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# Copyright (c) Open-CD. All rights reserved.
import copy
import warnings
from typing import Dict, Iterable, List, Optional, Sequence, Tuple, Union

import cv2
import mmcv
import numpy as np
from mmcv.image.geometric import _scale_size
from mmcv.transforms.base import BaseTransform
from mmcv.transforms.utils import cache_randomness
from mmengine.utils import is_list_of, is_seq_of, is_str, is_tuple_of
from numpy import random
from scipy.ndimage import gaussian_filter

from mmseg.datasets.dataset_wrappers import MultiImageMixDataset
from opencd.registry import TRANSFORMS

try:
    import albumentations
    from albumentations import Compose
except ImportError:
    albumentations = None
    Compose = None


@TRANSFORMS.register_module()
class MultiImgResizeToMultiple(BaseTransform):
    """Resize images & seg to multiple of divisor.

    Required Keys:

    - img
    - gt_seg_map

    Modified Keys:

    - img
    - img_shape
    - pad_shape

    Args:
        size_divisor (int): images and gt seg maps need to resize to multiple
            of size_divisor. Default: 32.
        interpolation (str, optional): The interpolation mode of image resize.
            Default: None
    """

    def __init__(self, size_divisor=32, interpolation=None):
        self.size_divisor = size_divisor
        self.interpolation = interpolation

    def transform(self, results: dict) -> dict:
        """Call function to resize images, semantic segmentation map to
        multiple of size divisor.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            dict: Resized results, 'img_shape', 'pad_shape' keys are updated.
        """
        # Align image to multiple of size divisor.
        imgs = results['img']
        imgs = [
            mmcv.imresize_to_multiple(
                    img,
                    self.size_divisor,
                    scale_factor=1,
                    interpolation=self.interpolation
                    if self.interpolation else 'bilinear') for img in imgs]

        results['img'] = imgs
        results['img_shape'] = imgs[0].shape
        results['pad_shape'] = imgs[0].shape

        # Align segmentation map to multiple of size divisor.
        for key in results.get('seg_fields', []):
            gt_seg = results[key]
            gt_seg = mmcv.imresize_to_multiple(
                gt_seg,
                self.size_divisor,
                scale_factor=1,
                interpolation='nearest')
            results[key] = gt_seg

        return results

    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += (f'(size_divisor={self.size_divisor}, '
                     f'interpolation={self.interpolation})')
        return repr_str


@TRANSFORMS.register_module()
class MultiImgRerange(BaseTransform):
    """Rerange the image pixel value.

    Required Keys:

    - img

    Modified Keys:

    - img

    Args:
        min_value (float or int): Minimum value of the reranged image.
            Default: 0.
        max_value (float or int): Maximum value of the reranged image.
            Default: 255.
    """

    def __init__(self, min_value=0, max_value=255):
        assert isinstance(min_value, float) or isinstance(min_value, int)
        assert isinstance(max_value, float) or isinstance(max_value, int)
        assert min_value < max_value
        self.min_value = min_value
        self.max_value = max_value

    def transform(self, results: dict) -> dict:
        """Call function to rerange images.

        Args:
            results (dict): Result dict from loading pipeline.
        Returns:
            dict: Reranged results.
        """

        def _rerange(img):
            img_min_value = np.min(img)
            img_max_value = np.max(img)

            assert img_min_value < img_max_value
            # rerange to [0, 1]
            img = (img - img_min_value) / (img_max_value - img_min_value)
            # rerange to [min_value, max_value]
            img = img * (self.max_value - self.min_value) + self.min_value
            return img

        results['img'] = [_rerange(img) for img in results['img']]

        return results

    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += f'(min_value={self.min_value}, max_value={self.max_value})'
        return repr_str


@TRANSFORMS.register_module()
class MultiImgCLAHE(BaseTransform):
    """Use CLAHE method to process the image.

    See `ZUIDERVELD,K. Contrast Limited Adaptive Histogram Equalization[J].
    Graphics Gems, 1994:474-485.` for more information.

    Required Keys:

    - img

    Modified Keys:

    - img

    Args:
        clip_limit (float): Threshold for contrast limiting. Default: 40.0.
        tile_grid_size (tuple[int]): Size of grid for histogram equalization.
            Input image will be divided into equally sized rectangular tiles.
            It defines the number of tiles in row and column. Default: (8, 8).
    """

    def __init__(self, clip_limit=40.0, tile_grid_size=(8, 8)):
        assert isinstance(clip_limit, (float, int))
        self.clip_limit = clip_limit
        assert is_tuple_of(tile_grid_size, int)
        assert len(tile_grid_size) == 2
        self.tile_grid_size = tile_grid_size

    def transform(self, results: dict) -> dict:
        """Call function to Use CLAHE method process images.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            dict: Processed results.
        """
        
        def _clane(img):
            for i in range(img.shape[2]):
                img[:, :, i] = mmcv.clahe(
                    np.array(img[:, :, i], dtype=np.uint8),
                    self.clip_limit, self.tile_grid_size)
            return img

        results['img'] = [_clane(img) for img in results['img']]

        return results

    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += f'(clip_limit={self.clip_limit}, '\
                    f'tile_grid_size={self.tile_grid_size})'
        return repr_str


@TRANSFORMS.register_module()
class MultiImgRandomCrop(BaseTransform):
    """Random crop the image & seg.

    Required Keys:

    - img
    - gt_seg_map

    Modified Keys:

    - img
    - img_shape
    - gt_seg_map


    Args:
        crop_size (Union[int, Tuple[int, int]]):  Expected size after cropping
            with the format of (h, w). If set to an integer, then cropping
            width and height are equal to this integer.
        cat_max_ratio (float): The maximum ratio that single category could
            occupy.
        ignore_index (int): The label index to be ignored. Default: 255
    """

    def __init__(self,
                 crop_size: Union[int, Tuple[int, int]],
                 cat_max_ratio: float = 1.,
                 ignore_index: int = 255):
        super().__init__()
        assert isinstance(crop_size, int) or (
            isinstance(crop_size, tuple) and len(crop_size) == 2
        ), 'The expected crop_size is an integer, or a tuple containing two '
        'intergers'

        if isinstance(crop_size, int):
            crop_size = (crop_size, crop_size)
        assert crop_size[0] > 0 and crop_size[1] > 0
        self.crop_size = crop_size
        self.cat_max_ratio = cat_max_ratio
        self.ignore_index = ignore_index

    @cache_randomness
    def crop_bbox(self, results: dict) -> tuple:
        """get a crop bounding box.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            tuple: Coordinates of the cropped image.
        """

        def generate_crop_bbox(img: np.ndarray) -> tuple:
            """Randomly get a crop bounding box.

            Args:
                img (np.ndarray): Original input image.

            Returns:
                tuple: Coordinates of the cropped image.
            """

            margin_h = max(img.shape[0] - self.crop_size[0], 0)
            margin_w = max(img.shape[1] - self.crop_size[1], 0)
            offset_h = np.random.randint(0, margin_h + 1)
            offset_w = np.random.randint(0, margin_w + 1)
            crop_y1, crop_y2 = offset_h, offset_h + self.crop_size[0]
            crop_x1, crop_x2 = offset_w, offset_w + self.crop_size[1]

            return crop_y1, crop_y2, crop_x1, crop_x2

        img = results['img'][0]
        crop_bbox = generate_crop_bbox(img)
        if self.cat_max_ratio < 1.:
            # Repeat 10 times
            for _ in range(10):
                seg_temp = self.crop(results['gt_seg_map'], crop_bbox)
                labels, cnt = np.unique(seg_temp, return_counts=True)
                cnt = cnt[labels != self.ignore_index]
                if len(cnt) > 1 and np.max(cnt) / np.sum(
                        cnt) < self.cat_max_ratio:
                    break
                crop_bbox = generate_crop_bbox(img)

        return crop_bbox

    def crop(self, img: np.ndarray, crop_bbox: tuple) -> np.ndarray:
        """Crop from ``img``

        Args:
            img (np.ndarray): Original input image.
            crop_bbox (tuple): Coordinates of the cropped image.

        Returns:
            np.ndarray: The cropped image.
        """

        crop_y1, crop_y2, crop_x1, crop_x2 = crop_bbox
        img = img[crop_y1:crop_y2, crop_x1:crop_x2, ...]
        return img

    def transform(self, results: dict) -> dict:
        """Transform function to randomly crop images, semantic segmentation
        maps.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            dict: Randomly cropped results, 'img_shape' key in result dict is
                updated according to crop size.
        """

        crop_bbox = self.crop_bbox(results)

        # crop the image
        imgs = [self.crop(img, crop_bbox) for img in results['img']]

        # crop semantic seg
        for key in results.get('seg_fields', []):
            results[key] = self.crop(results[key], crop_bbox)

        results['img'] = imgs
        results['img_shape'] = imgs[0].shape
        return results

    def __repr__(self):
        return self.__class__.__name__ + f'(crop_size={self.crop_size})'


@TRANSFORMS.register_module()
class MultiImgRandomRotate(BaseTransform):
    """Rotate the image & seg.

    Required Keys:

    - img
    - gt_seg_map

    Modified Keys:

    - img
    - gt_seg_map

    Args:
        prob (float): The rotation probability.
        degree (float, tuple[float]): Range of degrees to select from. If
            degree is a number instead of tuple like (min, max),
            the range of degree will be (``-degree``, ``+degree``)
        pad_val (float, optional): Padding value of image. Default: 0.
        seg_pad_val (float, optional): Padding value of segmentation map.
            Default: 255.
        center (tuple[float], optional): Center point (w, h) of the rotation in
            the source image. If not specified, the center of the image will be
            used. Default: None.
        auto_bound (bool): Whether to adjust the image size to cover the whole
            rotated image. Default: False
    """

    def __init__(self,
                 prob,
                 degree,
                 pad_val=0,
                 seg_pad_val=255,
                 center=None,
                 auto_bound=False):
        self.prob = prob
        assert prob >= 0 and prob <= 1
        if isinstance(degree, (float, int)):
            assert degree > 0, f'degree {degree} should be positive'
            self.degree = (-degree, degree)
        else:
            self.degree = degree
        assert len(self.degree) == 2, f'degree {self.degree} should be a ' \
                                      f'tuple of (min, max)'
        self.pal_val = pad_val
        self.seg_pad_val = seg_pad_val
        self.center = center
        self.auto_bound = auto_bound

    @cache_randomness
    def generate_degree(self):
        return np.random.rand() < self.prob, np.random.uniform(
            min(*self.degree), max(*self.degree))

    def transform(self, results: dict) -> dict:
        """Call function to rotate image, semantic segmentation maps.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            dict: Rotated results.
        """

        rotate, degree = self.generate_degree()
        if rotate:
            # rotate image
            results['img'] = [
                mmcv.imrotate(
                    img,
                    angle=degree,
                    border_value=self.pal_val,
                    center=self.center,
                    auto_bound=self.auto_bound) for img in results['img']]

            # rotate segs
            for key in results.get('seg_fields', []):
                results[key] = mmcv.imrotate(
                    results[key],
                    angle=degree,
                    border_value=self.seg_pad_val,
                    center=self.center,
                    auto_bound=self.auto_bound,
                    interpolation='nearest')
        return results

    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += f'(prob={self.prob}, ' \
                    f'degree={self.degree}, ' \
                    f'pad_val={self.pal_val}, ' \
                    f'seg_pad_val={self.seg_pad_val}, ' \
                    f'center={self.center}, ' \
                    f'auto_bound={self.auto_bound})'
        return repr_str


@TRANSFORMS.register_module()
class MultiImgRGB2Gray(BaseTransform):
    """Convert RGB image to grayscale image.

    Required Keys:

    - img

    Modified Keys:

    - img
    - img_shape

    This transform calculate the weighted mean of input image channels with
    ``weights`` and then expand the channels to ``out_channels``. When
    ``out_channels`` is None, the number of output channels is the same as
    input channels.

    Args:
        out_channels (int): Expected number of output channels after
            transforming. Default: None.
        weights (tuple[float]): The weights to calculate the weighted mean.
            Default: (0.299, 0.587, 0.114).
    """

    def __init__(self, out_channels=None, weights=(0.299, 0.587, 0.114)):
        assert out_channels is None or out_channels > 0
        self.out_channels = out_channels
        assert isinstance(weights, tuple)
        for item in weights:
            assert isinstance(item, (float, int))
        self.weights = weights

    def transform(self, results: dict) -> dict:
        """Call function to convert RGB image to grayscale image.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            dict: Result dict with grayscale image.
        """

        def _rgb2gray(img):
            assert len(img.shape) == 3
            assert img.shape[2] == len(self.weights)
            weights = np.array(self.weights).reshape((1, 1, -1))
            img = (img * weights).sum(2, keepdims=True)
            if self.out_channels is None:
                img = img.repeat(weights.shape[2], axis=2)
            else:
                img = img.repeat(self.out_channels, axis=2)
            return img

        imgs = [_rgb2gray(img) for img in results['img']]

        results['img'] = imgs
        results['img_shape'] = imgs[0].shape

        return results

    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += f'(out_channels={self.out_channels}, ' \
                    f'weights={self.weights})'
        return repr_str


@TRANSFORMS.register_module()
class MultiImgAdjustGamma(BaseTransform):
    """Using gamma correction to process the image.

    Required Keys:

    - img

    Modified Keys:

    - img

    Args:
        gamma (float or int): Gamma value used in gamma correction.
            Default: 1.0.
    """

    def __init__(self, gamma=1.0):
        assert isinstance(gamma, float) or isinstance(gamma, int)
        assert gamma > 0
        self.gamma = gamma
        inv_gamma = 1.0 / gamma
        self.table = np.array([(i / 255.0)**inv_gamma * 255
                               for i in np.arange(256)]).astype('uint8')

    def transform(self, results: dict) -> dict:
        """Call function to process the image with gamma correction.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            dict: Processed results.
        """

        results['img'] = [
            mmcv.lut_transform(
                np.array(img, dtype=np.uint8), self.table) for img in results['img']
        ]

        return results

    def __repr__(self):
        return self.__class__.__name__ + f'(gamma={self.gamma})'


@TRANSFORMS.register_module()
class MultiImgPhotoMetricDistortion(BaseTransform):
    """Apply photometric distortion to image sequentially, every transformation
    is applied with a probability of 0.5. The position of random contrast is in
    second or second to last.

    1. random brightness
    2. random contrast (mode 0)
    3. convert color from BGR to HSV
    4. random saturation
    5. random hue
    6. convert color from HSV to BGR
    7. random contrast (mode 1)

    Required Keys:

    - img

    Modified Keys:

    - img

    Args:
        brightness_delta (int): delta of brightness.
        contrast_range (tuple): range of contrast.
        saturation_range (tuple): range of saturation.
        hue_delta (int): delta of hue.
        consistent_contrast_mode (bool): Whether to 
        keep the contrast mode consistent.
    """

    def __init__(self,
                 brightness_delta: int = 32,
                 contrast_range: Sequence[float] = (0.5, 1.5),
                 saturation_range: Sequence[float] = (0.5, 1.5),
                 hue_delta: int = 18,
                 consistent_contrast_mode: bool = False):
        self.brightness_delta = brightness_delta
        self.contrast_lower, self.contrast_upper = contrast_range
        self.saturation_lower, self.saturation_upper = saturation_range
        self.hue_delta = hue_delta
        self.consistent_contrast_mode = consistent_contrast_mode

    def convert(self,
                img: np.ndarray,
                alpha: int = 1,
                beta: int = 0) -> np.ndarray:
        """Multiple with alpha and add beat with clip.

        Args:
            img (np.ndarray): The input image.
            alpha (int): Image weights, change the contrast/saturation
                of the image. Default: 1
            beta (int): Image bias, change the brightness of the
                image. Default: 0

        Returns:
            np.ndarray: The transformed image.
        """

        img = img.astype(np.float32) * alpha + beta
        img = np.clip(img, 0, 255)
        return img.astype(np.uint8)

    def brightness(self, img: np.ndarray) -> np.ndarray:
        """Brightness distortion.

        Args:
            img (np.ndarray): The input image.
        Returns:
            np.ndarray: Image after brightness change.
        """

        if random.randint(2):
            return self.convert(
                img,
                beta=random.uniform(-self.brightness_delta,
                                    self.brightness_delta))
        return img

    def contrast(self, img: np.ndarray) -> np.ndarray:
        """Contrast distortion.

        Args:
            img (np.ndarray): The input image.
        Returns:
            np.ndarray: Image after contrast change.
        """

        if random.randint(2):
            return self.convert(
                img,
                alpha=random.uniform(self.contrast_lower, self.contrast_upper))
        return img

    def saturation(self, img: np.ndarray) -> np.ndarray:
        """Saturation distortion.

        Args:
            img (np.ndarray): The input image.
        Returns:
            np.ndarray: Image after saturation change.
        """

        if random.randint(2):
            img = mmcv.bgr2hsv(img)
            img[:, :, 1] = self.convert(
                img[:, :, 1],
                alpha=random.uniform(self.saturation_lower,
                                     self.saturation_upper))
            img = mmcv.hsv2bgr(img)
        return img

    def hue(self, img: np.ndarray) -> np.ndarray:
        """Hue distortion.

        Args:
            img (np.ndarray): The input image.
        Returns:
            np.ndarray: Image after hue change.
        """

        if random.randint(2):
            img = mmcv.bgr2hsv(img)
            img[:, :,
                0] = (img[:, :, 0].astype(int) +
                      random.randint(-self.hue_delta, self.hue_delta)) % 180
            img = mmcv.hsv2bgr(img)
        return img

    def transform(self, results: dict) -> dict:
        """Transform function to perform photometric distortion on images.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            dict: Result dict with images distorted.
        """

        def _photo_metric_distortion(img, contrast_mode=None):
            # random brightness
            img = self.brightness(img)

            # mode == 0 --> do random contrast first
            # mode == 1 --> do random contrast last
            mode = contrast_mode or random.randint(2)
            if mode == 1:
                img = self.contrast(img)

            # random saturation
            img = self.saturation(img)

            # random hue
            img = self.hue(img)

            # random contrast
            if mode == 0:
                img = self.contrast(img)
            return img


        contrast_mode = random.randint(2) \
            if self.consistent_contrast_mode else None
        results['img'] = [_photo_metric_distortion(img, contrast_mode) \
                          for img in results['img']]

        return results

    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += (f'(brightness_delta={self.brightness_delta}, '
                     f'contrast_range=({self.contrast_lower}, '
                     f'{self.contrast_upper}), '
                     f'saturation_range=({self.saturation_lower}, '
                     f'{self.saturation_upper}), '
                     f'hue_delta={self.hue_delta}), '
                     f'consistent_contrast_mode={self.consistent_contrast_mode}')
        return repr_str


@TRANSFORMS.register_module()
class MultiImgRandomCutOut(BaseTransform):
    """CutOut operation.

    Randomly drop some regions of image used in
    `Cutout <https://arxiv.org/abs/1708.04552>`_.

    Required Keys:

    - img
    - gt_seg_map

    Modified Keys:

    - img
    - gt_seg_map

    Args:
        prob (float): cutout probability.
        n_holes (int | tuple[int, int]): Number of regions to be dropped.
            If it is given as a list, number of holes will be randomly
            selected from the closed interval [`n_holes[0]`, `n_holes[1]`].
        cutout_shape (tuple[int, int] | list[tuple[int, int]]): The candidate
            shape of dropped regions. It can be `tuple[int, int]` to use a
            fixed cutout shape, or `list[tuple[int, int]]` to randomly choose
            shape from the list.
        cutout_ratio (tuple[float, float] | list[tuple[float, float]]): The
            candidate ratio of dropped regions. It can be `tuple[float, float]`
            to use a fixed ratio or `list[tuple[float, float]]` to randomly
            choose ratio from the list. Please note that `cutout_shape`
            and `cutout_ratio` cannot be both given at the same time.
        fill_in (tuple[float, float, float] | tuple[int, int, int]): The value
            of pixel to fill in the dropped regions. Default: (0, 0, 0).
        seg_fill_in (int): The labels of pixel to fill in the dropped regions.
            If seg_fill_in is None, skip. Default: None.
    """

    def __init__(self,
                 prob,
                 n_holes,
                 cutout_shape=None,
                 cutout_ratio=None,
                 fill_in=(0, 0, 0),
                 seg_fill_in=None):

        assert 0 <= prob and prob <= 1
        assert (cutout_shape is None) ^ (cutout_ratio is None), \
            'Either cutout_shape or cutout_ratio should be specified.'
        assert (isinstance(cutout_shape, (list, tuple))
                or isinstance(cutout_ratio, (list, tuple)))
        if isinstance(n_holes, tuple):
            assert len(n_holes) == 2 and 0 <= n_holes[0] < n_holes[1]
        else:
            n_holes = (n_holes, n_holes)
        if seg_fill_in is not None:
            assert (isinstance(seg_fill_in, int) and 0 <= seg_fill_in
                    and seg_fill_in <= 255)
        self.prob = prob
        self.n_holes = n_holes
        self.fill_in = fill_in
        self.seg_fill_in = seg_fill_in
        self.with_ratio = cutout_ratio is not None
        self.candidates = cutout_ratio if self.with_ratio else cutout_shape
        if not isinstance(self.candidates, list):
            self.candidates = [self.candidates]

    @cache_randomness
    def do_cutout(self):
        return np.random.rand() < self.prob

    @cache_randomness
    def generate_patches(self, results):
        cutout = self.do_cutout()

        h, w, _ = results['img'][0].shape
        if cutout:
            n_holes = np.random.randint(self.n_holes[0], self.n_holes[1] + 1)
        else:
            n_holes = 0
        x1_lst = []
        y1_lst = []
        index_lst = []
        for _ in range(n_holes):
            x1_lst.append(np.random.randint(0, w))
            y1_lst.append(np.random.randint(0, h))
            index_lst.append(np.random.randint(0, len(self.candidates)))
        return cutout, n_holes, x1_lst, y1_lst, index_lst

    def transform(self, results: dict) -> dict:
        """Call function to drop some regions of image."""
        cutout, n_holes, x1_lst, y1_lst, index_lst = self.generate_patches(
            results)
        if cutout:
            h, w, c = results['img'][0].shape
            for i in range(n_holes):
                x1 = x1_lst[i]
                y1 = y1_lst[i]
                index = index_lst[i]
                if not self.with_ratio:
                    cutout_w, cutout_h = self.candidates[index]
                else:
                    cutout_w = int(self.candidates[index][0] * w)
                    cutout_h = int(self.candidates[index][1] * h)

                x2 = np.clip(x1 + cutout_w, 0, w)
                y2 = np.clip(y1 + cutout_h, 0, h)
                for idx in range(len(results['img'])):
                    results['img'][idx][y1:y2, x1:x2, :] = self.fill_in

                if self.seg_fill_in is not None:
                    for key in results.get('seg_fields', []):
                        results[key][y1:y2, x1:x2] = self.seg_fill_in

        return results

    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += f'(prob={self.prob}, '
        repr_str += f'n_holes={self.n_holes}, '
        repr_str += (f'cutout_ratio={self.candidates}, ' if self.with_ratio
                     else f'cutout_shape={self.candidates}, ')
        repr_str += f'fill_in={self.fill_in}, '
        repr_str += f'seg_fill_in={self.seg_fill_in})'
        return repr_str


@TRANSFORMS.register_module()
class MultiImgRandomRotFlip(BaseTransform):
    """Rotate and flip the image & seg or just rotate the image & seg.

    Required Keys:

    - img
    - gt_seg_map

    Modified Keys:

    - img
    - gt_seg_map

    Args:
        rotate_prob (float): The probability of rotate image.
        flip_prob (float): The probability of rotate&flip image.
        degree (float, tuple[float]): Range of degrees to select from. If
            degree is a number instead of tuple like (min, max),
            the range of degree will be (``-degree``, ``+degree``)
        pad_val (float, optional): Padding value of image. Default: 0.
        seg_pad_val (float, optional): Padding value of segmentation map.
            Default: 255.
    """

    def __init__(self,
                 rotate_prob=0.5,
                 flip_prob=0.5,
                 degree=(-20, 20),
                 pad_val=0,
                 seg_pad_val=255):
        self.rotate_prob = rotate_prob
        self.flip_prob = flip_prob
        self.pad_val = pad_val
        self.seg_pad_val = seg_pad_val
        assert 0 <= rotate_prob <= 1 and 0 <= flip_prob <= 1
        if isinstance(degree, (float, int)):
            assert degree > 0, f'degree {degree} should be positive'
            self.degree = (-degree, degree)
        else:
            self.degree = degree
        assert len(self.degree) == 2, f'degree {self.degree} should be a ' \
                                      f'tuple of (min, max)'

    def random_rot_flip(self, results: dict) -> dict:
        k = np.random.randint(0, 4)
        results['img'] = [np.rot90(img, k) for img in results['img']]
        for key in results.get('seg_fields', []):
            results[key] = np.rot90(results[key], k)
        axis = np.random.randint(0, 2)
        results['img'] = [
            np.flip(img, axis=axis).copy() for img in results['img']]
        for key in results.get('seg_fields', []):
            results[key] = np.flip(results[key], axis=axis).copy()
        return results

    def random_rotate(self, results: dict) -> dict:
        angle = np.random.uniform(min(*self.degree), max(*self.degree))
        results['img'] = [
            mmcv.imrotate(img, angle=angle,
                          border_value=self.pad_val) for img in results['img']]
        for key in results.get('seg_fields', []):
            results[key] = mmcv.imrotate(results[key],
                                         angle=angle,
                                         border_value=self.seg_pad_val,
                                         interpolation='nearest')
        return results

    def transform(self, results: dict) -> dict:
        """Call function to rotate or rotate & flip image, semantic
        segmentation maps.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            dict: Rotated or rotated & flipped results.
        """
        rotate_flag = 0
        if random.random() < self.rotate_prob:
            results = self.random_rotate(results)
            rotate_flag = 1
        if random.random() < self.flip_prob and rotate_flag == 0:
            results = self.random_rot_flip(results)
        return results

    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += f'(rotate_prob={self.rotate_prob}, ' \
                    f'flip_prob={self.flip_prob}, ' \
                    f'degree={self.degree})'
        return repr_str


@TRANSFORMS.register_module()
class MultiImgResizeShortestEdge(BaseTransform):
    """Resize the image and mask while keeping the aspect ratio unchanged.

    Modified from https://github.com/facebookresearch/detectron2/blob/main/detectron2/data/transforms/augmentation_impl.py#L130 # noqa:E501
    Copyright (c) Facebook, Inc. and its affiliates.
    Licensed under the Apache-2.0 License

    This transform attempts to scale the shorter edge to the given
    `scale`, as long as the longer edge does not exceed `max_size`.
    If `max_size` is reached, then downscale so that the longer
    edge does not exceed `max_size`.

    Required Keys:

    - img
    - gt_seg_map (optional)

    Modified Keys:

    - img
    - img_shape
    - gt_seg_map (optional)

    Added Keys:

    - scale
    - scale_factor
    - keep_ratio


    Args:
        scale (Union[int, Tuple[int, int]]): The target short edge length.
            If it's tuple, will select the min value as the short edge length.
        max_size (int): The maximum allowed longest edge length.
    """

    def __init__(self, scale: Union[int, Tuple[int, int]],
                 max_size: int) -> None:
        super().__init__()
        self.scale = scale
        self.max_size = max_size

        # Create a empty Resize object
        self.resize = TRANSFORMS.build({
            'type': 'MultiImgResize',
            'scale': 0,
            'keep_ratio': True
        })

    def _get_output_shape(self, img, short_edge_length) -> Tuple[int, int]:
        """Compute the target image shape with the given `short_edge_length`.

        Args:
            img (np.ndarray): The input image.
            short_edge_length (Union[int, Tuple[int, int]]): The target short
                edge length. If it's tuple, will select the min value as the
                short edge length.
        """
        h, w = img.shape[:2]
        if isinstance(short_edge_length, int):
            size = short_edge_length * 1.0
        elif isinstance(short_edge_length, tuple):
            size = min(short_edge_length) * 1.0
        scale = size / min(h, w)
        if h < w:
            new_h, new_w = size, scale * w
        else:
            new_h, new_w = scale * h, size

        if max(new_h, new_w) > self.max_size:
            scale = self.max_size * 1.0 / max(new_h, new_w)
            new_h *= scale
            new_w *= scale

        new_h = int(new_h + 0.5)
        new_w = int(new_w + 0.5)
        return (new_w, new_h)

    def transform(self, results: Dict) -> Dict:
        self.resize.scale = self._get_output_shape(results['img'], self.scale)
        return self.resize(results)


@TRANSFORMS.register_module()
class MultiImgExchangeTime(BaseTransform):
    """Exchange images of different times.
        Args:
            prob (float): probability of applying the transform. Default: 0.5.
    """
    def __init__(self,
                 prob: float = 0.5) -> None:

        assert 0 <= prob and prob <= 1
        self.prob = prob

    def transform(self, results: dict) -> dict:
        """Call function to exchange images ."""
        exchange = True if np.random.rand() < self.prob else False
        if exchange:
            results['img'].reverse()  # list.reverse()
            if 'gt_seg_map_from' in results['seg_fields'] and \
                'gt_seg_map_to' in results['seg_fields']:
                results['gt_seg_map_from'], results['gt_seg_map_to'] = \
                    results['gt_seg_map_to'], results['gt_seg_map_from']
        return results
        
    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += f'(prob={self.prob}, '
        return repr_str


@TRANSFORMS.register_module()
class MultiImgResize(BaseTransform):
    """Resize images & seg.
    This transform resizes the input image according to ``scale`` or
    ``scale_factor``. Bboxes, seg map and keypoints are then resized with the
    same scale factor.
    if ``scale`` and ``scale_factor`` are both set, it will use ``scale`` to
    resize.
    Required Keys:

    - img
    - gt_seg_map (optional)

    Modified Keys:

    - img
    - gt_seg_map
    - img_shape

    Added Keys:

    - scale
    - scale_factor
    - keep_ratio

    Args:
        scale (int or tuple): Images scales for resizing. Defaults to None
        scale_factor (float or tuple[float]): Scale factors for resizing.
            Defaults to None.
        keep_ratio (bool): Whether to keep the aspect ratio when resizing the
            image. Defaults to False.
        clip_object_border (bool): Whether to clip the objects
            outside the border of the image. In some dataset like MOT17, the gt
            bboxes are allowed to cross the border of images. Therefore, we
            don't need to clip the gt bboxes in these cases. Defaults to True.
        backend (str): Image resize backend, choices are 'cv2' and 'pillow'.
            These two backends generates slightly different results. Defaults
            to 'cv2'.
        interpolation (str): Interpolation method, accepted values are
            "nearest", "bilinear", "bicubic", "area", "lanczos" for 'cv2'
            backend, "nearest", "bilinear" for 'pillow' backend. Defaults
            to 'bilinear'.
    """

    def __init__(self,
                 scale: Optional[Union[int, Tuple[int, int]]] = None,
                 scale_factor: Optional[Union[float, Tuple[float,
                                                           float]]] = None,
                 keep_ratio: bool = False,
                 clip_object_border: bool = True,
                 backend: str = 'cv2',
                 interpolation='bilinear') -> None:
        assert scale is not None or scale_factor is not None, (
            '`scale` and'
            '`scale_factor` can not both be `None`')
        if scale is None:
            self.scale = None
        else:
            if isinstance(scale, int):
                self.scale = (scale, scale)
            else:
                self.scale = scale

        self.backend = backend
        self.interpolation = interpolation
        self.keep_ratio = keep_ratio
        self.clip_object_border = clip_object_border
        if scale_factor is None:
            self.scale_factor = None
        elif isinstance(scale_factor, float):
            self.scale_factor = (scale_factor, scale_factor)
        elif isinstance(scale_factor, tuple):
            assert (len(scale_factor)) == 2
            self.scale_factor = scale_factor
        else:
            raise TypeError(
                f'expect scale_factor is float or Tuple(float), but'
                f'get {type(scale_factor)}')

    def _resize_img(self, results: dict) -> None:
        """Resize images with ``results['scale']``."""

        if results.get('img', None) is not None:
            res_imgs = []
            for img in results['img']:
                if self.keep_ratio:
                    img, scale_factor = mmcv.imrescale(
                        img,
                        results['scale'],
                        interpolation=self.interpolation,
                        return_scale=True,
                        backend=self.backend)
                    # the w_scale and h_scale has minor difference
                    # a real fix should be done in the mmcv.imrescale in the future
                    new_h, new_w = img.shape[:2]
                    h, w = img.shape[:2]
                    w_scale = new_w / w
                    h_scale = new_h / h
                else:
                    img, w_scale, h_scale = mmcv.imresize(
                        img,
                        results['scale'],
                        interpolation=self.interpolation,
                        return_scale=True,
                        backend=self.backend)
                res_imgs.append(img)
            results['img'] = res_imgs
            results['img_shape'] = res_imgs[0].shape[:2]
            results['scale_factor'] = (w_scale, h_scale)
            results['keep_ratio'] = self.keep_ratio

    def _resize_seg(self, results: dict) -> None:
        """Resize semantic segmentation map with ``results['scale']``."""
        for key in results.get('seg_fields', []):
            if self.keep_ratio:
                gt_seg = mmcv.imrescale(
                    results[key], 
                    results['scale'], 
                    interpolation='nearest', 
                    backend=self.backend)
            else:
                gt_seg = mmcv.imresize(
                    results[key], 
                    results['scale'], 
                    interpolation='nearest',
                    backend=self.backend)
            results[key] = gt_seg

    def transform(self, results: dict) -> dict:
        """Transform function to resize images, semantic
        segmentation map.
        Args:
            results (dict): Result dict from loading pipeline.
        Returns:
            dict: Resized results, 'img', 'gt_seg_map',
            'scale', 'scale_factor', 'img_shape',
            and 'keep_ratio' keys are updated in result dict.
        """

        if self.scale:
            results['scale'] = self.scale
        else:
            img_shape = results['img'][0].shape[:2]
            results['scale'] = _scale_size(img_shape[::-1],
                                           self.scale_factor)  # type: ignore
        self._resize_img(results)
        self._resize_seg(results)
        return results

    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += f'(scale={self.scale}, '
        repr_str += f'scale_factor={self.scale_factor}, '
        repr_str += f'keep_ratio={self.keep_ratio}, '
        repr_str += f'clip_object_border={self.clip_object_border}), '
        repr_str += f'backend={self.backend}), '
        repr_str += f'interpolation={self.interpolation})'
        return repr_str


@TRANSFORMS.register_module()
class MultiImgRandomResize(BaseTransform):
    """Random resize images.
    How to choose the target scale to resize the image will follow the rules
    below:
    - if ``scale`` is a sequence of tuple
    .. math::
        target\\_scale[0] \\sim Uniform([scale[0][0], scale[1][0]])
    .. math::
        target\\_scale[1] \\sim Uniform([scale[0][1], scale[1][1]])
    Following the resize order of weight and height in cv2, ``scale[i][0]``
    is for width, and ``scale[i][1]`` is for height.
    - if ``scale`` is a tuple
    .. math::
        target\\_scale[0] \\sim Uniform([ratio\\_range[0], ratio\\_range[1]])
            * scale[0]
    .. math::
        target\\_scale[0] \\sim Uniform([ratio\\_range[0], ratio\\_range[1]])
            * scale[1]
    Following the resize order of weight and height in cv2, ``ratio_range[0]``
    is for width, and ``ratio_range[1]`` is for height.
    - if ``keep_ratio`` is True, the minimum value of ``target_scale`` will be
      used to set the shorter side and the maximum value will be used to
      set the longer side.
    - if ``keep_ratio`` is False, the value of ``target_scale`` will be used to
      reisze the width and height accordingly.
    Required Keys:

    - img
    - gt_seg_map

    Modified Keys:

    - img
    - gt_seg_map
    - img_shape
    
    Added Keys:

    - scale
    - scale_factor
    - keep_ratio

    Args:
        scale (tuple or Sequence[tuple]): Images scales for resizing.
            Defaults to None.
        ratio_range (tuple[float], optional): (min_ratio, max_ratio).
            Defaults to None.
        resize_type (str): The type of resize class to use. Defaults to
            "Resize".
        **resize_kwargs: Other keyword arguments for the ``resize_type``.
    Note:
        By defaults, the ``resize_type`` is "Resize", if it's not overwritten
        by your registry, it indicates the :class:`mmcv.Resize`. And therefore,
        ``resize_kwargs`` accepts any keyword arguments of it, like
        ``keep_ratio``, ``interpolation`` and so on.
        If you want to use your custom resize class, the class should accept
        ``scale`` argument and have ``scale`` attribution which determines the
        resize shape.
    """

    def __init__(
        self,
        scale: Union[Tuple[int, int], Sequence[Tuple[int, int]]],
        ratio_range: Tuple[float, float] = None,
        resize_type: str = 'MultiImgResize',
        **resize_kwargs,
    ) -> None:

        self.scale = scale
        self.ratio_range = ratio_range

        self.resize_cfg = dict(type=resize_type, **resize_kwargs)
        # create a empty Reisize object
        self.resize = TRANSFORMS.build({'scale': 0, **self.resize_cfg})

    @staticmethod
    def _random_sample(scales: Sequence[Tuple[int, int]]) -> tuple:
        """Private function to randomly sample a scale from a list of tuples.
        Args:
            scales (list[tuple]): Images scale range for sampling.
                There must be two tuples in scales, which specify the lower
                and upper bound of image scales.
        Returns:
            tuple: The targeted scale of the image to be resized.
        """

        assert is_list_of(scales, tuple) and len(scales) == 2
        scale_0 = [scales[0][0], scales[1][0]]
        scale_1 = [scales[0][1], scales[1][1]]
        edge_0 = np.random.randint(min(scale_0), max(scale_0) + 1)
        edge_1 = np.random.randint(min(scale_1), max(scale_1) + 1)
        scale = (edge_0, edge_1)
        return scale

    @staticmethod
    def _random_sample_ratio(scale: tuple, ratio_range: Tuple[float,
                                                              float]) -> tuple:
        """Private function to randomly sample a scale from a tuple.
        A ratio will be randomly sampled from the range specified by
        ``ratio_range``. Then it would be multiplied with ``scale`` to
        generate sampled scale.
        Args:
            scale (tuple): Images scale base to multiply with ratio.
            ratio_range (tuple[float]): The minimum and maximum ratio to scale
                the ``scale``.
        Returns:
            tuple: The targeted scale of the image to be resized.
        """

        assert isinstance(scale, tuple) and len(scale) == 2
        min_ratio, max_ratio = ratio_range
        assert min_ratio <= max_ratio
        ratio = np.random.random_sample() * (max_ratio - min_ratio) + min_ratio
        scale = int(scale[0] * ratio), int(scale[1] * ratio)
        return scale

    @cache_randomness
    def _random_scale(self) -> tuple:
        """Private function to randomly sample an scale according to the type
        of ``scale``.
        Returns:
            tuple: The targeted scale of the image to be resized.
        """

        if is_tuple_of(self.scale, int):
            assert self.ratio_range is not None and len(self.ratio_range) == 2
            scale = self._random_sample_ratio(
                self.scale,  # type: ignore
                self.ratio_range)
        elif is_seq_of(self.scale, tuple):
            scale = self._random_sample(self.scale)  # type: ignore
        else:
            raise NotImplementedError('Do not support sampling function '
                                      f'for "{self.scale}"')

        return scale

    def transform(self, results: dict) -> dict:
        """Transform function to resize images, bounding boxes, semantic
        segmentation map.
        Args:
            results (dict): Result dict from loading pipeline.
        Returns:
            dict: Resized results, ``img``, ``gt_semantic_seg``,
            ``scale``, ``scale_factor``, ``img_shape``, and
            ``keep_ratio`` keys are updated in result dict.
        """
        results['scale'] = self._random_scale()
        self.resize.scale = results['scale']
        results = self.resize(results)
        return results

    def __repr__(self) -> str:
        repr_str = self.__class__.__name__
        repr_str += f'(scale={self.scale}, '
        repr_str += f'ratio_range={self.ratio_range}, '
        repr_str += f'resize_cfg={self.resize_cfg})'
        return repr_str
    

@TRANSFORMS.register_module()
class MultiImgNormalize(BaseTransform):
    """Normalize the images.
    Required Keys:

    - img

    Modified Keys:

    - img

    Added Keys:

    - img_norm_cfg
      - mean
      - std
      - to_rgb
      
    Args:
        mean (sequence): Mean values of 3 channels.
        std (sequence): Std values of 3 channels.
        to_rgb (bool): Whether to convert the image from BGR to RGB before
            normlizing the image. If ``to_rgb=True``, the order of mean and std
            should be RGB. If ``to_rgb=False``, the order of mean and std
            should be the same order of the image. Defaults to True.
    """

    def __init__(self,
                 mean: Sequence[Union[int, float]],
                 std: Sequence[Union[int, float]],
                 to_rgb: bool = True) -> None:
        self.mean = np.array(mean, dtype=np.float32)
        self.std = np.array(std, dtype=np.float32)
        self.to_rgb = to_rgb

    def transform(self, results: dict) -> dict:
        """Function to normalize images.
        Args:
            results (dict): Result dict from loading pipeline.
        Returns:
            dict: Normalized results, key 'img_norm_cfg' key is added in to
            result dict.
        """

        results['img'] = [
            mmcv.imnormalize(img, self.mean, self.std, self.to_rgb)
            for img in results['img']]
        results['img_norm_cfg'] = dict(
            mean=self.mean, std=self.std, to_rgb=self.to_rgb)
        return results

    def __repr__(self) -> str:
        repr_str = self.__class__.__name__
        repr_str += f'(mean={self.mean}, std={self.std}, to_rgb={self.to_rgb})'
        return repr_str


@TRANSFORMS.register_module()
class MultiImgRandomFlip(BaseTransform):
    """Flip the image & segmentation map. Added or Updated
    keys: flip, flip_direction, img, gt_bboxes, gt_seg_map, and
    gt_keypoints. There are 3 flip modes:

    - ``prob`` is float, ``direction`` is string: the image will be
      ``direction``ly flipped with probability of ``prob`` .
      E.g., ``prob=0.5``, ``direction='horizontal'``,
      then image will be horizontally flipped with probability of 0.5.

    - ``prob`` is float, ``direction`` is list of string: the image will
      be ``direction[i]``ly flipped with probability of
      ``prob/len(direction)``.
      E.g., ``prob=0.5``, ``direction=['horizontal', 'vertical']``,
      then image will be horizontally flipped with probability of 0.25,
      vertically with probability of 0.25.

    - ``prob`` is list of float, ``direction`` is list of string:
      given ``len(prob) == len(direction)``, the image will
      be ``direction[i]``ly flipped with probability of ``prob[i]``.
      E.g., ``prob=[0.3, 0.5]``, ``direction=['horizontal',
      'vertical']``, then image will be horizontally flipped with
      probability of 0.3, vertically with probability of 0.5.

    Required Keys:

    - img
    - gt_seg_map

    Modified Keys:

    - img
    - gt_seg_map

    Added Keys:

    - flip
    - flip_direction

    Args:
        prob (float | list[float], optional): The flipping probability.
            Defaults to None.
        direction(str | list[str]): The flipping direction. Options
            If input is a list, the length must equal ``prob``. Each
            element in ``prob`` indicates the flip probability of
            corresponding direction. Defaults to 'horizontal'.
    """

    def __init__(self,
                 prob: Optional[Union[float, Iterable[float]]] = None,
                 direction: Union[str, Sequence[Optional[str]]] = 'horizontal') -> None:
        
        if isinstance(prob, list):
            assert is_list_of(prob, float)
            assert 0 <= sum(prob) <= 1
        elif isinstance(prob, float):
            assert 0 <= prob <= 1
        else:
            raise ValueError(f'probs must be float or list of float, but \
                              got `{type(prob)}`.')
        self.prob = prob

        valid_directions = ['horizontal', 'vertical', 'diagonal']
        if isinstance(direction, str):
            assert direction in valid_directions
        elif isinstance(direction, list):
            assert is_list_of(direction, str)
            assert set(direction).issubset(set(valid_directions))
        else:
            raise ValueError(f'direction must be either str or list of str, \
                               but got `{type(direction)}`.')
        self.direction = direction

        if isinstance(prob, list):
            assert len(prob) == len(self.direction)

    @cache_randomness
    def _choose_direction(self) -> str:
        """Choose the flip direction according to `prob` and `direction`"""
        if isinstance(self.direction,
                      Sequence) and not isinstance(self.direction, str):
            # None means non-flip
            direction_list: list = list(self.direction) + [None]
        elif isinstance(self.direction, str):
            # None means non-flip
            direction_list = [self.direction, None]

        if isinstance(self.prob, list):
            non_prob: float = 1 - sum(self.prob)
            prob_list = self.prob + [non_prob]
        elif isinstance(self.prob, float):
            non_prob = 1. - self.prob
            # exclude non-flip
            single_ratio = self.prob / (len(direction_list) - 1)
            prob_list = [single_ratio] * (len(direction_list) - 1) + [non_prob]

        cur_dir = np.random.choice(direction_list, p=prob_list)

        return cur_dir

    def transform(self, results: dict) -> dict:
        """Transform function to flip images, semantic
        segmentation map.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            dict: Flipped results, 'img', 'gt_seg_map',
            'flip', and 'flip_direction' keys are
            updated in result dict.
        """

        cur_dir = self._choose_direction()
        if cur_dir is None:
            results['flip'] = False
            results['flip_direction'] = None
        else:
            results['flip'] = True
            results['flip_direction'] = cur_dir

            # flip image
            results['img'] = [
                mmcv.imflip(img, direction=results['flip_direction'])
                for img in results['img']
            ]

            # flip segs
            for key in results.get('seg_fields', []):
                # use copy() to make numpy stride positive
                results[key] = mmcv.imflip(
                    results[key], direction=results['flip_direction']).copy()
        return results


    def __repr__(self) -> str:
        repr_str = self.__class__.__name__
        repr_str += f'(prob={self.prob}, '
        repr_str += f'direction={self.direction})'

        return repr_str


@TRANSFORMS.register_module()
class MultiImgPad(BaseTransform):
    """Pad the image & segmentation map.

    There are three padding modes: (1) pad to a fixed size and (2) pad to the
    minimum size that is divisible by some number. and (3)pad to square. Also,
    pad to square and pad to the minimum size can be used as the same time.

    Required Keys:

    - img
    - gt_seg_map

    Modified Keys:

    - img
    - gt_seg_map
    - img_shape

    Added Keys:

    - pad_shape
    - pad_fixed_size
    - pad_size_divisor

    Args:
        size (tuple, optional): Fixed padding size.
            Expected padding shape (w, h). Defaults to None.
        size_divisor (int, optional): The divisor of padded size. Defaults to
            None.
        pad_to_square (bool): Whether to pad the image into a square.
            Currently only used for YOLOX. Defaults to False.
        pad_val (Number | dict[str, Number], optional): Padding value for if
            the pad_mode is "constant". If it is a single number, the value
            to pad the image is the number and to pad the semantic
            segmentation map is 255. If it is a dict, it should have the
            following keys:

            - img: The value to pad the image.
            - seg: The value to pad the semantic segmentation map.

            Defaults to dict(img=0, seg=255).
        padding_mode (str): Type of padding. Should be: constant, edge,
            reflect or symmetric. Defaults to 'constant'.

            - constant: pads with a constant value, this value is specified
              with pad_val.
            - edge: pads with the last value at the edge of the image.
            - reflect: pads with reflection of image without repeating the last
              value on the edge. For example, padding [1, 2, 3, 4] with 2
              elements on both sides in reflect mode will result in
              [3, 2, 1, 2, 3, 4, 3, 2].
            - symmetric: pads with reflection of image repeating the last value
              on the edge. For example, padding [1, 2, 3, 4] with 2 elements on
              both sides in symmetric mode will result in
              [2, 1, 1, 2, 3, 4, 4, 3]
    """

    def __init__(self,
                 size: Optional[Tuple[int, int]] = None,
                 size_divisor: Optional[int] = None,
                 pad_to_square: bool = False,
                 pad_val: Union[int, float, dict] = dict(img=0, seg=255),
                 padding_mode: str = 'constant') -> None:
        self.size = size
        self.size_divisor = size_divisor
        if isinstance(pad_val, int):
            pad_val = dict(img=pad_val, seg=255)
        assert isinstance(pad_val, dict), 'pad_val '
        self.pad_val = pad_val
        self.pad_to_square = pad_to_square

        if pad_to_square:
            assert size is None, \
                'The size and size_divisor must be None ' \
                'when pad2square is True'
        else:
            assert size is not None or size_divisor is not None, \
                'only one of size and size_divisor should be valid'
            assert size is None or size_divisor is None
        assert padding_mode in ['constant', 'edge', 'reflect', 'symmetric']
        self.padding_mode = padding_mode

    def _pad_img(self, results: dict) -> None:
        """Pad images according to ``self.size``."""
        pad_val = self.pad_val.get('img', 0)

        size = None
        if self.pad_to_square:
            max_size = max(results['img'][0].shape[:2])
            size = (max_size, max_size)
        if self.size_divisor is not None:
            if size is None:
                size = (results['img'][0].shape[0], results['img'].shape[1])
            pad_h = int(np.ceil(
                size[0] / self.size_divisor)) * self.size_divisor
            pad_w = int(np.ceil(
                size[1] / self.size_divisor)) * self.size_divisor
            size = (pad_h, pad_w)
        elif self.size is not None:
            size = self.size[::-1]
        if isinstance(pad_val, int) and results['img'][0].ndim == 3:
            pad_val = tuple(pad_val for _ in range(results['img'][0].shape[2]))
        
        padded_imgs = [
            mmcv.impad(
                img,
                shape=size,
                pad_val=pad_val,
                padding_mode=self.padding_mode) for img in results['img']]

        results['img'] = padded_imgs
        results['pad_shape'] = padded_imgs[0].shape
        results['pad_fixed_size'] = self.size
        results['pad_size_divisor'] = self.size_divisor
        results['img_shape'] = padded_imgs[0].shape[:2]

    def _pad_seg(self, results: dict) -> None:
        """Pad semantic segmentation map according to
        ``results['pad_shape']``."""
        pad_val = self.pad_val.get('seg', 255)
        for key in results.get('seg_fields', []):
            results[key] = mmcv.impad(
                results[key],
                shape=results['pad_shape'][:2],
                pad_val=pad_val,
                padding_mode=self.padding_mode)

    def transform(self, results: dict) -> dict:
        """Call function to pad images, masks, semantic segmentation maps.

        Args:
            results (dict): Result dict from loading pipeline.

        Returns:
            dict: Updated result dict.
        """
        self._pad_img(results)
        self._pad_seg(results)
        return results

    def __repr__(self):
        repr_str = self.__class__.__name__
        repr_str += f'(size={self.size}, '
        repr_str += f'size_divisor={self.size_divisor}, '
        repr_str += f'pad_to_square={self.pad_to_square}, '
        repr_str += f'pad_val={self.pad_val}), '
        repr_str += f'padding_mode={self.padding_mode})'
        return repr_str


@TRANSFORMS.register_module()
class MultiImgAlbu(BaseTransform):
    """Albumentation augmentation. Adds custom transformations from
    Albumentations library. Please, visit
    `https://albumentations.readthedocs.io` to get more information. An example
    of ``transforms`` is as followed:
    .. code-block::
        [
            dict(
                type='ShiftScaleRotate',
                shift_limit=0.0625,
                scale_limit=0.0,
                rotate_limit=0,
                interpolation=1,
                p=0.5),
            dict(
                type='RandomBrightnessContrast',
                brightness_limit=[0.1, 0.3],
                contrast_limit=[0.1, 0.3],
                p=0.2),
            dict(type='ChannelShuffle', p=0.1),
            dict(
                type='OneOf',
                transforms=[
                    dict(type='Blur', blur_limit=3, p=1.0),
                    dict(type='MedianBlur', blur_limit=3, p=1.0)
                ],
                p=0.1),
        ]
    Args:
        transforms (list[dict]): A list of albu transformations
        keymap (dict): Contains {'input key':'albumentation-style key'}
        update_pad_shape (bool): Whether update final shape.
        additional_targets (dict): Dict with keys - new target name, 
        values - old target name. ex: {'image2': 'image'}.
    """
    def __init__(self, 
                 transforms: List[dict], 
                 keymap: dict = None, 
                 update_pad_shape: bool = False,
                 additional_targets: dict = None) -> None:
        # Args will be modified later, copying it will be safer
        transforms = copy.deepcopy(transforms)
        if keymap is not None:
            keymap = copy.deepcopy(keymap)
        self.transforms = transforms
        self.filter_lost_elements = False
        self.update_pad_shape = update_pad_shape
        self.additional_targets = additional_targets
        
        self.aug = Compose([self.albu_builder(t) for t in self.transforms], \
                           additional_targets=self.additional_targets)

        if not keymap:
            self.keymap_to_albu = {'img': 'image', 'gt_semantic_seg': 'mask'}
        else:
            self.keymap_to_albu = keymap
        self.keymap_back = {v: k for k, v in self.keymap_to_albu.items()}

    def albu_builder(self, cfg):
        """Import a module from albumentations.

        It inherits some of :func:`build_from_cfg` logic.
        Args:
            cfg (dict): Config dict. It should at least contain the key "type".
        Returns:
            obj: The constructed object.
        """

        assert isinstance(cfg, dict) and 'type' in cfg
        args = cfg.copy()

        obj_type = args.pop('type')
        if is_str(obj_type):
            obj_cls = getattr(albumentations, obj_type)
        else:
            raise TypeError(f'type must be str, but got {type(obj_type)}')

        if 'transforms' in args:
            args['transforms'] = [	
                self.albu_builder(transform)
                for transform in args['transforms']
            ]

        return obj_cls(**args)

    @staticmethod
    def mapper(d: dict, keymap: dict) -> dict:
        """Dictionary mapper.

        Renames keys according to keymap provided.
        Args:
            d (dict): old dict
            keymap (dict): {'old_key':'new_key'}
        Returns:
            dict: new dict.
        """

        updated_dict = {}
        for k, v in zip(d.keys(), d.values()):
            new_k = keymap.get(k, k)
            updated_dict[new_k] = d[k]

        if updated_dict.get('image', None) is not None:
            updated_dict['image'] = np.concatenate(updated_dict['image'], axis=-1)
        if updated_dict.get('img', None) is not None:
            updated_dict['img'] = np.split(updated_dict['img'], indices_or_sections=2, axis=-1)
        return updated_dict

    def transform(self, results: dict) -> dict:
        # dict to albumentations format
        results = self.mapper(results, self.keymap_to_albu)

        results = self.aug(**results)
        # back to the original format
        results = self.mapper(results, self.keymap_back)

        # update final shape
        if self.update_pad_shape:
            results['pad_shape'] = results['img'][0].shape

        return results

    def __repr__(self) -> str:
        repr_str = self.__class__.__name__ 
        repr_str += f'(transforms={self.transforms}, '
        repr_str += f'(update_pad_shape={self.update_pad_shape}, '
        repr_str += f'(additional_targets={self.additional_targets})'
        return repr_str