel, SegmentationModel, WorldModel
+from ultralytics.utils import yaml_load, ROOT
 
 
 class YOLO(Model):
     """YOLO (You Only Look Once) object detection model."""
 
+    def __init__(self, model="yolov8n.pt", task=None, verbose=False):
+        """Initialize YOLO model, switching to YOLOWorld if model filename contains '-world'."""
+        stem = Path(model).stem  # filename stem without suffix, i.e. "yolov8n"
+        if "-world" in stem:
+            new_instance = YOLOWorld(model)
+            self.__class__ = type(new_instance)
+            self.__dict__ = new_instance.__dict__
+        else:
+            # Continue with default YOLO initialization
+            super().__init__(model=model, task=task, verbose=verbose)
+
     @property
     def task_map(self):
         """Map head to model, trainer, validator, and predictor classes."""
@@ -43,3 +57,49 @@ class YOLO(Model):
                 "predictor": yolo.obb.OBBPredictor,
             },
         }
+
+
+class YOLOWorld(Model):
+    """YOLO-World object detection model."""
+
+    def __init__(self, model="yolov8s-world.pt") -> None:
+        """
+        Initializes the YOLOv8-World model with the given pre-trained model file. Supports *.pt and *.yaml formats.
+
+        Args:
+            model (str): Path to the pre-trained model. Defaults to 'yolov8s-world.pt'.
+        """
+        super().__init__(model=model, task="detect")
+
+        # Assign default COCO class names
+        self.model.names = yaml_load(ROOT / "cfg/datasets/coco8.yaml").get("names")
+
+    @property
+    def task_map(self):
+        """Map head to model, validator, and predictor classes."""
+        return {
+            "detect": {
+                "model": WorldModel,
+                "validator": yolo.detect.DetectionValidator,
+                "predictor": yolo.detect.DetectionPredictor,
+            }
+        }
+
+    def set_classes(self, classes):
+        """
+        Set classes.
+
+        Args:
+            classes (List(str)): A list of categories i.e ["person"].
+        """
+        self.model.set_classes(classes)
+        # Remove background if it's given
+        background = " "
+        if background in classes:
+            classes.remove(background)
+        self.model.names = classes
+
+        # Reset method class names
+        # self.predictor = None  # reset predictor otherwise old names remain
+        if self.predictor:
+            self.predictor.model.names = classes