| import numpy as np | |
| import torch | |
| from torchvision.transforms import Compose, Resize, ToTensor, CenterCrop, transforms | |
| class ExpandChannels: | |
| """ | |
| Transforms an image with one channel to an image with three channels by copying | |
| pixel intensities of the image along the 1st dimension. | |
| """ | |
| def __call__(self, data: torch.Tensor) -> torch.Tensor: | |
| """ | |
| :param data: Tensor of shape [1, H, W]. | |
| :return: Tensor with channel copied three times, shape [3, H, W]. | |
| """ | |
| if data.shape[0] != 1: | |
| raise ValueError(f"Expected input of shape [1, H, W], found {data.shape}") | |
| return torch.repeat_interleave(data, 3, dim=0) | |
| def create_chest_xray_transform_for_inference(resize: int, center_crop_size: int) -> Compose: | |
| """ | |
| Defines the image transformation pipeline for Chest-Xray datasets. | |
| :param resize: The size to resize the image to. Linear resampling is used. | |
| Resizing is applied on the axis with smaller shape. | |
| :param center_crop_size: The size to center crop the image to. Square crop is applied. | |
| """ | |
| transforms = [Resize(resize), CenterCrop(center_crop_size), ToTensor(), ExpandChannels()] | |
| return Compose(transforms) | |
| def remap_to_uint8(array: np.ndarray, percentiles=None) -> np.ndarray: | |
| """Remap values in input so the output range is :math:`[0, 255]`. | |
| Percentiles can be used to specify the range of values to remap. | |
| This is useful to discard outliers in the input data. | |
| :param array: Input array. | |
| :param percentiles: Percentiles of the input values that will be mapped to ``0`` and ``255``. | |
| Passing ``None`` is equivalent to using percentiles ``(0, 100)`` (but faster). | |
| :returns: Array with ``0`` and ``255`` as minimum and maximum values. | |
| """ | |
| array = array.astype(float) | |
| if percentiles is not None: | |
| len_percentiles = len(percentiles) | |
| if len_percentiles != 2: | |
| message = ( | |
| 'The value for percentiles should be a sequence of length 2,' | |
| f' but has length {len_percentiles}' | |
| ) | |
| raise ValueError(message) | |
| a, b = percentiles | |
| if a >= b: | |
| raise ValueError(f'Percentiles must be in ascending order, but a sequence "{percentiles}" was passed') | |
| if a < 0 or b > 100: | |
| raise ValueError(f'Percentiles must be in the range [0, 100], but a sequence "{percentiles}" was passed') | |
| cutoff: np.ndarray = np.percentile(array, percentiles) | |
| array = np.clip(array, *cutoff) | |
| array -= array.min() | |
| array /= array.max() | |
| array *= 255 | |
| return array.astype(np.uint8) | |