yolo/utils/dataset_utils.py

import json
import os
from itertools import chain
from pathlib import Path
from typing import Any, Dict, List, Optional, Tuple

import numpy as np
import torch

from yolo.tools.data_conversion import discretize_categories
from yolo.utils.logger import logger


def locate_label_paths(dataset_path: Path, phase_name: Path) -> Tuple[Path, Path]:
    """
    Find the path to label files for a specified dataset and phase(e.g. training).

    Args:
        dataset_path (Path): The path to the root directory of the dataset.
        phase_name (Path): The name of the phase for which labels are being searched (e.g., "train", "val", "test").

    Returns:
        Tuple[Path, Path]: A tuple containing the path to the labels file and the file format ("json" or "txt").
    """
    json_labels_path = dataset_path / "annotations" / f"instances_{phase_name}.json"

    txt_labels_path = dataset_path / "labels" / phase_name

    if json_labels_path.is_file():
        return json_labels_path, "json"

    elif txt_labels_path.is_dir():
        txt_files = [f for f in os.listdir(txt_labels_path) if f.endswith(".txt")]
        if txt_files:
            return txt_labels_path, "txt"

    logger.warning("No labels found in the specified dataset path and phase name.")
    return [], None


def create_image_metadata(labels_path: str) -> Tuple[Dict[str, List], Dict[str, Dict]]:
    """
    Create a dictionary containing image information and annotations indexed by image ID.

    Args:
        labels_path (str): The path to the annotation json file.

    Returns:
        - annotations_index: A dictionary where keys are image IDs and values are lists of annotations.
        - image_info_dict: A dictionary where keys are image file names without extension and values are image information dictionaries.
    """
    with open(labels_path, "r") as file:
        labels_data = json.load(file)
        id_to_idx = discretize_categories(labels_data.get("categories", [])) if "categories" in labels_data else None
        annotations_index = organize_annotations_by_image(labels_data, id_to_idx)  # check lookup is a good name?
        image_info_dict = {Path(img["file_name"]).stem: img for img in labels_data["images"]}
        return annotations_index, image_info_dict


def organize_annotations_by_image(data: Dict[str, Any], id_to_idx: Optional[Dict[int, int]]):
    """
    Use image index to lookup every annotations
    Args:
        data (Dict[str, Any]): A dictionary containing annotation data.

    Returns:
        Dict[int, List[Dict[str, Any]]]: A dictionary where keys are image IDs and values are lists of annotations.
        Annotations with "iscrowd" set to True are excluded from the index.

    """
    annotation_lookup = {}
    for anno in data["annotations"]:
        if anno["iscrowd"]:
            continue
        image_id = anno["image_id"]
        if id_to_idx:
            anno["category_id"] = id_to_idx[anno["category_id"]]
        if image_id not in annotation_lookup:
            annotation_lookup[image_id] = []
        annotation_lookup[image_id].append(anno)
    return annotation_lookup


def scale_segmentation(
    annotations: List[Dict[str, Any]], image_dimensions: Dict[str, int]
) -> Optional[List[List[float]]]:
    """
    Scale the segmentation data based on image dimensions and return a list of scaled segmentation data.

    Args:
        annotations (List[Dict[str, Any]]): A list of annotation dictionaries.
        image_dimensions (Dict[str, int]): A dictionary containing image dimensions (height and width).

    Returns:
        Optional[List[List[float]]]: A list of scaled segmentation data, where each sublist contains category_id followed by scaled (x, y) coordinates.
    """
    if annotations is None:
        return None

    seg_array_with_cat = []
    h, w = image_dimensions["height"], image_dimensions["width"]
    for anno in annotations:
        category_id = anno["category_id"]
        if "segmentation" in anno:
            seg_list = [item for sublist in anno["segmentation"] for item in sublist]
        elif "bbox" in anno:
            x, y, width, height = anno["bbox"]
            seg_list = [x, y, x + width, y, x + width, y + height, x, y + height]

        scaled_seg_data = (
            np.array(seg_list).reshape(-1, 2) / [w, h]
        ).tolist()  # make the list group in x, y pairs and scaled with image width, height
        scaled_flat_seg_data = [category_id] + list(chain(*scaled_seg_data))  # flatten the scaled_seg_data list
        seg_array_with_cat.append(scaled_flat_seg_data)

    return seg_array_with_cat


def tensorlize(data):
    try:
        img_paths, bboxes, img_ratios = zip(*data)
    except ValueError as e:
        logger.error(
            ":rotating_light: This may be caused by using old cache or another version of YOLO's cache.\n"
            ":rotating_light: Please clean the cache and try running again."
        )
        raise e
    max_box = max(bbox.size(0) for bbox in bboxes)
    padded_bbox_list = []
    for bbox in bboxes:
        padding = torch.full((max_box, 5), -1, dtype=torch.float32)
        padding[: bbox.size(0)] = bbox
        padded_bbox_list.append(padding)
    bboxes = np.stack(padded_bbox_list)
    img_paths = np.array(img_paths)
    img_ratios = np.array(img_ratios)
    return img_paths, bboxes, img_ratios