Source code for kornia.contrib.extract_patches

from typing import Optional, Union, Tuple

import torch
import torch.nn as nn
import torch.nn.functional as F

from torch.nn.modules.utils import _pair


[docs]class ExtractTensorPatches(nn.Module): r"""Module that extract patches from tensors and stack them. Applies a 2D convolution over an input tensor to extract patches and stack them in the depth axis of the output tensor. The function applies a Depthwise Convolution by applying the same kernel for all the input planes. In the simplest case, the output value of the operator with input size :math:`(B, C, H, W)` is :math:`(B, N, C, H_{out}, W_{out})`. where - :math:`B` is the batch size. - :math:`N` denotes the total number of extracted patches stacked in - :math:`C` denotes the number of input channels. - :math:`H`, :math:`W` the input height and width of the input in pixels. - :math:`H_{out}`, :math:`W_{out}` denote to denote to the patch size defined in the function signature. left-right and top-bottom order. * :attr:`window_size` is the size of the sliding window and controls the shape of the output tensor and defines the shape of the output patch. * :attr:`stride` controls the stride to apply to the sliding window and regulates the overlapping between the extracted patches. * :attr:`padding` controls the amount of implicit zeros-paddings on both sizes at each dimension. The parameters :attr:`window_size`, :attr:`stride` and :attr:`padding` can be either: - a single ``int`` -- in which case the same value is used for the height and width dimension. - a ``tuple`` of two ints -- in which case, the first `int` is used for the height dimension, and the second `int` for the width dimension. Arguments: window_size (Union[int, Tuple[int, int]]): the size of the convolving kernel and the output patch size. stride (Optional[Union[int, Tuple[int, int]]]): stride of the convolution. Default is 1. padding (Optional[Union[int, Tuple[int, int]]]): Zero-padding added to both side of the input. Default is 0. Shape: - Input: :math:`(B, C, H, W)` - Output: :math:`(B, N, C, H_{out}, W_{out})` Returns: torch.Tensor: the tensor with the extracted patches. Examples: >>> input = torch.arange(9.).view(1, 1, 3, 3) >>> patches = kornia.contrib.extract_tensor_patches(input, (2, 3)) >>> input tensor([[[[0., 1., 2.], [3., 4., 5.], [6., 7., 8.]]]]) >>> patches[:, -1] tensor([[[[3.0000, 4.0000, 5.0000], [6.0000, 7.0000, 8.0000]]]]) """ def __init__( self, window_size: Union[int, Tuple[int, int]], stride: Optional[Union[int, Tuple[int, int]]] = 1, padding: Optional[Union[int, Tuple[int, int]]] = 0) -> None: super(ExtractTensorPatches, self).__init__() self.window_size: Tuple[int, int] = _pair(window_size) self.stride: Tuple[int, int] = _pair(stride) self.padding: Tuple[int, int] = _pair(padding) # create base kernel self.kernel: torch.Tensor = self.create_kernel(self.window_size) @staticmethod def create_kernel( window_size: Tuple[int, int]) -> torch.Tensor: r"""Creates a binary kernel to extract the patches. If the window size is HxW will create a (H*W)xHxW kernel. """ window_range: int = window_size[0] * window_size[1] kernel: torch.Tensor = torch.zeros(window_range, window_range) for i in range(window_range): kernel[i, i] += 1.0 return kernel.view(window_range, 1, window_size[0], window_size[1]) def forward(self, input: torch.Tensor) -> torch.Tensor: # type: ignore if not torch.is_tensor(input): raise TypeError("Input input type is not a torch.Tensor. Got {}" .format(type(input))) if not len(input.shape) == 4: raise ValueError("Invalid input shape, we expect BxCxHxW. Got: {}" .format(input.shape)) # unpack shapes batch_size, channels, height, width = input.shape # run convolution 2d to extract patches kernel: torch.Tensor = self.kernel.repeat(channels, 1, 1, 1) kernel = kernel.to(input.device).to(input.dtype) output_tmp: torch.Tensor = F.conv2d( input, kernel, stride=self.stride, padding=self.padding, groups=channels) # reshape the output tensor output: torch.Tensor = output_tmp.view( batch_size, channels, self.window_size[0], self.window_size[1], -1) return output.permute(0, 4, 1, 2, 3) # BxNxCxhxw
###################### # functional interface ######################
[docs]def extract_tensor_patches( input: torch.Tensor, window_size: Union[int, Tuple[int, int]], stride: Optional[Union[int, Tuple[int, int]]] = 1, padding: Optional[Union[int, Tuple[int, int]]] = 0) -> torch.Tensor: r"""Function that extract patches from tensors and stack them. See :class:`~kornia.contrib.ExtractTensorPatches` for details. """ return ExtractTensorPatches(window_size, stride, padding)(input)