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| """ Random Erasing (Cutout) | |
| Originally inspired by impl at https://github.com/zhunzhong07/Random-Erasing, Apache 2.0 | |
| Copyright Zhun Zhong & Liang Zheng | |
| Hacked together by / Copyright 2020 Ross Wightman | |
| """ | |
| import random | |
| import math | |
| import torch | |
| def _get_pixels(per_pixel, rand_color, patch_size, dtype=torch.float32, device='cuda'): | |
| # NOTE I've seen CUDA illegal memory access errors being caused by the normal_() | |
| # paths, flip the order so normal is run on CPU if this becomes a problem | |
| # Issue has been fixed in master https://github.com/pytorch/pytorch/issues/19508 | |
| if per_pixel: | |
| return torch.empty(patch_size, dtype=dtype, device=device).normal_() | |
| elif rand_color: | |
| return torch.empty((patch_size[0], 1, 1), dtype=dtype, device=device).normal_() | |
| else: | |
| return torch.zeros((patch_size[0], 1, 1), dtype=dtype, device=device) | |
| class RandomErasing: | |
| """ Randomly selects a rectangle region in an image and erases its pixels. | |
| 'Random Erasing Data Augmentation' by Zhong et al. | |
| See https://arxiv.org/pdf/1708.04896.pdf | |
| This variant of RandomErasing is intended to be applied to either a batch | |
| or single image tensor after it has been normalized by dataset mean and std. | |
| Args: | |
| probability: Probability that the Random Erasing operation will be performed. | |
| min_area: Minimum percentage of erased area wrt input image area. | |
| max_area: Maximum percentage of erased area wrt input image area. | |
| min_aspect: Minimum aspect ratio of erased area. | |
| mode: pixel color mode, one of 'const', 'rand', or 'pixel' | |
| 'const' - erase block is constant color of 0 for all channels | |
| 'rand' - erase block is same per-channel random (normal) color | |
| 'pixel' - erase block is per-pixel random (normal) color | |
| max_count: maximum number of erasing blocks per image, area per box is scaled by count. | |
| per-image count is randomly chosen between 1 and this value. | |
| """ | |
| def __init__( | |
| self, | |
| probability=0.5, min_area=0.02, max_area=1/3, min_aspect=0.3, max_aspect=None, | |
| mode='const', min_count=1, max_count=None, num_splits=0, device='cuda'): | |
| self.probability = probability | |
| self.min_area = min_area | |
| self.max_area = max_area | |
| max_aspect = max_aspect or 1 / min_aspect | |
| self.log_aspect_ratio = (math.log(min_aspect), math.log(max_aspect)) | |
| self.min_count = min_count | |
| self.max_count = max_count or min_count | |
| self.num_splits = num_splits | |
| mode = mode.lower() | |
| self.rand_color = False | |
| self.per_pixel = False | |
| if mode == 'rand': | |
| self.rand_color = True # per block random normal | |
| elif mode == 'pixel': | |
| self.per_pixel = True # per pixel random normal | |
| else: | |
| assert not mode or mode == 'const' | |
| self.device = device | |
| def _erase(self, img, chan, img_h, img_w, dtype): | |
| if random.random() > self.probability: | |
| return | |
| area = img_h * img_w | |
| count = self.min_count if self.min_count == self.max_count else \ | |
| random.randint(self.min_count, self.max_count) | |
| for _ in range(count): | |
| for attempt in range(10): | |
| target_area = random.uniform(self.min_area, self.max_area) * area / count | |
| aspect_ratio = math.exp(random.uniform(*self.log_aspect_ratio)) | |
| h = int(round(math.sqrt(target_area * aspect_ratio))) | |
| w = int(round(math.sqrt(target_area / aspect_ratio))) | |
| if w < img_w and h < img_h: | |
| top = random.randint(0, img_h - h) | |
| left = random.randint(0, img_w - w) | |
| img[:, top:top + h, left:left + w] = _get_pixels( | |
| self.per_pixel, self.rand_color, (chan, h, w), | |
| dtype=dtype, device=self.device) | |
| break | |
| def __call__(self, input): | |
| if len(input.size()) == 3: | |
| self._erase(input, *input.size(), input.dtype) | |
| else: | |
| batch_size, chan, img_h, img_w = input.size() | |
| # skip first slice of batch if num_splits is set (for clean portion of samples) | |
| batch_start = batch_size // self.num_splits if self.num_splits > 1 else 0 | |
| for i in range(batch_start, batch_size): | |
| self._erase(input[i], chan, img_h, img_w, input.dtype) | |
| return input | |