Source code for kornia.augmentation._2d.geometric.resized_crop

from typing import Any, Dict, Optional, Tuple, Union, cast

from torch import Tensor

from kornia.augmentation import random_generator as rg
from kornia.augmentation._2d.geometric.base import GeometricAugmentationBase2D
from kornia.constants import Resample
from kornia.geometry.transform import crop_by_indices, crop_by_transform_mat, get_perspective_transform

[docs]class RandomResizedCrop(GeometricAugmentationBase2D): r"""Crop random patches in an image tensor and resizes to a given size. .. image:: _static/img/RandomResizedCrop.png Args: size: Desired output size (out_h, out_w) of each edge. Must be Tuple[int, int], then out_h = size[0], out_w = size[1]. scale: range of size of the origin size cropped. ratio: range of aspect ratio of the origin aspect ratio cropped. resample: the interpolation mode. return_transform: if ``True`` return the matrix describing the transformation applied to each input tensor. If ``False`` and the input is a tuple the applied transformation won't be concatenated. same_on_batch: apply the same transformation across the batch. align_corners: interpolation flag. keepdim: whether to keep the output shape the same as input (True) or broadcast it to the batch form (False). cropping_mode: The used algorithm to crop. ``slice`` will use advanced slicing to extract the tensor based on the sampled indices. ``resample`` will use `warp_affine` using the affine transformation to extract and resize at once. Use `slice` for efficiency, or `resample` for proper differentiability. Shape: - Input: :math:`(C, H, W)` or :math:`(B, C, H, W)`, Optional: :math:`(B, 3, 3)` - Output: :math:`(B, C, out_h, out_w)` Note: Input tensor must be float and normalized into [0, 1] for the best differentiability support. Additionally, this function accepts another transformation tensor (:math:`(B, 3, 3)`), then the applied transformation will be merged int to the input transformation tensor and returned. Example: >>> rng = torch.manual_seed(0) >>> inputs = torch.tensor([[[0., 1., 2.], ... [3., 4., 5.], ... [6., 7., 8.]]]) >>> aug = RandomResizedCrop(size=(3, 3), scale=(3., 3.), ratio=(2., 2.), p=1., cropping_mode="resample") >>> out = aug(inputs) >>> out tensor([[[[1.0000, 1.5000, 2.0000], [4.0000, 4.5000, 5.0000], [7.0000, 7.5000, 8.0000]]]]) >>> aug.inverse(out, padding_mode="border") tensor([[[[1., 1., 2.], [4., 4., 5.], [7., 7., 8.]]]]) To apply the exact augmenation again, you may take the advantage of the previous parameter state: >>> input = torch.randn(1, 3, 32, 32) >>> aug = RandomResizedCrop(size=(3, 3), scale=(3., 3.), ratio=(2., 2.), p=1., cropping_mode="resample") >>> (aug(input) == aug(input, params=aug._params)).all() tensor(True) """ def __init__( self, size: Tuple[int, int], scale: Union[Tensor, Tuple[float, float]] = (0.08, 1.0), ratio: Union[Tensor, Tuple[float, float]] = (3.0 / 4.0, 4.0 / 3.0), resample: Union[str, int, Resample] =, same_on_batch: bool = False, align_corners: bool = True, p: float = 1.0, keepdim: bool = False, cropping_mode: str = "slice", return_transform: Optional[bool] = None, ) -> None: # Since PyTorch does not support ragged tensor. So cropping function happens all the time. super().__init__( p=1.0, return_transform=return_transform, same_on_batch=same_on_batch, p_batch=p, keepdim=keepdim ) self._param_generator = cast(rg.ResizedCropGenerator, rg.ResizedCropGenerator(size, scale, ratio)) self.flags = dict( size=size, resample=Resample.get(resample), align_corners=align_corners, cropping_mode=cropping_mode, padding_mode="zeros", ) def compute_transformation(self, input: Tensor, params: Dict[str, Tensor], flags: Dict[str, Any]) -> Tensor: if flags["cropping_mode"] in ("resample", "slice"): transform: Tensor = get_perspective_transform(params["src"].to(input), params["dst"].to(input)) transform = transform.expand(input.shape[0], -1, -1) return transform raise NotImplementedError(f"Not supported type: {flags['cropping_mode']}.") def apply_transform( self, input: Tensor, params: Dict[str, Tensor], flags: Dict[str, Any], transform: Optional[Tensor] = None ) -> Tensor: if flags["cropping_mode"] == "resample": # uses bilinear interpolation to crop transform = cast(Tensor, transform) return crop_by_transform_mat( input, transform, flags["size"], mode=flags["resample"].name.lower(), padding_mode="zeros", align_corners=flags["align_corners"], ) if flags["cropping_mode"] == "slice": # uses advanced slicing to crop return crop_by_indices( input, params["src"], flags["size"], interpolation=flags["resample"].name.lower(), align_corners=flags["align_corners"], ) raise NotImplementedError(f"Not supported type: {flags['cropping_mode']}.") def inverse_transform( self, input: Tensor, flags: Dict[str, Any], transform: Optional[Tensor] = None, size: Optional[Tuple[int, int]] = None, ) -> Tensor: if flags["cropping_mode"] != "resample": raise NotImplementedError( f"`inverse` is only applicable for resample cropping mode. Got {flags['cropping_mode']}." ) size = cast(Tuple[int, int], size) transform = cast(Tensor, transform) return crop_by_transform_mat( input, transform[:, :2, :], size, flags["resample"].name.lower(), flags["padding_mode"], flags["align_corners"], )