src/python-doctr/doctr/datasets/svhn.py

# Copyright (C) 2021-2025, Mindee.

# This program is licensed under the Apache License 2.0.
# See LICENSE or go to <https://opensource.org/licenses/Apache-2.0> for full license details.

import os
from typing import Any

import h5py
import numpy as np
from tqdm import tqdm

from .datasets import VisionDataset
from .utils import convert_target_to_relative, crop_bboxes_from_image

__all__ = ["SVHN"]


class SVHN(VisionDataset):
    """SVHN dataset from `"The Street View House Numbers (SVHN) Dataset"
    <http://ufldl.stanford.edu/housenumbers/>`_.

    .. image:: https://doctr-static.mindee.com/models?id=v0.5.0/svhn-grid.png&src=0
        :align: center

    >>> from doctr.datasets import SVHN
    >>> train_set = SVHN(train=True, download=True)
    >>> img, target = train_set[0]

    Args:
        train: whether the subset should be the training one
        use_polygons: whether polygons should be considered as rotated bounding box (instead of straight ones)
        recognition_task: whether the dataset should be used for recognition task
        detection_task: whether the dataset should be used for detection task
        **kwargs: keyword arguments from `VisionDataset`.
    """

    TRAIN = (
        "http://ufldl.stanford.edu/housenumbers/train.tar.gz",
        "4b17bb33b6cd8f963493168f80143da956f28ec406cc12f8e5745a9f91a51898",
        "svhn_train.tar",
    )

    TEST = (
        "http://ufldl.stanford.edu/housenumbers/test.tar.gz",
        "57ac9ceb530e4aa85b55d991be8fc49c695b3d71c6f6a88afea86549efde7fb5",
        "svhn_test.tar",
    )

    def __init__(
        self,
        train: bool = True,
        use_polygons: bool = False,
        recognition_task: bool = False,
        detection_task: bool = False,
        **kwargs: Any,
    ) -> None:
        url, sha256, name = self.TRAIN if train else self.TEST
        super().__init__(
            url,
            file_name=name,
            file_hash=sha256,
            extract_archive=True,
            pre_transforms=convert_target_to_relative if not recognition_task else None,
            **kwargs,
        )
        if recognition_task and detection_task:
            raise ValueError(
                "`recognition_task` and `detection_task` cannot be set to True simultaneously. "
                + "To get the whole dataset with boxes and labels leave both parameters to False."
            )

        self.train = train
        self.data: list[tuple[str | np.ndarray, str | dict[str, Any] | np.ndarray]] = []
        np_dtype = np.float32

        tmp_root = os.path.join(self.root, "train" if train else "test")

        # Load mat data (matlab v7.3 - can not be loaded with scipy)
        with h5py.File(os.path.join(tmp_root, "digitStruct.mat"), "r") as f:
            img_refs = f["digitStruct/name"]
            box_refs = f["digitStruct/bbox"]
            for img_ref, box_ref in tqdm(
                iterable=zip(img_refs, box_refs), desc="Preparing and Loading SVHN", total=len(img_refs)
            ):
                # convert ascii matrix to string
                img_name = "".join(map(chr, f[img_ref[0]][()].flatten()))

                # File existence check
                if not os.path.exists(os.path.join(tmp_root, img_name)):
                    raise FileNotFoundError(f"unable to locate {os.path.join(tmp_root, img_name)}")

                # Unpack the information
                box = f[box_ref[0]]
                if box["left"].shape[0] == 1:
                    box_dict = {k: [int(vals[0][0])] for k, vals in box.items()}
                else:
                    box_dict = {k: [int(f[v[0]][()].item()) for v in vals] for k, vals in box.items()}

                # Convert it to the right format
                coords: np.ndarray = np.array(
                    [box_dict["left"], box_dict["top"], box_dict["width"], box_dict["height"]], dtype=np_dtype
                ).transpose()
                label_targets = list(map(str, box_dict["label"]))

                if use_polygons:
                    # (x, y) coordinates of top left, top right, bottom right, bottom left corners
                    box_targets: np.ndarray = np.stack(
                        [
                            np.stack([coords[:, 0], coords[:, 1]], axis=-1),
                            np.stack([coords[:, 0] + coords[:, 2], coords[:, 1]], axis=-1),
                            np.stack([coords[:, 0] + coords[:, 2], coords[:, 1] + coords[:, 3]], axis=-1),
                            np.stack([coords[:, 0], coords[:, 1] + coords[:, 3]], axis=-1),
                        ],
                        axis=1,
                    )
                else:
                    # x, y, width, height -> xmin, ymin, xmax, ymax
                    box_targets = np.stack(
                        [
                            coords[:, 0],
                            coords[:, 1],
                            coords[:, 0] + coords[:, 2],
                            coords[:, 1] + coords[:, 3],
                        ],
                        axis=-1,
                    )

                if recognition_task:
                    crops = crop_bboxes_from_image(img_path=os.path.join(tmp_root, img_name), geoms=box_targets)
                    for crop, label in zip(crops, label_targets):
                        if crop.shape[0] > 0 and crop.shape[1] > 0 and len(label) > 0 and " " not in label:
                            self.data.append((crop, label))
                elif detection_task:
                    self.data.append((img_name, box_targets))
                else:
                    self.data.append((img_name, dict(boxes=box_targets, labels=label_targets)))

        self.root = tmp_root

    def extra_repr(self) -> str:
        return f"train={self.train}"