utils/box_utils.py

# utils/box_utils.py
import numpy as np
from scipy.interpolate import interp1d

def interpolate_boxes(
    keyboxes: dict,    # {frame_idx: [x1, y1, x2, y2]}
    num_frames: int,
    method: str = "linear"  # "linear" or "cubic"
) -> np.ndarray:
    """
    Interpolate sparse keyboxes to dense per-frame boxes.
    Returns: [T, 4] float32
    """
    frame_ids = sorted(keyboxes.keys())
    boxes = np.array([keyboxes[i] for i in frame_ids], dtype=np.float32)

    # Interpolate each coordinate separately
    result = np.zeros((num_frames, 4), dtype=np.float32)
    t_query = np.arange(num_frames)

    for coord in range(4):
        f = interp1d(
            frame_ids,
            boxes[:, coord],
            kind=method,
            fill_value="extrapolate"
        )
        result[:, coord] = f(t_query)

    return result.clip(0, None)  # boxes can't be negative

def box_to_mask(
    box: np.ndarray,  # [x1, y1, x2, y2]
    H: int,
    W: int
) -> np.ndarray:
    """
    Convert bounding box to binary mask [H, W]
    """
    mask = np.zeros((H, W), dtype=np.float32)
    x1, y1, x2, y2 = box.astype(int)
    x1, x2 = np.clip([x1, x2], 0, W)
    y1, y2 = np.clip([y1, y2], 0, H)
    mask[y1:y2, x1:x2] = 1.0
    return mask

def boxes_to_mask_sequence(
    boxes: np.ndarray,  # [T, 4]
    H: int,
    W: int
) -> np.ndarray:
    """
    Returns: [T, H, W] binary masks
    """
    T = len(boxes)
    masks = np.zeros((T, H, W), dtype=np.float32)
    for t, box in enumerate(boxes):
        masks[t] = box_to_mask(box, H, W)
    return masks

def expand_box(box: np.ndarray, padding: int = 10) -> np.ndarray:
    """Expand box by padding pixels on each side"""
    x1, y1, x2, y2 = box
    return np.array([x1 - padding, y1 - padding,
                     x2 + padding, y2 + padding])