src/data/transforms/efficientdet_pytorch_transforms.py

# Copy from: https://github.com/rwightman/efficientdet-pytorch/blob/d43c9e34cd62d22b4205831bb735f6dd83b8e881/effdet/data/transforms.py
""" COCO transforms (quick and dirty)

Hacked together by Ross Wightman
"""
import random
import math
from copy import deepcopy

from PIL import Image
import numpy as np
import torch

IMAGENET_DEFAULT_MEAN = (0.485, 0.456, 0.406)
IMAGENET_DEFAULT_STD = (0.229, 0.224, 0.225)
IMAGENET_INCEPTION_MEAN = (0.5, 0.5, 0.5)
IMAGENET_INCEPTION_STD = (0.5, 0.5, 0.5)


class ImageToNumpy:
    def __call__(self, pil_img, annotations: dict):
        np_img = np.array(pil_img, dtype=np.uint8)
        if np_img.ndim < 3:
            np_img = np.expand_dims(np_img, axis=-1)
        np_img = np.moveaxis(np_img, 2, 0)  # HWC to CHW
        return np_img, annotations


class ImageToTensor:
    def __init__(self, dtype=torch.float32):
        self.dtype = dtype

    def __call__(self, pil_img, annotations: dict):
        np_img = np.array(pil_img, dtype=np.uint8)
        if np_img.ndim < 3:
            np_img = np.expand_dims(np_img, axis=-1)
        np_img = np.moveaxis(np_img, 2, 0)  # HWC to CHW
        return torch.from_numpy(np_img).to(dtype=self.dtype), annotations


def _pil_interp(method):
    if method == "bicubic":
        return Image.BICUBIC
    elif method == "lanczos":
        return Image.LANCZOS
    elif method == "hamming":
        return Image.HAMMING
    else:
        # default bilinear, do we want to allow nearest?
        return Image.BILINEAR


_RANDOM_INTERPOLATION = (Image.BILINEAR, Image.BICUBIC)


def clip_boxes_(boxes, img_size):
    height, width = img_size
    clip_upper = np.array([height, width] * 2, dtype=boxes.dtype)
    np.clip(boxes, 0, clip_upper, out=boxes)


def clip_boxes(boxes, img_size):
    clipped_boxes = boxes.copy()
    clip_boxes_(clipped_boxes, img_size)
    return clipped_boxes


def _size_tuple(size):
    if isinstance(size, int):
        return size, size
    else:
        assert len(size) == 2
        return size


class ResizePad:
    def __init__(self, target_size: int, interpolation: str = "bilinear", fill_color: tuple = (0, 0, 0)):
        self.target_size = _size_tuple(target_size)
        self.interpolation = interpolation
        self.fill_color = fill_color

    def __call__(self, img, anno: dict):
        width, height = img.size

        img_scale_y = self.target_size[0] / height
        img_scale_x = self.target_size[1] / width
        img_scale = min(img_scale_y, img_scale_x)
        scaled_h = int(height * img_scale)
        scaled_w = int(width * img_scale)

        new_img = Image.new("RGB", (self.target_size[1], self.target_size[0]), color=self.fill_color)
        interp_method = _pil_interp(self.interpolation)
        img = img.resize((scaled_w, scaled_h), interp_method)
        new_img.paste(img)  # pastes at 0,0 (upper-left corner)

        if "bbox" in anno:
            bbox = anno["bbox"]
            bbox[:, :4] *= img_scale
            bbox_bound = (min(scaled_h, self.target_size[0]), min(scaled_w, self.target_size[1]))
            clip_boxes_(bbox, bbox_bound)  # crop to bounds of target image or letter-box, whichever is smaller
            valid_indices = (bbox[:, :2] < bbox[:, 2:4]).all(axis=1)
            anno["bbox"] = bbox[valid_indices, :]
            anno["cls"] = anno["cls"][valid_indices]

        anno["img_scale"] = 1.0 / img_scale  # back to original

        return new_img, anno


class RandomResizePad:
    def __init__(
        self, target_size: int, scale: tuple = (0.1, 2.0), interpolation: str = "random", fill_color: tuple = (0, 0, 0)
    ):
        self.target_size = _size_tuple(target_size)
        self.scale = scale
        if interpolation == "random":
            self.interpolation = _RANDOM_INTERPOLATION
        else:
            self.interpolation = _pil_interp(interpolation)
        self.fill_color = fill_color

    def _get_params(self, img):
        # Select a random scale factor.
        scale_factor = random.uniform(*self.scale)
        scaled_target_height = scale_factor * self.target_size[0]
        scaled_target_width = scale_factor * self.target_size[1]

        # Recompute the accurate scale_factor using rounded scaled image size.
        width, height = img.size
        img_scale_y = scaled_target_height / height
        img_scale_x = scaled_target_width / width
        img_scale = min(img_scale_y, img_scale_x)

        # Select non-zero random offset (x, y) if scaled image is larger than target size
        scaled_h = int(height * img_scale)
        scaled_w = int(width * img_scale)
        offset_y = scaled_h - self.target_size[0]
        offset_x = scaled_w - self.target_size[1]
        offset_y = int(max(0.0, float(offset_y)) * random.uniform(0, 1))
        offset_x = int(max(0.0, float(offset_x)) * random.uniform(0, 1))
        return scaled_h, scaled_w, offset_y, offset_x, img_scale

    def __call__(self, img, anno: dict):
        scaled_h, scaled_w, offset_y, offset_x, img_scale = self._get_params(img)

        if isinstance(self.interpolation, (tuple, list)):
            interpolation = random.choice(self.interpolation)
        else:
            interpolation = self.interpolation
        img = img.resize((scaled_w, scaled_h), interpolation)
        right, lower = min(scaled_w, offset_x + self.target_size[1]), min(scaled_h, offset_y + self.target_size[0])
        img = img.crop((offset_x, offset_y, right, lower))
        new_img = Image.new("RGB", (self.target_size[1], self.target_size[0]), color=self.fill_color)
        new_img.paste(img)  # pastes at 0,0 (upper-left corner)

        if "bbox" in anno:
            bbox = anno["bbox"]  # for convenience, modifies in-place
            bbox[:, :4] *= img_scale
            box_offset = np.stack([offset_y, offset_x] * 2)
            bbox -= box_offset
            bbox_bound = (min(scaled_h, self.target_size[0]), min(scaled_w, self.target_size[1]))
            clip_boxes_(bbox, bbox_bound)  # crop to bounds of target image or letter-box, whichever is smaller
            valid_indices = (bbox[:, :2] < bbox[:, 2:4]).all(axis=1)
            anno["bbox"] = bbox[valid_indices, :]
            anno["cls"] = anno["cls"][valid_indices]

        anno["img_scale"] = 1.0 / img_scale  # back to original

        return new_img, anno


class RandomFlip:
    def __init__(self, horizontal=True, vertical=False, prob=0.5):
        self.horizontal = horizontal
        self.vertical = vertical
        self.prob = prob

    def _get_params(self):
        do_horizontal = random.random() < self.prob if self.horizontal else False
        do_vertical = random.random() < self.prob if self.vertical else False
        return do_horizontal, do_vertical

    def __call__(self, img, annotations: dict):
        do_horizontal, do_vertical = self._get_params()
        width, height = img.size

        def _fliph(bbox):
            x_max = width - bbox[:, 1]
            x_min = width - bbox[:, 3]
            bbox[:, 1] = x_min
            bbox[:, 3] = x_max

        def _flipv(bbox):
            y_max = height - bbox[:, 0]
            y_min = height - bbox[:, 2]
            bbox[:, 0] = y_min
            bbox[:, 2] = y_max

        if do_horizontal and do_vertical:
            img = img.transpose(Image.ROTATE_180)
            if "bbox" in annotations:
                _fliph(annotations["bbox"])
                _flipv(annotations["bbox"])
        elif do_horizontal:
            img = img.transpose(Image.FLIP_LEFT_RIGHT)
            if "bbox" in annotations:
                _fliph(annotations["bbox"])
        elif do_vertical:
            img = img.transpose(Image.FLIP_TOP_BOTTOM)
            if "bbox" in annotations:
                _flipv(annotations["bbox"])

        return img, annotations


def resolve_fill_color(fill_color, img_mean=IMAGENET_DEFAULT_MEAN):
    if isinstance(fill_color, tuple):
        assert len(fill_color) == 3
        fill_color = fill_color
    else:
        try:
            int_color = int(fill_color)
            fill_color = (int_color,) * 3
        except ValueError:
            assert fill_color == "mean"
            fill_color = tuple([int(round(255 * x)) for x in img_mean])
    return fill_color


class Compose:
    def __init__(self, transforms: list):
        self.transforms = transforms

    def __call__(self, img, annotations: dict):
        for t in self.transforms:
            img, annotations = t(img, annotations)
        return img, annotations


def transforms_coco_eval(
    img_size=224,
    interpolation="bilinear",
    use_prefetcher=False,
    fill_color="mean",
    mean=IMAGENET_DEFAULT_MEAN,
    std=IMAGENET_DEFAULT_STD,
):
    fill_color = resolve_fill_color(fill_color, mean)

    image_tfl = [
        ResizePad(target_size=img_size, interpolation=interpolation, fill_color=fill_color),
        ImageToNumpy(),
    ]

    assert use_prefetcher, "Only supporting prefetcher usage right now"

    image_tf = Compose(image_tfl)
    return image_tf


def transforms_coco_train(
    img_size=224,
    interpolation="random",
    use_prefetcher=False,
    fill_color="mean",
    mean=IMAGENET_DEFAULT_MEAN,
    std=IMAGENET_DEFAULT_STD,
):
    fill_color = resolve_fill_color(fill_color, mean)

    image_tfl = [
        RandomFlip(horizontal=True, prob=0.5),
        RandomResizePad(target_size=img_size, interpolation=interpolation, fill_color=fill_color),
        ImageToNumpy(),
    ]

    assert use_prefetcher, "Only supporting prefetcher usage right now"

    image_tf = Compose(image_tfl)
    return image_tf