transform.py

import random
import warnings
from dataclasses import asdict, dataclass
from typing import Any, Dict, List, Optional, Sequence, Tuple, Union

import torch
import torchvision.transforms.functional as f
from torchvision.transforms import (
    CenterCrop,
    ColorJitter,
    Compose,
    Grayscale,
    InterpolationMode,
    Normalize,
    RandomResizedCrop,
    Resize,
    ToTensor,
)
from transformers.image_utils import OPENAI_CLIP_MEAN, OPENAI_CLIP_STD

OPENAI_DATASET_MEAN = tuple(OPENAI_CLIP_MEAN)
OPENAI_DATASET_STD = tuple(OPENAI_CLIP_STD)


def _setup_size(size, error_msg):
    if isinstance(size, int):
        return size, size
    if isinstance(size, Sequence) and len(size) == 1:
        return size[0], size[0]
    if len(size) != 2:
        raise ValueError(error_msg)
    return size


def _center_crop_or_pad(
    img: torch.Tensor,
    output_size: Union[int, Tuple[int, ...], List[int]],
    fill: Union[int, Tuple[int]] = 0,
) -> torch.Tensor:
    """
    Center crops and/or pads the given image. If the image is torch Tensor, it is
    expected to have [..., H, W] shape, where ... means an arbitrary number of leading
    dimensions. If image size is smaller than output size along any edge, image is
    padded with 0 and then center cropped.
    """
    if isinstance(output_size, int):
        output_size = (output_size, output_size)
    elif isinstance(output_size, (tuple, list)) and len(output_size) == 1:
        output_size = (output_size[0], output_size[0])

    _, image_height, image_width = f.get_dimensions(img)
    crop_height, crop_width = output_size

    if crop_width > image_width or crop_height > image_height:
        padding_ltrb = [
            (crop_width - image_width) // 2 if crop_width > image_width else 0,
            (crop_height - image_height) // 2 if crop_height > image_height else 0,
            (crop_width - image_width + 1) // 2 if crop_width > image_width else 0,
            (crop_height - image_height + 1) // 2 if crop_height > image_height else 0,
        ]
        img = f.pad(img, padding_ltrb, fill=fill)
        _, image_height, image_width = f.get_dimensions(img)
        if crop_width == image_width and crop_height == image_height:
            return img

    crop_top = int(round((image_height - crop_height) / 2.0))
    crop_left = int(round((image_width - crop_width) / 2.0))
    return f.crop(img, crop_top, crop_left, crop_height, crop_width)


class _CenterCropOrPad(torch.nn.Module):
    """Crops the given image at the center.
    If the image is torch Tensor, it is expected
    to have [..., H, W] shape, where ... means an arbitrary number of leading
    dimensions. If image size is smaller than output size along any edge, image is
    padded with 0 and then center cropped.

    Args:
        size (sequence or int): Desired output size of the crop. If size is an
            int instead of sequence like (h, w), a square crop (size, size) is
            made. If provided a sequence of length 1, it will be interpreted as
            (size[0], size[0]).
    """

    def __init__(self, size, fill=0):
        super().__init__()
        self.size = _setup_size(
            size, error_msg='Please provide only two dimensions (h, w) for size.'
        )
        self.fill = fill

    def forward(self, img):
        """
        Args:
            img (PIL Image or Tensor): Image to be cropped.

        Returns:
            PIL Image or Tensor: Cropped image.
        """
        return _center_crop_or_pad(img, self.size, fill=self.fill)

    def __repr__(self) -> str:
        return f'{self.__class__.__name__}(size={self.size})'


def _convert_to_rgb(image):
    return image.convert('RGB')


class _ResizeKeepRatio:
    """Resize while keeping ratio. Copied from timm"""

    def __init__(
        self,
        size,
        longest=0.0,
        interpolation=InterpolationMode.BICUBIC,
        random_scale_prob=0.0,
        random_scale_range=(0.85, 1.05),
        random_aspect_prob=0.0,
        random_aspect_range=(0.9, 1.11),
    ):
        if isinstance(size, (list, tuple)):
            self.size = tuple(size)
        else:
            self.size = (size, size)
        self.interpolation = interpolation
        self.longest = float(longest)  # [0, 1] where 0 == shortest edge, 1 == longest
        self.random_scale_prob = random_scale_prob
        self.random_scale_range = random_scale_range
        self.random_aspect_prob = random_aspect_prob
        self.random_aspect_range = random_aspect_range

    @staticmethod
    def get_params(
        img,
        target_size,
        longest,
        random_scale_prob=0.0,
        random_scale_range=(0.85, 1.05),
        random_aspect_prob=0.0,
        random_aspect_range=(0.9, 1.11),
    ):
        """Get parameters"""
        source_size = img.size[::-1]  # h, w
        h, w = source_size
        target_h, target_w = target_size
        ratio_h = h / target_h
        ratio_w = w / target_w
        ratio = max(ratio_h, ratio_w) * longest + min(ratio_h, ratio_w) * (
            1.0 - longest
        )
        if random_scale_prob > 0 and random.random() < random_scale_prob:
            ratio_factor = random.uniform(random_scale_range[0], random_scale_range[1])
            ratio_factor = (ratio_factor, ratio_factor)
        else:
            ratio_factor = (1.0, 1.0)
        if random_aspect_prob > 0 and random.random() < random_aspect_prob:
            aspect_factor = random.uniform(
                random_aspect_range[0], random_aspect_range[1]
            )
            ratio_factor = (
                ratio_factor[0] / aspect_factor,
                ratio_factor[1] * aspect_factor,
            )
        return [
            round(x * factor / ratio) for x, factor in zip(source_size, ratio_factor)
        ]

    def __call__(self, img):
        """
        Args:
            img (PIL Image): Image to be cropped and resized.

        Returns:
            PIL Image: Resized, padded to at least target size, possibly
            cropped to exactly target size
        """
        size = self.get_params(
            img,
            self.size,
            self.longest,
            self.random_scale_prob,
            self.random_scale_range,
            self.random_aspect_prob,
            self.random_aspect_range,
        )
        img = f.resize(img, size, self.interpolation)
        return img

    def __repr__(self):
        format_string = self.__class__.__name__ + '(size={0}'.format(self.size)
        format_string += f', interpolation={self.interpolation})'
        format_string += f', longest={self.longest:.3f})'
        return format_string


class _ColorJitter(object):
    """Apply color jitter to the PIL image with a specified probability"""

    def __init__(self, brightness=0.0, contrast=0.0, saturation=0.0, hue=0.0, p=0.8):
        assert 0.0 <= p <= 1.0
        self.p = p
        self.transf = ColorJitter(
            brightness=brightness, contrast=contrast, saturation=saturation, hue=hue
        )

    def __call__(self, img):
        if random.random() < self.p:
            return self.transf(img)
        else:
            return img


class _GrayScale(object):
    """Apply gray scale to the PIL image with a specified probability"""

    def __init__(self, p=0.2):
        assert 0.0 <= p <= 1.0
        self.p = p
        self.transf = Grayscale(num_output_channels=3)

    def __call__(self, img):
        if random.random() < self.p:
            return self.transf(img)
        else:
            return img


@dataclass
class AugmentationCfg:
    scale: Tuple[float, float] = (0.9, 1.0)
    ratio: Optional[Tuple[float, float]] = None
    color_jitter: Optional[
        Union[float, Tuple[float, float, float], Tuple[float, float, float, float]]
    ] = None
    re_prob: Optional[float] = None
    re_count: Optional[int] = None
    use_timm: bool = False
    color_jitter_prob: float = None
    gray_scale_prob: float = None


def image_transform(
    image_size: Union[int, Tuple[int, int]],
    is_train: bool,
    mean: Optional[Tuple[float, ...]] = None,
    std: Optional[Tuple[float, ...]] = None,
    resize_mode: Optional[str] = None,
    interpolation: Optional[str] = None,
    fill_color: int = 0,
    aug_cfg: Optional[Union[Dict[str, Any], AugmentationCfg]] = None,
):
    mean = mean or OPENAI_DATASET_MEAN
    if not isinstance(mean, (list, tuple)):
        mean = (mean,) * 3

    std = std or OPENAI_DATASET_STD
    if not isinstance(std, (list, tuple)):
        std = (std,) * 3

    interpolation = interpolation or 'bicubic'
    assert interpolation in ['bicubic', 'bilinear', 'random']
    # NOTE random is ignored for interpolation_mode, so defaults to BICUBIC for
    # inference if set
    interpolation_mode = (
        InterpolationMode.BILINEAR
        if interpolation == 'bilinear'
        else InterpolationMode.BICUBIC
    )

    resize_mode = resize_mode or 'shortest'
    assert resize_mode in ('shortest', 'longest', 'squash')

    if isinstance(aug_cfg, dict):
        aug_cfg = AugmentationCfg(**aug_cfg)
    else:
        aug_cfg = aug_cfg or AugmentationCfg()

    normalize = Normalize(mean=mean, std=std)

    if is_train:
        aug_cfg_dict = {k: v for k, v in asdict(aug_cfg).items() if v is not None}
        use_timm = aug_cfg_dict.pop('use_timm', False)
        if use_timm:
            from timm.data import create_transform  # timm can still be optional

            if isinstance(image_size, (tuple, list)):
                assert len(image_size) >= 2
                input_size = (3,) + image_size[-2:]
            else:
                input_size = (3, image_size, image_size)

            aug_cfg_dict.setdefault('color_jitter', None)  # disable by default
            # drop extra non-timm items
            aug_cfg_dict.pop('color_jitter_prob', None)
            aug_cfg_dict.pop('gray_scale_prob', None)

            train_transform = create_transform(
                input_size=input_size,
                is_training=True,
                hflip=0.0,
                mean=mean,
                std=std,
                re_mode='pixel',
                interpolation=interpolation,
                **aug_cfg_dict,
            )
        else:
            train_transform = [
                RandomResizedCrop(
                    image_size,
                    scale=aug_cfg_dict.pop('scale'),
                    interpolation=InterpolationMode.BICUBIC,
                ),
                _convert_to_rgb,
            ]
            if aug_cfg.color_jitter_prob:
                assert (
                    aug_cfg.color_jitter is not None and len(aug_cfg.color_jitter) == 4
                )
                train_transform.extend(
                    [_ColorJitter(*aug_cfg.color_jitter, p=aug_cfg.color_jitter_prob)]
                )
            if aug_cfg.gray_scale_prob:
                train_transform.extend([_GrayScale(aug_cfg.gray_scale_prob)])
            train_transform.extend(
                [
                    ToTensor(),
                    normalize,
                ]
            )
            train_transform = Compose(train_transform)
            if aug_cfg_dict:
                warnings.warn(
                    f'Unused augmentation cfg items, specify `use_timm` to use '
                    f'({list(aug_cfg_dict.keys())}).'
                )
        return train_transform
    else:
        if resize_mode == 'longest':
            transforms = [
                _ResizeKeepRatio(
                    image_size, interpolation=interpolation_mode, longest=1
                ),
                _CenterCropOrPad(image_size, fill=fill_color),
            ]
        elif resize_mode == 'squash':
            if isinstance(image_size, int):
                image_size = (image_size, image_size)
            transforms = [
                Resize(image_size, interpolation=interpolation_mode),
            ]
        else:
            assert resize_mode == 'shortest'
            if not isinstance(image_size, (tuple, list)):
                image_size = (image_size, image_size)
            if image_size[0] == image_size[1]:
                # simple case, use torchvision built-in Resize w/ shortest edge mode
                # (scalar size arg)
                transforms = [Resize(image_size[0], interpolation=interpolation_mode)]
            else:
                # resize shortest edge to matching target dim for non-square target
                transforms = [_ResizeKeepRatio(image_size)]
            transforms += [CenterCrop(image_size)]

        transforms.extend(
            [
                _convert_to_rgb,
                ToTensor(),
                normalize,
            ]
        )
        return Compose(transforms)