Source code for mmagic.datasets.transforms.random_down_sampling
# Copyright (c) OpenMMLab. All rights reserved.
import math
import numpy as np
import torch
from mmcv import imresize
from mmcv.transforms import BaseTransform
from mmagic.registry import TRANSFORMS
@TRANSFORMS.register_module()
[docs]class RandomDownSampling(BaseTransform):
"""Generate LQ image from GT (and crop), which will randomly pick a scale.
Args:
scale_min (float): The minimum of upsampling scale, inclusive.
Default: 1.0.
scale_max (float): The maximum of upsampling scale, exclusive.
Default: 4.0.
patch_size (int): The cropped lr patch size.
Default: None, means no crop.
interpolation (str): Interpolation method, accepted values are
"nearest", "bilinear", "bicubic", "area", "lanczos" for 'cv2'
backend, "nearest", "bilinear", "bicubic", "box", "lanczos",
"hamming" for 'pillow' backend.
Default: "bicubic".
backend (str | None): The image resize backend type. Options are `cv2`,
`pillow`, `None`. If backend is None, the global imread_backend
specified by ``mmcv.use_backend()`` will be used.
Default: "pillow".
Scale will be picked in the range of [scale_min, scale_max).
"""
def __init__(self,
scale_min=1.0,
scale_max=4.0,
patch_size=None,
interpolation='bicubic',
backend='pillow'):
assert scale_max >= scale_min
self.scale_min = scale_min
self.scale_max = scale_max
self.patch_size = patch_size
self.interpolation = interpolation
self.backend = backend
[docs] def transform(self, results):
"""transform function.
Args:
results (dict): A dict containing the necessary information and
data for augmentation. 'gt' is required.
Returns:
dict: A dict containing the processed data and information.
modified 'gt', supplement 'lq' and 'scale' to keys.
"""
img = results['gt']
scale = np.random.uniform(self.scale_min, self.scale_max)
if self.patch_size is None:
h_lr = math.floor(img.shape[-3] / scale + 1e-9)
w_lr = math.floor(img.shape[-2] / scale + 1e-9)
img = img[:round(h_lr * scale), :round(w_lr * scale), :]
img_down = resize_fn(img, (w_lr, h_lr), self.interpolation,
self.backend)
crop_lr, crop_hr = img_down, img
else:
w_lr = self.patch_size
w_hr = round(w_lr * scale)
x0 = np.random.randint(0, img.shape[-3] - w_hr)
y0 = np.random.randint(0, img.shape[-2] - w_hr)
crop_hr = img[x0:x0 + w_hr, y0:y0 + w_hr, :]
crop_lr = resize_fn(crop_hr, w_lr, self.interpolation,
self.backend)
results['gt'] = crop_hr
results['img'] = crop_lr
results['scale'] = scale
# copy metainfo to lr image
if 'gt_channel_order' in results:
results['img_channel_order'] = results['gt_channel_order']
if 'gt_color_type' in results:
results['img_color_type'] = results['gt_color_type']
return results
[docs] def __repr__(self):
repr_str = self.__class__.__name__
repr_str += (f' scale_min={self.scale_min}, '
f'scale_max={self.scale_max}, '
f'patch_size={self.patch_size}, '
f'interpolation={self.interpolation}, '
f'backend={self.backend}')
return repr_str
[docs]def resize_fn(img, size, interpolation='bicubic', backend='pillow'):
"""Resize the given image to a given size.
Args:
img (np.ndarray | torch.Tensor): The input image.
size (int | tuple[int]): Target size w or (w, h).
interpolation (str): Interpolation method, accepted values are
"nearest", "bilinear", "bicubic", "area", "lanczos" for 'cv2'
backend, "nearest", "bilinear", "bicubic", "box", "lanczos",
"hamming" for 'pillow' backend.
Default: "bicubic".
backend (str | None): The image resize backend type. Options are `cv2`,
`pillow`, `None`. If backend is None, the global imread_backend
specified by ``mmcv.use_backend()`` will be used.
Default: "pillow".
Returns:
np.ndarray | Tensor: `resized_img`, whose type is same as `img`.
"""
if isinstance(size, int):
size = (size, size)
if isinstance(img, np.ndarray):
return imresize(
img, size, interpolation=interpolation, backend=backend)
elif isinstance(img, torch.Tensor):
image = imresize(
img.numpy(), size, interpolation=interpolation, backend=backend)
return torch.from_numpy(image)
else:
raise TypeError('img should got np.ndarray or torch.Tensor,'
f'but got {type(img)}')