kornia.geometry.warp

class HomographyWarper(height: int, width: int, mode: str = 'bilinear', padding_mode: str = 'zeros', normalized_coordinates: bool = True)

Warps image patches or tensors by homographies.

\[X_{dst} = H_{src}^{\{dst\}} * X_{src}\]

Parameters:

• height (int) – The height of the image to warp.
• width (int) – The width of the image to warp.
• mode (str) – interpolation mode to calculate output values ‘bilinear’ | ‘nearest’. Default: ‘bilinear’.
• padding_mode (str) – padding mode for outside grid values ‘zeros’ | ‘border’ | ‘reflection’. Default: ‘zeros’.
• normalized_coordinates (bool) – wether to use a grid with normalized coordinates.

forward(patch_src: torch.Tensor, dst_homo_src: torch.Tensor) → torch.Tensor

Warps an image or tensor from source into reference frame.

Parameters:

• patch_src (torch.Tensor) – The image or tensor to warp. Should be from source.
• dst_homo_src (torch.Tensor) – The homography or stack of homographies from source to destination. The homography assumes normalized coordinates [-1, 1].

Returns:

Patch sampled at locations from source to destination.

Return type:

torch.Tensor

Shape:

• Input: \((N, C, H, W)\) and \((N, 3, 3)\)
• Output: \((N, C, H, W)\)

Example

>>> input = torch.rand(1, 3, 32, 32)
>>> homography = torch.eye(3).view(1, 3, 3)
>>> warper = kornia.HomographyWarper(32, 32)
>>> output = warper(input, homography)  # NxCxHxW

warp_grid(dst_homo_src: torch.Tensor) → torch.Tensor

Computes the grid to warp the coordinates grid by an homography.

Parameters:dst_homo_src (torch.Tensor) – Homography or homographies (stacked) to transform all points in the grid. Shape of the homography has to be \((N, 3, 3)\). Returns:the transformed grid of shape \((N, H, W, 2)\). Return type:torch.Tensor

class DepthWarper(pinhole_dst: kornia.geometry.camera.pinhole.PinholeCamera, height: int, width: int, mode: str = 'bilinear', padding_mode: str = 'zeros')

Warps a patch by depth.

\[ \begin{align}\begin{aligned}P_{src}^{\{dst\}} = K_{dst} * T_{src}^{\{dst\}}\\\begin{split}I_{src} = \\omega(I_{dst}, P_{src}^{\{dst\}}, D_{src})\end{split}\end{aligned}\end{align} \]

Parameters:

• pinholes_dst (PinholeCamera) – the pinhole models for the destination frame.
• height (int) – the height of the image to warp.
• width (int) – the width of the image to warp.
• mode (str) – interpolation mode to calculate output values ‘bilinear’ | ‘nearest’. Default: ‘bilinear’.
• padding_mode (str) – padding mode for outside grid values ‘zeros’ | ‘border’ | ‘reflection’. Default: ‘zeros’.

compute_projection_matrix(pinhole_src: kornia.geometry.camera.pinhole.PinholeCamera) → kornia.geometry.warp.depth_warper.DepthWarper

Computes the projection matrix from the source to destinaion frame.

compute_subpixel_step() → torch.Tensor

This computes the required inverse depth step to achieve sub pixel accurate sampling of the depth cost volume, per camera.

Szeliski, Richard, and Daniel Scharstein. “Symmetric sub-pixel stereo matching.” European Conference on Computer Vision. Springer Berlin Heidelberg, 2002.

forward(depth_src: torch.Tensor, patch_dst: torch.Tensor) → torch.Tensor

Warps a tensor from destination frame to reference given the depth in the reference frame.

Parameters:

• depth_src (torch.Tensor) – the depth in the reference frame. The tensor must have a shape \((B, 1, H, W)\).
• patch_dst (torch.Tensor) – the patch in the destination frame. The tensor must have a shape \((B, C, H, W)\).

Returns:

the warped patch from destination frame to reference.

Return type:

torch.Tensor

Shape:

• Output: \((N, C, H, W)\) where C = number of channels.

Example

>>> # pinholes camera models
>>> pinhole_dst = kornia.PinholeCamera(...)
>>> pinhole_src = kornia.PinholeCamera(...)
>>> # create the depth warper, compute the projection matrix
>>> warper = kornia.DepthWarper(pinhole_dst, height, width)
>>> warper.compute_projection_matrix(pinhole_src)
>>> # warp the destionation frame to reference by depth
>>> depth_src = torch.ones(1, 1, 32, 32)  # Nx1xHxW
>>> image_dst = torch.rand(1, 3, 32, 32)  # NxCxHxW
>>> image_src = warper(depth_src, image_dst)  # NxCxHxW

warp_grid(depth_src: torch.Tensor) → torch.Tensor

Computes a grid for warping a given the depth from the reference pinhole camera.

The function compute_projection_matrix has to be called beforehand in order to have precomputed the relative projection matrices encoding the relative pose and the intrinsics between the reference and a non reference camera.

homography_warp(patch_src: torch.Tensor, dst_homo_src: torch.Tensor, dsize: Tuple[int, int], mode: str = 'bilinear', padding_mode: str = 'zeros') → torch.Tensor

Function that warps image patchs or tensors by homographies.

See HomographyWarper for details.

Parameters:

• patch_src (torch.Tensor) – The image or tensor to warp. Should be from source of shape \((N, C, H, W)\).
• dst_homo_src (torch.Tensor) – The homography or stack of homographies from source to destination of shape \((N, 3, 3)\).
• dsize (Tuple[int, int]) – The height and width of the image to warp.
• mode (str) – interpolation mode to calculate output values ‘bilinear’ | ‘nearest’. Default: ‘bilinear’.
• padding_mode (str) – padding mode for outside grid values ‘zeros’ | ‘border’ | ‘reflection’. Default: ‘zeros’.

Returns:

Patch sampled at locations from source to destination.

Return type:

torch.Tensor

Example

>>> input = torch.rand(1, 3, 32, 32)
>>> homography = torch.eye(3).view(1, 3, 3)
>>> output = kornia.homography_warp(input, homography, (32, 32))

depth_warp(pinhole_dst: kornia.geometry.camera.pinhole.PinholeCamera, pinhole_src: kornia.geometry.camera.pinhole.PinholeCamera, depth_src: torch.Tensor, patch_dst: torch.Tensor, height: int, width: int)

Function that warps a tensor from destination frame to reference given the depth in the reference frame.

See DepthWarper for details.

Example

>>> # pinholes camera models
>>> pinhole_dst = kornia.PinholeCamera(...)
>>> pinhole_src = kornia.PinholeCamera(...)
>>> # warp the destionation frame to reference by depth
>>> depth_src = torch.ones(1, 1, 32, 32)  # Nx1xHxW
>>> image_dst = torch.rand(1, 3, 32, 32)  # NxCxHxW
>>> image_src = kornia.depth_warp(pinhole_dst, pinhole_src,
>>>     depth_src, image_dst, height, width)  # NxCxHxW