detectron2/data/detection_utils.py

# -*- coding: utf-8 -*-
# Copyright (c) Facebook, Inc. and its affiliates.

"""
Common data processing utilities that are used in a
typical object detection data pipeline.
"""
import logging
import numpy as np
from typing import List, Union
import pycocotools.mask as mask_util
import torch
from PIL import Image

from detectron2.structures import (
    BitMasks,
    Boxes,
    BoxMode,
    Instances,
    Keypoints,
    PolygonMasks,
    RotatedBoxes,
    polygons_to_bitmask,
)
from detectron2.utils.file_io import PathManager

from . import transforms as T
from .catalog import MetadataCatalog

__all__ = [
    "SizeMismatchError",
    "convert_image_to_rgb",
    "check_image_size",
    "transform_proposals",
    "transform_instance_annotations",
    "annotations_to_instances",
    "annotations_to_instances_rotated",
    "build_augmentation",
    "build_transform_gen",
    "create_keypoint_hflip_indices",
    "filter_empty_instances",
    "read_image",
]


class SizeMismatchError(ValueError):
    """
    When loaded image has difference width/height compared with annotation.
    """


# https://en.wikipedia.org/wiki/YUV#SDTV_with_BT.601
_M_RGB2YUV = [[0.299, 0.587, 0.114], [-0.14713, -0.28886, 0.436], [0.615, -0.51499, -0.10001]]
_M_YUV2RGB = [[1.0, 0.0, 1.13983], [1.0, -0.39465, -0.58060], [1.0, 2.03211, 0.0]]

# https://www.exiv2.org/tags.html
_EXIF_ORIENT = 274  # exif 'Orientation' tag


def convert_PIL_to_numpy(image, format):
    """
    Convert PIL image to numpy array of target format.

    Args:
        image (PIL.Image): a PIL image
        format (str): the format of output image

    Returns:
        (np.ndarray): also see `read_image`
    """
    if format is not None:
        # PIL only supports RGB, so convert to RGB and flip channels over below
        conversion_format = format
        if format in ["BGR", "YUV-BT.601"]:
            conversion_format = "RGB"
        image = image.convert(conversion_format)
    image = np.asarray(image)
    # PIL squeezes out the channel dimension for "L", so make it HWC
    if format == "L":
        image = np.expand_dims(image, -1)

    # handle formats not supported by PIL
    elif format == "BGR":
        # flip channels if needed
        image = image[:, :, ::-1]
    elif format == "YUV-BT.601":
        image = image / 255.0
        image = np.dot(image, np.array(_M_RGB2YUV).T)

    return image


def convert_image_to_rgb(image, format):
    """
    Convert an image from given format to RGB.

    Args:
        image (np.ndarray or Tensor): an HWC image
        format (str): the format of input image, also see `read_image`

    Returns:
        (np.ndarray): (H,W,3) RGB image in 0-255 range, can be either float or uint8
    """
    if isinstance(image, torch.Tensor):
        image = image.cpu().numpy()
    if format == "BGR":
        image = image[:, :, [2, 1, 0]]
    elif format == "YUV-BT.601":
        image = np.dot(image, np.array(_M_YUV2RGB).T)
        image = image * 255.0
    else:
        if format == "L":
            image = image[:, :, 0]
        image = image.astype(np.uint8)
        image = np.asarray(Image.fromarray(image, mode=format).convert("RGB"))
    return image


def _apply_exif_orientation(image):
    """
    Applies the exif orientation correctly.

    This code exists per the bug:
      https://github.com/python-pillow/Pillow/issues/3973
    with the function `ImageOps.exif_transpose`. The Pillow source raises errors with
    various methods, especially `tobytes`

    Function based on:
      https://github.com/wkentaro/labelme/blob/v4.5.4/labelme/utils/image.py#L59
      https://github.com/python-pillow/Pillow/blob/7.1.2/src/PIL/ImageOps.py#L527

    Args:
        image (PIL.Image): a PIL image

    Returns:
        (PIL.Image): the PIL image with exif orientation applied, if applicable
    """
    if not hasattr(image, "getexif"):
        return image

    try:
        exif = image.getexif()
    except Exception:  # https://github.com/facebookresearch/detectron2/issues/1885
        exif = None

    if exif is None:
        return image

    orientation = exif.get(_EXIF_ORIENT)

    method = {
        2: Image.FLIP_LEFT_RIGHT,
        3: Image.ROTATE_180,
        4: Image.FLIP_TOP_BOTTOM,
        5: Image.TRANSPOSE,
        6: Image.ROTATE_270,
        7: Image.TRANSVERSE,
        8: Image.ROTATE_90,
    }.get(orientation)

    if method is not None:
        return image.transpose(method)
    return image


def read_image(file_name, format=None):
    """
    Read an image into the given format.
    Will apply rotation and flipping if the image has such exif information.

    Args:
        file_name (str): image file path
        format (str): one of the supported image modes in PIL, or "BGR" or "YUV-BT.601".

    Returns:
        image (np.ndarray):
            an HWC image in the given format, which is 0-255, uint8 for
            supported image modes in PIL or "BGR"; float (0-1 for Y) for YUV-BT.601.
    """
    with PathManager.open(file_name, "rb") as f:
        image = Image.open(f)

        # work around this bug: https://github.com/python-pillow/Pillow/issues/3973
        image = _apply_exif_orientation(image)
        return convert_PIL_to_numpy(image, format)


def check_image_size(dataset_dict, image):
    """
    Raise an error if the image does not match the size specified in the dict.
    """
    if "width" in dataset_dict or "height" in dataset_dict:
        image_wh = (image.shape[1], image.shape[0])
        expected_wh = (dataset_dict["width"], dataset_dict["height"])
        if not image_wh == expected_wh:
            raise SizeMismatchError(
                "Mismatched image shape{}, got {}, expect {}.".format(
                    (
                        " for image " + dataset_dict["file_name"]
                        if "file_name" in dataset_dict
                        else ""
                    ),
                    image_wh,
                    expected_wh,
                )
                + " Please check the width/height in your annotation."
            )

    # To ensure bbox always remap to original image size
    if "width" not in dataset_dict:
        dataset_dict["width"] = image.shape[1]
    if "height" not in dataset_dict:
        dataset_dict["height"] = image.shape[0]


def transform_proposals(dataset_dict, image_shape, transforms, *, proposal_topk, min_box_size=0):
    """
    Apply transformations to the proposals in dataset_dict, if any.

    Args:
        dataset_dict (dict): a dict read from the dataset, possibly
            contains fields "proposal_boxes", "proposal_objectness_logits", "proposal_bbox_mode"
        image_shape (tuple): height, width
        transforms (TransformList):
        proposal_topk (int): only keep top-K scoring proposals
        min_box_size (int): proposals with either side smaller than this
            threshold are removed

    The input dict is modified in-place, with abovementioned keys removed. A new
    key "proposals" will be added. Its value is an `Instances`
    object which contains the transformed proposals in its field
    "proposal_boxes" and "objectness_logits".
    """
    if "proposal_boxes" in dataset_dict:
        # Transform proposal boxes
        boxes = transforms.apply_box(
            BoxMode.convert(
                dataset_dict.pop("proposal_boxes"),
                dataset_dict.pop("proposal_bbox_mode"),
                BoxMode.XYXY_ABS,
            )
        )
        boxes = Boxes(boxes)
        objectness_logits = torch.as_tensor(
            dataset_dict.pop("proposal_objectness_logits").astype("float32")
        )

        boxes.clip(image_shape)
        keep = boxes.nonempty(threshold=min_box_size)
        boxes = boxes[keep]
        objectness_logits = objectness_logits[keep]

        proposals = Instances(image_shape)
        proposals.proposal_boxes = boxes[:proposal_topk]
        proposals.objectness_logits = objectness_logits[:proposal_topk]
        dataset_dict["proposals"] = proposals


def get_bbox(annotation):
    """
    Get bbox from data
    Args:
        annotation (dict): dict of instance annotations for a single instance.
    Returns:
        bbox (ndarray): x1, y1, x2, y2 coordinates
    """
    # bbox is 1d (per-instance bounding box)
    bbox = BoxMode.convert(annotation["bbox"], annotation["bbox_mode"], BoxMode.XYXY_ABS)
    return bbox


def transform_instance_annotations(
    annotation, transforms, image_size, *, keypoint_hflip_indices=None
):
    """
    Apply transforms to box, segmentation and keypoints annotations of a single instance.

    It will use `transforms.apply_box` for the box, and
    `transforms.apply_coords` for segmentation polygons & keypoints.
    If you need anything more specially designed for each data structure,
    you'll need to implement your own version of this function or the transforms.

    Args:
        annotation (dict): dict of instance annotations for a single instance.
            It will be modified in-place.
        transforms (TransformList or list[Transform]):
        image_size (tuple): the height, width of the transformed image
        keypoint_hflip_indices (ndarray[int]): see `create_keypoint_hflip_indices`.

    Returns:
        dict:
            the same input dict with fields "bbox", "segmentation", "keypoints"
            transformed according to `transforms`.
            The "bbox_mode" field will be set to XYXY_ABS.
    """
    if isinstance(transforms, (tuple, list)):
        transforms = T.TransformList(transforms)
    # bbox is 1d (per-instance bounding box)
    bbox = BoxMode.convert(annotation["bbox"], annotation["bbox_mode"], BoxMode.XYXY_ABS)
    # clip transformed bbox to image size
    bbox = transforms.apply_box(np.array([bbox]))[0].clip(min=0)
    annotation["bbox"] = np.minimum(bbox, list(image_size + image_size)[::-1])
    annotation["bbox_mode"] = BoxMode.XYXY_ABS

    if "segmentation" in annotation:
        # each instance contains 1 or more polygons
        segm = annotation["segmentation"]
        if isinstance(segm, list):
            # polygons
            polygons = [np.asarray(p).reshape(-1, 2) for p in segm]
            annotation["segmentation"] = [
                p.reshape(-1) for p in transforms.apply_polygons(polygons)
            ]
        elif isinstance(segm, dict):
            # RLE
            mask = mask_util.decode(segm)
            mask = transforms.apply_segmentation(mask)
            assert tuple(mask.shape[:2]) == image_size
            annotation["segmentation"] = mask
        else:
            raise ValueError(
                "Cannot transform segmentation of type '{}'!"
                "Supported types are: polygons as list[list[float] or ndarray],"
                " COCO-style RLE as a dict.".format(type(segm))
            )

    if "keypoints" in annotation:
        keypoints = transform_keypoint_annotations(
            annotation["keypoints"], transforms, image_size, keypoint_hflip_indices
        )
        annotation["keypoints"] = keypoints

    return annotation


def transform_keypoint_annotations(keypoints, transforms, image_size, keypoint_hflip_indices=None):
    """
    Transform keypoint annotations of an image.
    If a keypoint is transformed out of image boundary, it will be marked "unlabeled" (visibility=0)

    Args:
        keypoints (list[float]): Nx3 float in Detectron2's Dataset format.
            Each point is represented by (x, y, visibility).
        transforms (TransformList):
        image_size (tuple): the height, width of the transformed image
        keypoint_hflip_indices (ndarray[int]): see `create_keypoint_hflip_indices`.
            When `transforms` includes horizontal flip, will use the index
            mapping to flip keypoints.
    """
    # (N*3,) -> (N, 3)
    keypoints = np.asarray(keypoints, dtype="float64").reshape(-1, 3)
    keypoints_xy = transforms.apply_coords(keypoints[:, :2])

    # Set all out-of-boundary points to "unlabeled"
    inside = (keypoints_xy >= np.array([0, 0])) & (keypoints_xy <= np.array(image_size[::-1]))
    inside = inside.all(axis=1)
    keypoints[:, :2] = keypoints_xy
    keypoints[:, 2][~inside] = 0

    # This assumes that HorizFlipTransform is the only one that does flip
    do_hflip = sum(isinstance(t, T.HFlipTransform) for t in transforms.transforms) % 2 == 1

    # Alternative way: check if probe points was horizontally flipped.
    # probe = np.asarray([[0.0, 0.0], [image_width, 0.0]])
    # probe_aug = transforms.apply_coords(probe.copy())
    # do_hflip = np.sign(probe[1][0] - probe[0][0]) != np.sign(probe_aug[1][0] - probe_aug[0][0])  # noqa

    # If flipped, swap each keypoint with its opposite-handed equivalent
    if do_hflip:
        if keypoint_hflip_indices is None:
            raise ValueError("Cannot flip keypoints without providing flip indices!")
        if len(keypoints) != len(keypoint_hflip_indices):
            raise ValueError(
                "Keypoint data has {} points, but metadata "
                "contains {} points!".format(len(keypoints), len(keypoint_hflip_indices))
            )
        keypoints = keypoints[np.asarray(keypoint_hflip_indices, dtype=np.int32), :]

    # Maintain COCO convention that if visibility == 0 (unlabeled), then x, y = 0
    keypoints[keypoints[:, 2] == 0] = 0
    return keypoints


def annotations_to_instances(annos, image_size, mask_format="polygon"):
    """
    Create an :class:`Instances` object used by the models,
    from instance annotations in the dataset dict.

    Args:
        annos (list[dict]): a list of instance annotations in one image, each
            element for one instance.
        image_size (tuple): height, width

    Returns:
        Instances:
            It will contain fields "gt_boxes", "gt_classes",
            "gt_masks", "gt_keypoints", if they can be obtained from `annos`.
            This is the format that builtin models expect.
    """
    boxes = (
        np.stack(
            [BoxMode.convert(obj["bbox"], obj["bbox_mode"], BoxMode.XYXY_ABS) for obj in annos]
        )
        if len(annos)
        else np.zeros((0, 4))
    )
    target = Instances(image_size)
    target.gt_boxes = Boxes(boxes)

    classes = [int(obj["category_id"]) for obj in annos]
    classes = torch.tensor(classes, dtype=torch.int64)
    target.gt_classes = classes

    if len(annos) and "segmentation" in annos[0]:
        segms = [obj["segmentation"] for obj in annos]
        if mask_format == "polygon":
            try:
                masks = PolygonMasks(segms)
            except ValueError as e:
                raise ValueError(
                    "Failed to use mask_format=='polygon' from the given annotations!"
                ) from e
        else:
            assert mask_format == "bitmask", mask_format
            masks = []
            for segm in segms:
                if isinstance(segm, list):
                    # polygon
                    masks.append(polygons_to_bitmask(segm, *image_size))
                elif isinstance(segm, dict):
                    # COCO RLE
                    masks.append(mask_util.decode(segm))
                elif isinstance(segm, np.ndarray):
                    assert segm.ndim == 2, "Expect segmentation of 2 dimensions, got {}.".format(
                        segm.ndim
                    )
                    # mask array
                    masks.append(segm)
                else:
                    raise ValueError(
                        "Cannot convert segmentation of type '{}' to BitMasks!"
                        "Supported types are: polygons as list[list[float] or ndarray],"
                        " COCO-style RLE as a dict, or a binary segmentation mask "
                        " in a 2D numpy array of shape HxW.".format(type(segm))
                    )
            # torch.from_numpy does not support array with negative stride.
            masks = BitMasks(
                torch.stack([torch.from_numpy(np.ascontiguousarray(x)) for x in masks])
            )
        target.gt_masks = masks

    if len(annos) and "keypoints" in annos[0]:
        kpts = [obj.get("keypoints", []) for obj in annos]
        target.gt_keypoints = Keypoints(kpts)

    return target


def annotations_to_instances_rotated(annos, image_size):
    """
    Create an :class:`Instances` object used by the models,
    from instance annotations in the dataset dict.
    Compared to `annotations_to_instances`, this function is for rotated boxes only

    Args:
        annos (list[dict]): a list of instance annotations in one image, each
            element for one instance.
        image_size (tuple): height, width

    Returns:
        Instances:
            Containing fields "gt_boxes", "gt_classes",
            if they can be obtained from `annos`.
            This is the format that builtin models expect.
    """
    boxes = [obj["bbox"] for obj in annos]
    target = Instances(image_size)
    boxes = target.gt_boxes = RotatedBoxes(boxes)
    boxes.clip(image_size)

    classes = [obj["category_id"] for obj in annos]
    classes = torch.tensor(classes, dtype=torch.int64)
    target.gt_classes = classes

    return target


def filter_empty_instances(
    instances, by_box=True, by_mask=True, box_threshold=1e-5, return_mask=False
):
    """
    Filter out empty instances in an `Instances` object.

    Args:
        instances (Instances):
        by_box (bool): whether to filter out instances with empty boxes
        by_mask (bool): whether to filter out instances with empty masks
        box_threshold (float): minimum width and height to be considered non-empty
        return_mask (bool): whether to return boolean mask of filtered instances

    Returns:
        Instances: the filtered instances.
        tensor[bool], optional: boolean mask of filtered instances
    """
    assert by_box or by_mask
    r = []
    if by_box:
        r.append(instances.gt_boxes.nonempty(threshold=box_threshold))
    if instances.has("gt_masks") and by_mask:
        r.append(instances.gt_masks.nonempty())

    # TODO: can also filter visible keypoints

    if not r:
        return instances
    m = r[0]
    for x in r[1:]:
        m = m & x
    if return_mask:
        return instances[m], m
    return instances[m]


def create_keypoint_hflip_indices(dataset_names: Union[str, List[str]]) -> List[int]:
    """
    Args:
        dataset_names: list of dataset names

    Returns:
        list[int]: a list of size=#keypoints, storing the
        horizontally-flipped keypoint indices.
    """
    if isinstance(dataset_names, str):
        dataset_names = [dataset_names]

    check_metadata_consistency("keypoint_names", dataset_names)
    check_metadata_consistency("keypoint_flip_map", dataset_names)

    meta = MetadataCatalog.get(dataset_names[0])
    names = meta.keypoint_names
    # TODO flip -> hflip
    flip_map = dict(meta.keypoint_flip_map)
    flip_map.update({v: k for k, v in flip_map.items()})
    flipped_names = [i if i not in flip_map else flip_map[i] for i in names]
    flip_indices = [names.index(i) for i in flipped_names]
    return flip_indices


def get_fed_loss_cls_weights(dataset_names: Union[str, List[str]], freq_weight_power=1.0):
    """
    Get frequency weight for each class sorted by class id.
    We now calcualte freqency weight using image_count to the power freq_weight_power.

    Args:
        dataset_names: list of dataset names
        freq_weight_power: power value
    """
    if isinstance(dataset_names, str):
        dataset_names = [dataset_names]

    check_metadata_consistency("class_image_count", dataset_names)

    meta = MetadataCatalog.get(dataset_names[0])
    class_freq_meta = meta.class_image_count
    class_freq = torch.tensor(
        [c["image_count"] for c in sorted(class_freq_meta, key=lambda x: x["id"])]
    )
    class_freq_weight = class_freq.float() ** freq_weight_power
    return class_freq_weight


def gen_crop_transform_with_instance(crop_size, image_size, instance):
    """
    Generate a CropTransform so that the cropping region contains
    the center of the given instance.

    Args:
        crop_size (tuple): h, w in pixels
        image_size (tuple): h, w
        instance (dict): an annotation dict of one instance, in Detectron2's
            dataset format.
    """
    crop_size = np.asarray(crop_size, dtype=np.int32)
    bbox = BoxMode.convert(instance["bbox"], instance["bbox_mode"], BoxMode.XYXY_ABS)
    center_yx = (bbox[1] + bbox[3]) * 0.5, (bbox[0] + bbox[2]) * 0.5
    assert (
        image_size[0] >= center_yx[0] and image_size[1] >= center_yx[1]
    ), "The annotation bounding box is outside of the image!"
    assert (
        image_size[0] >= crop_size[0] and image_size[1] >= crop_size[1]
    ), "Crop size is larger than image size!"

    min_yx = np.maximum(np.floor(center_yx).astype(np.int32) - crop_size, 0)
    max_yx = np.maximum(np.asarray(image_size, dtype=np.int32) - crop_size, 0)
    max_yx = np.minimum(max_yx, np.ceil(center_yx).astype(np.int32))

    y0 = np.random.randint(min_yx[0], max_yx[0] + 1)
    x0 = np.random.randint(min_yx[1], max_yx[1] + 1)
    return T.CropTransform(x0, y0, crop_size[1], crop_size[0])


def check_metadata_consistency(key, dataset_names):
    """
    Check that the datasets have consistent metadata.

    Args:
        key (str): a metadata key
        dataset_names (list[str]): a list of dataset names

    Raises:
        AttributeError: if the key does not exist in the metadata
        ValueError: if the given datasets do not have the same metadata values defined by key
    """
    if len(dataset_names) == 0:
        return
    logger = logging.getLogger(__name__)
    entries_per_dataset = [getattr(MetadataCatalog.get(d), key) for d in dataset_names]
    for idx, entry in enumerate(entries_per_dataset):
        if entry != entries_per_dataset[0]:
            logger.error(
                "Metadata '{}' for dataset '{}' is '{}'".format(key, dataset_names[idx], str(entry))
            )
            logger.error(
                "Metadata '{}' for dataset '{}' is '{}'".format(
                    key, dataset_names[0], str(entries_per_dataset[0])
                )
            )
            raise ValueError("Datasets have different metadata '{}'!".format(key))


def build_augmentation(cfg, is_train):
    """
    Create a list of default :class:`Augmentation` from config.
    Now it includes resizing and flipping.

    Returns:
        list[Augmentation]
    """
    if is_train:
        min_size = cfg.INPUT.MIN_SIZE_TRAIN
        max_size = cfg.INPUT.MAX_SIZE_TRAIN
        sample_style = cfg.INPUT.MIN_SIZE_TRAIN_SAMPLING
    else:
        min_size = cfg.INPUT.MIN_SIZE_TEST
        max_size = cfg.INPUT.MAX_SIZE_TEST
        sample_style = "choice"
    augmentation = [T.ResizeShortestEdge(min_size, max_size, sample_style)]
    if is_train and cfg.INPUT.RANDOM_FLIP != "none":
        augmentation.append(
            T.RandomFlip(
                horizontal=cfg.INPUT.RANDOM_FLIP == "horizontal",
                vertical=cfg.INPUT.RANDOM_FLIP == "vertical",
            )
        )
    return augmentation


build_transform_gen = build_augmentation
"""
Alias for backward-compatibility.
"""