Reference for ultralytics/models/yolo/pose/val.py

def eval_json(self, stats):
    """Evaluate object detection model using COCO JSON format."""
    if self.args.save_json and self.is_coco and len(self.jdict):
        anno_json = self.data["path"] / "annotations/person_keypoints_val2017.json"  # annotations
        pred_json = self.save_dir / "predictions.json"  # predictions
        LOGGER.info(f"\nEvaluating pycocotools mAP using {pred_json} and {anno_json}...")
        try:  # https://github.com/cocodataset/cocoapi/blob/master/PythonAPI/pycocoEvalDemo.ipynb
            check_requirements("pycocotools>=2.0.6")
            from pycocotools.coco import COCO  # noqa
            from pycocotools.cocoeval import COCOeval  # noqa

            for x in anno_json, pred_json:
                assert x.is_file(), f"{x} file not found"
            anno = COCO(str(anno_json))  # init annotations api
            pred = anno.loadRes(str(pred_json))  # init predictions api (must pass string, not Path)
            for i, eval in enumerate([COCOeval(anno, pred, "bbox"), COCOeval(anno, pred, "keypoints")]):
                if self.is_coco:
                    eval.params.imgIds = [int(Path(x).stem) for x in self.dataloader.dataset.im_files]  # im to eval
                eval.evaluate()
                eval.accumulate()
                eval.summarize()
                idx = i * 4 + 2
                stats[self.metrics.keys[idx + 1]], stats[self.metrics.keys[idx]] = eval.stats[
                    :2
                ]  # update mAP50-95 and mAP50
        except Exception as e:
            LOGGER.warning(f"pycocotools unable to run: {e}")
    return stats

def get_desc(self):
    """Return description of evaluation metrics in string format."""
    return ("%22s" + "%11s" * 10) % (
        "Class",
        "Images",
        "Instances",
        "Box(P",
        "R",
        "mAP50",
        "mAP50-95)",
        "Pose(P",
        "R",
        "mAP50",
        "mAP50-95)",
    )

def init_metrics(self, model):
    """Initialize pose estimation metrics for YOLO model."""
    super().init_metrics(model)
    self.kpt_shape = self.data["kpt_shape"]
    is_pose = self.kpt_shape == [17, 3]
    nkpt = self.kpt_shape[0]
    self.sigma = OKS_SIGMA if is_pose else np.ones(nkpt) / nkpt
    self.stats = dict(tp_p=[], tp=[], conf=[], pred_cls=[], target_cls=[], target_img=[])

def plot_predictions(self, batch, preds, ni):
    """Plot and save model predictions with bounding boxes and keypoints."""
    pred_kpts = torch.cat([p[:, 6:].view(-1, *self.kpt_shape) for p in preds], 0)
    plot_images(
        batch["img"],
        *output_to_target(preds, max_det=self.args.max_det),
        kpts=pred_kpts,
        paths=batch["im_file"],
        fname=self.save_dir / f"val_batch{ni}_pred.jpg",
        names=self.names,
        on_plot=self.on_plot,
    )  # pred

def plot_val_samples(self, batch, ni):
    """Plot and save validation set samples with ground truth bounding boxes and keypoints."""
    plot_images(
        batch["img"],
        batch["batch_idx"],
        batch["cls"].squeeze(-1),
        batch["bboxes"],
        kpts=batch["keypoints"],
        paths=batch["im_file"],
        fname=self.save_dir / f"val_batch{ni}_labels.jpg",
        names=self.names,
        on_plot=self.on_plot,
    )

def pred_to_json(self, predn, filename):
    """Convert YOLO predictions to COCO JSON format."""
    stem = Path(filename).stem
    image_id = int(stem) if stem.isnumeric() else stem
    box = ops.xyxy2xywh(predn[:, :4])  # xywh
    box[:, :2] -= box[:, 2:] / 2  # xy center to top-left corner
    for p, b in zip(predn.tolist(), box.tolist()):
        self.jdict.append(
            {
                "image_id": image_id,
                "category_id": self.class_map[int(p[5])],
                "bbox": [round(x, 3) for x in b],
                "keypoints": p[6:],
                "score": round(p[4], 5),
            }
        )

def preprocess(self, batch):
    """Preprocess batch by converting keypoints data to float and moving it to the device."""
    batch = super().preprocess(batch)
    batch["keypoints"] = batch["keypoints"].to(self.device).float()
    return batch

def save_one_txt(self, predn, pred_kpts, save_conf, shape, file):
    """Save YOLO detections to a txt file in normalized coordinates in a specific format."""
    from ultralytics.engine.results import Results

    Results(
        np.zeros((shape[0], shape[1]), dtype=np.uint8),
        path=None,
        names=self.names,
        boxes=predn[:, :6],
        keypoints=pred_kpts,
    ).save_txt(file, save_conf=save_conf)

def update_metrics(self, preds, batch):
    """
    Update metrics with new predictions and ground truth data.

    This method processes each prediction, compares it with ground truth, and updates various statistics
    for performance evaluation.

    Args:
        preds (List[torch.Tensor]): List of prediction tensors from the model.
        batch (dict): Batch data containing images and ground truth annotations.
    """
    for si, pred in enumerate(preds):
        self.seen += 1
        npr = len(pred)
        stat = dict(
            conf=torch.zeros(0, device=self.device),
            pred_cls=torch.zeros(0, device=self.device),
            tp=torch.zeros(npr, self.niou, dtype=torch.bool, device=self.device),
            tp_p=torch.zeros(npr, self.niou, dtype=torch.bool, device=self.device),
        )
        pbatch = self._prepare_batch(si, batch)
        cls, bbox = pbatch.pop("cls"), pbatch.pop("bbox")
        nl = len(cls)
        stat["target_cls"] = cls
        stat["target_img"] = cls.unique()
        if npr == 0:
            if nl:
                for k in self.stats.keys():
                    self.stats[k].append(stat[k])
                if self.args.plots:
                    self.confusion_matrix.process_batch(detections=None, gt_bboxes=bbox, gt_cls=cls)
            continue

        # Predictions
        if self.args.single_cls:
            pred[:, 5] = 0
        predn, pred_kpts = self._prepare_pred(pred, pbatch)
        stat["conf"] = predn[:, 4]
        stat["pred_cls"] = predn[:, 5]

        # Evaluate
        if nl:
            stat["tp"] = self._process_batch(predn, bbox, cls)
            stat["tp_p"] = self._process_batch(predn, bbox, cls, pred_kpts, pbatch["kpts"])
        if self.args.plots:
            self.confusion_matrix.process_batch(predn, bbox, cls)

        for k in self.stats.keys():
            self.stats[k].append(stat[k])

        # Save
        if self.args.save_json:
            self.pred_to_json(predn, batch["im_file"][si])
        if self.args.save_txt:
            self.save_one_txt(
                predn,
                pred_kpts,
                self.args.save_conf,
                pbatch["ori_shape"],
                self.save_dir / "labels" / f"{Path(batch['im_file'][si]).stem}.txt",
            )