pose_classifier.py

# navigation_scripts/pose_classifier.py
import torch
import torch.nn as nn
import torch.nn.functional as F
from torchvision import transforms as T
from pathlib import Path
import numpy as np
from PIL import Image


# Must match train_pose_classifier.py
POSE_CLASSES = ['front', 'front-left', 'front-right', 'left', 'right', 'back-left', 'back-right', 'back']
NUM_CLASSES = len(POSE_CLASSES)

DINO_MODELS = {
    'small': ('dinov2_vits14', 384),
    'base': ('dinov2_vitb14', 768),
    'large': ('dinov2_vitl14', 1024),
}


class _PoseClassifierModel(nn.Module):
    """DINOv2 + MLP head for 8-class pose classification (mirrors train_pose_classifier.PoseClassifier)."""

    def __init__(self, model_size='small', dropout=0.3):
        super().__init__()
        model_name, feat_dim = DINO_MODELS[model_size]

        self.backbone = torch.hub.load('facebookresearch/dinov2', model_name)
        for param in self.backbone.parameters():
            param.requires_grad = False
        self.backbone.eval()

        self.head = nn.Sequential(
            nn.LayerNorm(feat_dim),
            nn.Linear(feat_dim, 256),
            nn.GELU(),
            nn.Dropout(dropout),
            nn.Linear(256, 128),
            nn.GELU(),
            nn.Dropout(dropout),
            nn.Linear(128, NUM_CLASSES),
        )

    def forward(self, x):
        with torch.no_grad():
            features = self.backbone(x)
        return self.head(features)


class ViewPointClassifier:
    """
    Predicts one of 8 canonical zebra viewpoints:
        front, front-left, front-right, left, right, back-left, back-right, back

    Uses a DINOv2-small backbone (frozen) with a trained MLP head.

    __call__(crops) → list[str]
        Each crop is a PIL.Image (RGB).  Returns the predicted pose label.
    """
    LABELS = POSE_CLASSES

    def _to_pil(self, img):
        """Accept PIL.Image | np.ndarray | torch.Tensor -> PIL.Image (RGB)."""
        if isinstance(img, Image.Image):
            return img.convert("RGB")

        if isinstance(img, np.ndarray):
            if img.ndim == 3 and img.shape[2] == 3:
                img = img[..., ::-1]             # BGR → RGB
            return Image.fromarray(img)

        if torch.is_tensor(img):
            return T.ToPILImage()(img.cpu())

        raise TypeError(f"Unsupported crop type {type(img)}")

    def __init__(
        self,
        weight_path="checkpoints/best_pose_model.pth",
        model_size: str = "small",
        device: str = "cpu",
    ):
        self.device = torch.device(device)

        # Build the same architecture used in training
        self.model = _PoseClassifierModel(model_size=model_size)

        # Load checkpoint (saved by train_pose_classifier.py)
        ckpt = torch.load(weight_path, map_location=self.device)
        self.model.load_state_dict(ckpt['model_state_dict'])
        self.model.eval().to(self.device)

        # Match the validation transforms from training
        self.tf = T.Compose(
            [
                T.Resize(256),
                T.CenterCrop(224),
                T.ToTensor(),
                T.Normalize([0.485, 0.456, 0.406], [0.229, 0.224, 0.225]),
            ]
        )

    @torch.inference_mode()
    def __call__(self, crops):
        """
        Parameters
        ----------
        crops : list[PIL.Image]
            One crop per detection.

        Returns
        -------
        list[str]
            Predicted pose label for each crop, e.g. 'front', 'back-left'.
        """
        if not crops:
            return []
        pil_crops = [self._to_pil(c) for c in crops]
        batch = torch.stack([self.tf(c) for c in pil_crops]).to(self.device)
        logits = self.model(batch)                      # shape [N, 8]
        preds = torch.argmax(logits, dim=-1).cpu()      # single-label
        return [self.LABELS[i] for i in preds]

# ───────── quick sanity check ─────────
if __name__ == "__main__":
    from PIL import Image
    import random

    img_dir = Path("some/test/crops")   # directory of zebra chip .jpgs
    samples = [Image.open(p) for p in random.sample(list(img_dir.glob("*.jpg")), 4)]

    clf = ViewPointClassifier(device="cpu")
    print(clf(samples))