videosys/datasets/image_transform.py

# Adapted from DiT

# This source code is licensed under the license found in the
# LICENSE file in the root directory of this source tree.
# --------------------------------------------------------
# References:
# DiT:      https://github.com/facebookresearch/DiT
# --------------------------------------------------------


import numpy as np
import torchvision.transforms as transforms
from PIL import Image


def center_crop_arr(pil_image, image_size):
    """
    Center cropping implementation from ADM.
    https://github.com/openai/guided-diffusion/blob/8fb3ad9197f16bbc40620447b2742e13458d2831/guided_diffusion/image_datasets.py#L126
    """
    while min(*pil_image.size) >= 2 * image_size:
        pil_image = pil_image.resize(tuple(x // 2 for x in pil_image.size), resample=Image.BOX)

    scale = image_size / min(*pil_image.size)
    pil_image = pil_image.resize(tuple(round(x * scale) for x in pil_image.size), resample=Image.BICUBIC)

    arr = np.array(pil_image)
    crop_y = (arr.shape[0] - image_size) // 2
    crop_x = (arr.shape[1] - image_size) // 2
    return Image.fromarray(arr[crop_y : crop_y + image_size, crop_x : crop_x + image_size])


def get_transforms_image(image_size=256):
    transform = transforms.Compose(
        [
            transforms.Lambda(lambda pil_image: center_crop_arr(pil_image, image_size)),
            transforms.RandomHorizontalFlip(),
            transforms.ToTensor(),
            transforms.Normalize(mean=[0.5, 0.5, 0.5], std=[0.5, 0.5, 0.5], inplace=True),
        ]
    )
    return transform