Table of Contents
Shortcuts

# Source code for mmseg.datasets.pipelines.transforms

    import mmcv
    import numpy as np
    from mmcv.utils import deprecated_api_warning, is_tuple_of
    from numpy import random

    from ..builder import PIPELINES

    @PIPELINES.register_module()
    class Resize(object):
        """Resize images & seg.

        This transform resizes the input image to some scale. If the input dict
        contains the key "scale", then the scale in the input dict is used,
        otherwise the specified scale in the init method is used.

        ``img_scale`` can be Nong, a tuple (single-scale) or a list of tuple
        (multi-scale). There are 4 multiscale modes:

        - ``ratio_range is not None``:
        1. When img_scale is None, img_scale is the shape of image in results
            (img_scale = results['img'].shape[:2]) and the image is resized based
            on the original size. (mode 1)
        2. When img_scale is a tuple (single-scale), randomly sample a ratio from
            the ratio range and multiply it with the image scale. (mode 2)

        - ``ratio_range is None and multiscale_mode == "range"``: randomly sample a
        scale from the a range. (mode 3)

        - ``ratio_range is None and multiscale_mode == "value"``: randomly sample a
        scale from multiple scales. (mode 4)

        Args:
            img_scale (tuple or list[tuple]): Images scales for resizing.
            multiscale_mode (str): Either "range" or "value".
            ratio_range (tuple[float]): (min_ratio, max_ratio)
            keep_ratio (bool): Whether to keep the aspect ratio when resizing the
                image.
        """

        def __init__(self,
                     img_scale=None,
                     multiscale_mode='range',
                     ratio_range=None,
                     keep_ratio=True):
            if img_scale is None:
                self.img_scale = None
            else:
                if isinstance(img_scale, list):
                    self.img_scale = img_scale
                else:
                    self.img_scale = [img_scale]
                assert mmcv.is_list_of(self.img_scale, tuple)

            if ratio_range is not None:
                # mode 1: given img_scale=None and a range of image ratio
                # mode 2: given a scale and a range of image ratio
                assert self.img_scale is None or len(self.img_scale) == 1
            else:
                # mode 3 and 4: given multiple scales or a range of scales
                assert multiscale_mode in ['value', 'range']

            self.multiscale_mode = multiscale_mode
            self.ratio_range = ratio_range
            self.keep_ratio = keep_ratio

        @staticmethod
        def random_select(img_scales):
            """Randomly select an img_scale from given candidates.

            Args:
                img_scales (list[tuple]): Images scales for selection.

            Returns:
                (tuple, int): Returns a tuple ``(img_scale, scale_dix)``,
                    where ``img_scale`` is the selected image scale and
                    ``scale_idx`` is the selected index in the given candidates.
            """

            assert mmcv.is_list_of(img_scales, tuple)
            scale_idx = np.random.randint(len(img_scales))
            img_scale = img_scales[scale_idx]
            return img_scale, scale_idx

        @staticmethod
        def random_sample(img_scales):
            """Randomly sample an img_scale when ``multiscale_mode=='range'``.

            Args:
                img_scales (list[tuple]): Images scale range for sampling.
                    There must be two tuples in img_scales, which specify the lower
                    and uper bound of image scales.

            Returns:
                (tuple, None): Returns a tuple ``(img_scale, None)``, where
                    ``img_scale`` is sampled scale and None is just a placeholder
                    to be consistent with :func:`random_select`.
            """

            assert mmcv.is_list_of(img_scales, tuple) and len(img_scales) == 2
            img_scale_long = [max(s) for s in img_scales]
            img_scale_short = [min(s) for s in img_scales]
            long_edge = np.random.randint(
                min(img_scale_long),
                max(img_scale_long) + 1)
            short_edge = np.random.randint(
                min(img_scale_short),
                max(img_scale_short) + 1)
            img_scale = (long_edge, short_edge)
            return img_scale, None

        @staticmethod
        def random_sample_ratio(img_scale, ratio_range):
            """Randomly sample an img_scale when ``ratio_range`` is specified.

            A ratio will be randomly sampled from the range specified by
            ``ratio_range``. Then it would be multiplied with ``img_scale`` to
            generate sampled scale.

            Args:
                img_scale (tuple): Images scale base to multiply with ratio.
                ratio_range (tuple[float]): The minimum and maximum ratio to scale
                    the ``img_scale``.

            Returns:
                (tuple, None): Returns a tuple ``(scale, None)``, where
                    ``scale`` is sampled ratio multiplied with ``img_scale`` and
                    None is just a placeholder to be consistent with
                    :func:`random_select`.
            """

            assert isinstance(img_scale, tuple) and len(img_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(img_scale[0] * ratio), int(img_scale[1] * ratio)
            return scale, None

        def _random_scale(self, results):
            """Randomly sample an img_scale according to ``ratio_range`` and
            ``multiscale_mode``.

            If ``ratio_range`` is specified, a ratio will be sampled and be
            multiplied with ``img_scale``.
            If multiple scales are specified by ``img_scale``, a scale will be
            sampled according to ``multiscale_mode``.
            Otherwise, single scale will be used.

            Args:
                results (dict): Result dict from :obj:`dataset`.

            Returns:
                dict: Two new keys 'scale` and 'scale_idx` are added into
                    ``results``, which would be used by subsequent pipelines.
            """

            if self.ratio_range is not None:
                if self.img_scale is None:
                    h, w = results['img'].shape[:2]
                    scale, scale_idx = self.random_sample_ratio((w, h),
                                                                self.ratio_range)
                else:
                    scale, scale_idx = self.random_sample_ratio(
                        self.img_scale[0], self.ratio_range)
            elif len(self.img_scale) == 1:
                scale, scale_idx = self.img_scale[0], 0
            elif self.multiscale_mode == 'range':
                scale, scale_idx = self.random_sample(self.img_scale)
            elif self.multiscale_mode == 'value':
                scale, scale_idx = self.random_select(self.img_scale)
            else:
                raise NotImplementedError

            results['scale'] = scale
            results['scale_idx'] = scale_idx

        def _resize_img(self, results):
            """Resize images with ``results['scale']``."""
            if self.keep_ratio:
                img, scale_factor = mmcv.imrescale(
                    results['img'], results['scale'], return_scale=True)
                # 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 = results['img'].shape[:2]
                w_scale = new_w / w
                h_scale = new_h / h
            else:
                img, w_scale, h_scale = mmcv.imresize(
                    results['img'], results['scale'], return_scale=True)
            scale_factor = np.array([w_scale, h_scale, w_scale, h_scale],
                                    dtype=np.float32)
            results['img'] = img
            results['img_shape'] = img.shape
            results['pad_shape'] = img.shape  # in case that there is no padding
            results['scale_factor'] = scale_factor
            results['keep_ratio'] = self.keep_ratio

        def _resize_seg(self, results):
            """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')
                else:
                    gt_seg = mmcv.imresize(
                        results[key], results['scale'], interpolation='nearest')
                results[key] = gt_seg

        def __call__(self, results):
            """Call function to resize images, bounding boxes, masks, semantic
            segmentation map.

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

            Returns:
                dict: Resized results, 'img_shape', 'pad_shape', 'scale_factor',
                    'keep_ratio' keys are added into result dict.
            """

            if 'scale' not in results:
                self._random_scale(results)
            self._resize_img(results)
            self._resize_seg(results)
            return results

        def __repr__(self):
            repr_str = self.__class__.__name__
            repr_str += (f'(img_scale={self.img_scale}, '
                         f'multiscale_mode={self.multiscale_mode}, '
                         f'ratio_range={self.ratio_range}, '
                         f'keep_ratio={self.keep_ratio})')
            return repr_str

    @PIPELINES.register_module()
    class RandomFlip(object):
        """Flip the image & seg.

        If the input dict contains the key "flip", then the flag will be used,
        otherwise it will be randomly decided by a ratio specified in the init
        method.

        Args:
            prob (float, optional): The flipping probability. Default: None.
            direction(str, optional): The flipping direction. Options are
                'horizontal' and 'vertical'. Default: 'horizontal'.
        """

        @deprecated_api_warning({'flip_ratio': 'prob'}, cls_name='RandomFlip')
        def __init__(self, prob=None, direction='horizontal'):
            self.prob = prob
            self.direction = direction
            if prob is not None:
                assert prob >= 0 and prob <= 1
            assert direction in ['horizontal', 'vertical']

        def __call__(self, results):
            """Call function to flip bounding boxes, masks, semantic segmentation
            maps.

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

            Returns:
                dict: Flipped results, 'flip', 'flip_direction' keys are added into
                    result dict.
            """

            if 'flip' not in results:
                flip = True if np.random.rand() < self.prob else False
                results['flip'] = flip
            if 'flip_direction' not in results:
                results['flip_direction'] = self.direction
            if results['flip']:
                # flip image
                results['img'] = mmcv.imflip(
                    results['img'], direction=results['flip_direction'])

                # 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):
            return self.__class__.__name__ + f'(prob={self.prob})'

    @PIPELINES.register_module()
    class Pad(object):
        """Pad the image & mask.

        There are two padding modes: (1) pad to a fixed size and (2) pad to the
        minimum size that is divisible by some number.
        Added keys are "pad_shape", "pad_fixed_size", "pad_size_divisor",

        Args:
            size (tuple, optional): Fixed padding size.
            size_divisor (int, optional): The divisor of padded size.
            pad_val (float, optional): Padding value. Default: 0.
            seg_pad_val (float, optional): Padding value of segmentation map.
                Default: 255.
        """

        def __init__(self,
                     size=None,
                     size_divisor=None,
                     pad_val=0,
                     seg_pad_val=255):
            self.size = size
            self.size_divisor = size_divisor
            self.pad_val = pad_val
            self.seg_pad_val = seg_pad_val
            # only one of size and size_divisor should be valid
            assert size is not None or size_divisor is not None
            assert size is None or size_divisor is None

        def _pad_img(self, results):
            """Pad images according to ``self.size``."""
            if self.size is not None:
                padded_img = mmcv.impad(
                    results['img'], shape=self.size, pad_val=self.pad_val)
            elif self.size_divisor is not None:
                padded_img = mmcv.impad_to_multiple(
                    results['img'], self.size_divisor, pad_val=self.pad_val)
            results['img'] = padded_img
            results['pad_shape'] = padded_img.shape
            results['pad_fixed_size'] = self.size
            results['pad_size_divisor'] = self.size_divisor

        def _pad_seg(self, results):
            """Pad masks according to ``results['pad_shape']``."""
            for key in results.get('seg_fields', []):
                results[key] = mmcv.impad(
                    results[key],
                    shape=results['pad_shape'][:2],
                    pad_val=self.seg_pad_val)

        def __call__(self, results):
            """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}, size_divisor={self.size_divisor}, ' \
                        f'pad_val={self.pad_val})'
            return repr_str

    @PIPELINES.register_module()
    class Normalize(object):
        """Normalize the image.

        Added key is "img_norm_cfg".

        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,
                default is true.
        """

        def __init__(self, mean, std, to_rgb=True):
            self.mean = np.array(mean, dtype=np.float32)
            self.std = np.array(std, dtype=np.float32)
            self.to_rgb = to_rgb

        def __call__(self, results):
            """Call function to normalize images.

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

            Returns:
                dict: Normalized results, 'img_norm_cfg' key is added into
                    result dict.
            """

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

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

    @PIPELINES.register_module()
    class Rerange(object):
        """Rerange the image pixel value.

        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 __call__(self, results):
            """Call function to rerange images.

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

            img = results['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
            results['img'] = 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

    @PIPELINES.register_module()
    class CLAHE(object):
        """Use CLAHE method to process the image.

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

        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 __call__(self, results):
            """Call function to Use CLAHE method process images.

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

            Returns:
                dict: Processed results.
            """

            for i in range(results['img'].shape[2]):
                results['img'][:, :, i] = mmcv.clahe(
                    np.array(results['img'][:, :, i], dtype=np.uint8),
                    self.clip_limit, self.tile_grid_size)

            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

    @PIPELINES.register_module()
    class RandomCrop(object):
        """Random crop the image & seg.

        Args:
            crop_size (tuple): Expected size after cropping, (h, w).
            cat_max_ratio (float): The maximum ratio that single category could
                occupy.
        """

        def __init__(self, crop_size, cat_max_ratio=1., ignore_index=255):
            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

        def get_crop_bbox(self, img):
            """Randomly get a crop bounding box."""
            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

        def crop(self, img, crop_bbox):
            """Crop from ``img``"""
            crop_y1, crop_y2, crop_x1, crop_x2 = crop_bbox
            img = img[crop_y1:crop_y2, crop_x1:crop_x2, ...]
            return img

        def __call__(self, results):
            """Call 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.
            """

            img = results['img']
            crop_bbox = self.get_crop_bbox(img)
            if self.cat_max_ratio < 1.:
                # Repeat 10 times
                for _ in range(10):
                    seg_temp = self.crop(results['gt_semantic_seg'], 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 = self.get_crop_bbox(img)

            # crop the image
            img = self.crop(img, crop_bbox)
            img_shape = img.shape
            results['img'] = img
            results['img_shape'] = img_shape

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

            return results

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

    @PIPELINES.register_module()
    class RandomRotate(object):
        """Rotate the image & seg.

        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

        def __call__(self, results):
            """Call function to rotate image, semantic segmentation maps.

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

            Returns:
                dict: Rotated results.
            """

            rotate = True if np.random.rand() < self.prob else False
            degree = np.random.uniform(min(*self.degree), max(*self.degree))
            if rotate:
                # rotate image
                results['img'] = mmcv.imrotate(
                    results['img'],
                    angle=degree,
                    border_value=self.pal_val,
                    center=self.center,
                    auto_bound=self.auto_bound)

                # 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

    @PIPELINES.register_module()
    class RGB2Gray(object):
        """Convert RGB image to grayscale image.

        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 __call__(self, results):
            """Call function to convert RGB image to grayscale image.

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

            Returns:
                dict: Result dict with grayscale image.
            """
            img = results['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)

            results['img'] = img
            results['img_shape'] = img.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

    @PIPELINES.register_module()
    class AdjustGamma(object):
        """Using gamma correction to process the image.

        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 __call__(self, results):
            """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(results['img'], dtype=np.uint8), self.table)

            return results

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

    @PIPELINES.register_module()
    class SegRescale(object):
        """Rescale semantic segmentation maps.

        Args:
            scale_factor (float): The scale factor of the final output.
        """

        def __init__(self, scale_factor=1):
            self.scale_factor = scale_factor

        def __call__(self, results):
            """Call function to scale the semantic segmentation map.

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

            Returns:
                dict: Result dict with semantic segmentation map scaled.
            """
            for key in results.get('seg_fields', []):
                if self.scale_factor != 1:
                    results[key] = mmcv.imrescale(
                        results[key], self.scale_factor, interpolation='nearest')
            return results

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

    @PIPELINES.register_module()
    class PhotoMetricDistortion(object):
        """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)
        8. randomly swap channels

        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.
        """

        def __init__(self,
                     brightness_delta=32,
                     contrast_range=(0.5, 1.5),
                     saturation_range=(0.5, 1.5),
                     hue_delta=18):
            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

        def convert(self, img, alpha=1, beta=0):
            """Multiple with alpha and add beat with clip."""
            img = img.astype(np.float32) * alpha + beta
            img = np.clip(img, 0, 255)
            return img.astype(np.uint8)

        def brightness(self, img):
            """Brightness distortion."""
            if random.randint(2):
                return self.convert(
                    img,
                    beta=random.uniform(-self.brightness_delta,
                                        self.brightness_delta))
            return img

        def contrast(self, img):
            """Contrast distortion."""
            if random.randint(2):
                return self.convert(
                    img,
                    alpha=random.uniform(self.contrast_lower, self.contrast_upper))
            return img

        def saturation(self, img):
            """Saturation distortion."""
            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):
            """Hue distortion."""
            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 __call__(self, results):
            """Call function to perform photometric distortion on images.

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

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

            img = results['img']
            # random brightness
            img = self.brightness(img)

            # mode == 0 --> do random contrast first
            # mode == 1 --> do random contrast last
            mode = 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)

            results['img'] = 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})')
            return repr_str