Source code for kornia.filters.kernels

from typing import Tuple, List

import torch
import torch.nn as nn


def gaussian(window_size, sigma):
    def gauss_fcn(x):
        return -(x - window_size // 2) ** 2 / float(2 * sigma ** 2)

    gauss = torch.stack(
        [torch.exp(torch.tensor(gauss_fcn(x))) for x in range(window_size)]
    )
    return gauss / gauss.sum()


def laplacian_1d(window_size) -> torch.Tensor:
    r"""One could also use the Laplacian of Gaussian formula
        to design the filter.
    """

    filter_1d = torch.ones(window_size)
    filter_1d[window_size // 2] = 1 - window_size
    laplacian_1d: torch.Tensor = filter_1d
    return laplacian_1d


def get_box_kernel2d(kernel_size: Tuple[int, int]) -> torch.Tensor:
    r"""Utility function that returns a box filter."""
    kx: float = float(kernel_size[0])
    ky: float = float(kernel_size[1])
    scale: torch.Tensor = torch.tensor(1.) / torch.tensor([kx * ky])
    tmp_kernel: torch.Tensor = torch.ones(1, kernel_size[0], kernel_size[1])
    return scale.to(tmp_kernel.dtype) * tmp_kernel


def get_binary_kernel2d(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 get_sobel_kernel_3x3() -> torch.Tensor:
    """Utility function that returns a sobel kernel of 3x3"""
    return torch.tensor([
        [-1., 0., 1.],
        [-2., 0., 2.],
        [-1., 0., 1.],
    ])


def get_sobel_kernel_5x5_2nd_order() -> torch.Tensor:
    """Utility function that returns a 2nd order sobel kernel of 5x5"""
    return torch.tensor([
        [-1., 0., 2., 0., -1.],
        [-4., 0., 8., 0., -4.],
        [-6., 0., 12., 0., -6.],
        [-4., 0., 8., 0., -4.],
        [-1., 0., 2., 0., -1.]
    ])


def _get_sobel_kernel_5x5_2nd_order_xy() -> torch.Tensor:
    """Utility function that returns a 2nd order sobel kernel of 5x5"""
    return torch.tensor([
        [-1., -2., 0., 2., 1.],
        [-2., -4., 0., 4., 2.],
        [0., 0., 0., 0., 0.],
        [2., 4., 0., -4., -2.],
        [1., 2., 0., -2., -1.]
    ])


def get_diff_kernel_3x3() -> torch.Tensor:
    """Utility function that returns a sobel kernel of 3x3"""
    return torch.tensor([
        [-0., 0., 0.],
        [-1., 0., 1.],
        [-0., 0., 0.],
    ])


def get_sobel_kernel2d() -> torch.Tensor:
    kernel_x: torch.Tensor = get_sobel_kernel_3x3()
    kernel_y: torch.Tensor = kernel_x.transpose(0, 1)
    return torch.stack([kernel_x, kernel_y])


def get_diff_kernel2d() -> torch.Tensor:
    kernel_x: torch.Tensor = get_diff_kernel_3x3()
    kernel_y: torch.Tensor = kernel_x.transpose(0, 1)
    return torch.stack([kernel_x, kernel_y])


def get_sobel_kernel2d_2nd_order() -> torch.Tensor:
    gxx: torch.Tensor = get_sobel_kernel_5x5_2nd_order()
    gyy: torch.Tensor = gxx.transpose(0, 1)
    gxy: torch.Tensor = _get_sobel_kernel_5x5_2nd_order_xy()
    return torch.stack([gxx, gxy, gyy])


def get_diff_kernel2d_2nd_order() -> torch.Tensor:
    gxx: torch.Tensor = torch.tensor([
        [0., 0., 0.],
        [1., -2., 1.],
        [0., 0., 0.],
    ])
    gyy: torch.Tensor = gxx.transpose(0, 1)
    gxy: torch.Tensor = torch.tensor([
        [-1., 0., 1.],
        [0., 0., 0.],
        [1., 0., -1.],
    ])
    return torch.stack([gxx, gxy, gyy])


def get_spatial_gradient_kernel2d(mode: str, order: int) -> torch.Tensor:
    r"""Function that returns kernel for 1st or 2nd order image gradients,
    using one of the following operators: sobel, diff"""
    if mode not in ['sobel', 'diff']:
        raise TypeError("mode should be either sobel\
                         or diff. Got {}".format(mode))
    if order not in [1, 2]:
        raise TypeError("order should be either 1 or 2\
                         Got {}".format(order))
    if mode == 'sobel' and order == 1:
        kernel: torch.Tensor = get_sobel_kernel2d()
    elif mode == 'sobel' and order == 2:
        kernel = get_sobel_kernel2d_2nd_order()
    elif mode == 'diff' and order == 1:
        kernel = get_diff_kernel2d()
    elif mode == 'diff' and order == 2:
        kernel = get_diff_kernel2d_2nd_order()
    else:
        raise NotImplementedError("")
    return kernel


def get_gaussian_kernel1d(kernel_size: int, sigma: float) -> torch.Tensor:
    r"""Function that returns Gaussian filter coefficients.

    Args:
        kernel_size (int): filter size. It should be odd and positive.
        sigma (float): gaussian standard deviation.

    Returns:
        Tensor: 1D tensor with gaussian filter coefficients.

    Shape:
        - Output: :math:`(\text{kernel_size})`

    Examples::

        >>> kornia.image.get_gaussian_kernel(3, 2.5)
        tensor([0.3243, 0.3513, 0.3243])

        >>> kornia.image.get_gaussian_kernel(5, 1.5)
        tensor([0.1201, 0.2339, 0.2921, 0.2339, 0.1201])
    """
    if (not isinstance(kernel_size, int) or (kernel_size % 2 == 0) or (
            kernel_size <= 0)):
        raise TypeError(
            "kernel_size must be an odd positive integer. "
            "Got {}".format(kernel_size)
        )
    window_1d: torch.Tensor = gaussian(kernel_size, sigma)
    return window_1d


[docs]def get_gaussian_kernel2d( kernel_size: Tuple[int, int], sigma: Tuple[float, float]) -> torch.Tensor: r"""Function that returns Gaussian filter matrix coefficients. Args: kernel_size (Tuple[int, int]): filter sizes in the x and y direction. Sizes should be odd and positive. sigma (Tuple[int, int]): gaussian standard deviation in the x and y direction. Returns: Tensor: 2D tensor with gaussian filter matrix coefficients. Shape: - Output: :math:`(\text{kernel_size}_x, \text{kernel_size}_y)` Examples:: >>> kornia.image.get_gaussian_kernel2d((3, 3), (1.5, 1.5)) tensor([[0.0947, 0.1183, 0.0947], [0.1183, 0.1478, 0.1183], [0.0947, 0.1183, 0.0947]]) >>> kornia.image.get_gaussian_kernel2d((3, 5), (1.5, 1.5)) tensor([[0.0370, 0.0720, 0.0899, 0.0720, 0.0370], [0.0462, 0.0899, 0.1123, 0.0899, 0.0462], [0.0370, 0.0720, 0.0899, 0.0720, 0.0370]]) """ if not isinstance(kernel_size, tuple) or len(kernel_size) != 2: raise TypeError( "kernel_size must be a tuple of length two. Got {}".format( kernel_size ) ) if not isinstance(sigma, tuple) or len(sigma) != 2: raise TypeError( "sigma must be a tuple of length two. Got {}".format(sigma) ) ksize_x, ksize_y = kernel_size sigma_x, sigma_y = sigma kernel_x: torch.Tensor = get_gaussian_kernel1d(ksize_x, sigma_x) kernel_y: torch.Tensor = get_gaussian_kernel1d(ksize_y, sigma_y) kernel_2d: torch.Tensor = torch.matmul( kernel_x.unsqueeze(-1), kernel_y.unsqueeze(-1).t() ) return kernel_2d
def get_laplacian_kernel1d(kernel_size: int) -> torch.Tensor: r"""Function that returns the coefficients of a 1D Laplacian filter. Args: kernel_size (int): filter size. It should be odd and positive. Returns: Tensor (float): 1D tensor with laplacian filter coefficients. Shape: - Output: math:`(\text{kernel_size})` Examples:: >>> kornia.image.get_laplacian_kernel(3) tensor([ 1., -2., 1.]) >>> kornia.image.get_laplacian_kernel(5) tensor([ 1., 1., -4., 1., 1.]) """ if not isinstance(kernel_size, int) or kernel_size % 2 == 0 or \ kernel_size <= 0: raise TypeError("ksize must be an odd positive integer. Got {}" .format(kernel_size)) window_1d: torch.Tensor = laplacian_1d(kernel_size) return window_1d
[docs]def get_laplacian_kernel2d(kernel_size: int) -> torch.Tensor: r"""Function that returns Gaussian filter matrix coefficients. Args: kernel_size (int): filter size should be odd. Returns: Tensor: 2D tensor with laplacian filter matrix coefficients. Shape: - Output: :math:`(\text{kernel_size}_x, \text{kernel_size}_y)` Examples:: >>> kornia.image.get_laplacian_kernel2d(3) tensor([[ 1., 1., 1.], [ 1., -8., 1.], [ 1., 1., 1.]]) >>> kornia.image.get_laplacian_kernel2d(5) tensor([[ 1., 1., 1., 1., 1.], [ 1., 1., 1., 1., 1.], [ 1., 1., -24., 1., 1.], [ 1., 1., 1., 1., 1.], [ 1., 1., 1., 1., 1.]]) """ if not isinstance(kernel_size, int) or kernel_size % 2 == 0 or \ kernel_size <= 0: raise TypeError("ksize must be an odd positive integer. Got {}" .format(kernel_size)) kernel = torch.ones((kernel_size, kernel_size)) mid = kernel_size // 2 kernel[mid, mid] = 1 - kernel_size ** 2 kernel_2d: torch.Tensor = kernel return kernel_2d