Spatial Distortion Index

Module Interface

class torchmetrics.image.SpatialDistortionIndex(norm_order=1, window_size=7, reduction='elementwise_mean', **kwargs)

Compute Spatial Distortion Index (SpatialDistortionIndex) also now as D_s.

The metric is used to compare the spatial distortion between two images. A value of 0 indicates no distortion (optimal value) and corresponds to the case where the high resolution panchromatic image is equal to the low resolution panchromatic image. The metric is defined as:

\[\begin{split}D_s = \\sqrt[q]{\frac{1}{L}\\sum_{l=1}^L|Q(\\hat{G_l}, P) - Q(\tilde{G}, \tilde{P})|^q}\end{split}\]

where \(Q\) is the universal image quality index (see this UniversalImageQualityIndex for more info), \(\\hat{G_l}\) is the l-th band of the high resolution multispectral image, \(\tilde{G}\) is the high resolution panchromatic image, \(P\) is the high resolution panchromatic image, \(\tilde{P}\) is the low resolution panchromatic image, \(L\) is the number of bands and \(q\) is the order of the norm applied on the difference.

As input to forward and update the metric accepts the following input

• preds (Tensor): High resolution multispectral image of shape (N,C,H,W).

• target (Dict): A dictionary containing the following keys:

  • ms (Tensor): Low resolution multispectral image of shape (N,C,H',W').

  • pan (Tensor): High resolution panchromatic image of shape (N,C,H,W).

  • pan_lr (Tensor): Low resolution panchromatic image of shape (N,C,H',W').

where H and W must be multiple of H’ and W’.

As output of forward and compute the metric returns the following output

• sdi (Tensor): if reduction!='none' returns float scalar tensor with average SDI value over sample else returns tensor of shape (N,) with SDI values per sample

Parameters:

• norm_order (int) – Order of the norm applied on the difference.

• window_size (int) – Window size of the filter applied to degrade the high resolution panchromatic image.

• reduction (Literal['elementwise_mean', 'sum', 'none']) –

  a method to reduce metric score over labels.

  • 'elementwise_mean': takes the mean (default)

  • 'sum': takes the sum

  • 'none': no reduction will be applied

• kwargs (Any) – Additional keyword arguments, see Advanced metric settings for more info.

Example

>>> from torch import rand
>>> from torchmetrics.image import SpatialDistortionIndex
>>> preds = rand([16, 3, 32, 32])
>>> target = {
...     'ms': rand([16, 3, 16, 16]),
...     'pan': rand([16, 3, 32, 32]),
... }
>>> sdi = SpatialDistortionIndex()
>>> sdi(preds, target)
tensor(0.0090)

plot(val=None, ax=None)

Plot a single or multiple values from the metric.

Parameters:

• val (Union[Tensor, Sequence[Tensor], None]) – Either a single result from calling metric.forward or metric.compute or a list of these results. If no value is provided, will automatically call metric.compute and plot that result.

• ax (Optional[Axes]) – An matplotlib axis object. If provided will add plot to that axis

Return type:

Tuple[Figure, Union[Axes, ndarray]]

Returns:

Figure and Axes object

Raises:

ModuleNotFoundError – If matplotlib is not installed

>>> # Example plotting a single value
>>> from torch import rand
>>> from torchmetrics.image import SpatialDistortionIndex
>>> preds = rand([16, 3, 32, 32])
>>> target = {
...     'ms': rand([16, 3, 16, 16]),
...     'pan': rand([16, 3, 32, 32]),
... }
>>> metric = SpatialDistortionIndex()
>>> metric.update(preds, target)
>>> fig_, ax_ = metric.plot()

>>> # Example plotting multiple values
>>> from torch import rand
>>> from torchmetrics.image import SpatialDistortionIndex
>>> preds = rand([16, 3, 32, 32])
>>> target = {
...     'ms': rand([16, 3, 16, 16]),
...     'pan': rand([16, 3, 32, 32]),
... }
>>> metric = SpatialDistortionIndex()
>>> values = [ ]
>>> for _ in range(10):
...     values.append(metric(preds, target))
>>> fig_, ax_ = metric.plot(values)

Functional Interface

torchmetrics.functional.image.spatial_distortion_index(preds, ms, pan, pan_lr=None, norm_order=1, window_size=7, reduction='elementwise_mean')

Calculate Spatial Distortion Index (SpatialDistortionIndex) also known as D_s.

Metric is used to compare the spatial distortion between two images.

Parameters:

• preds (Tensor) – High resolution multispectral image.

• ms (Tensor) – Low resolution multispectral image.

• pan (Tensor) – High resolution panchromatic image.

• pan_lr (Optional[Tensor]) – Low resolution panchromatic image.

• norm_order (int) – Order of the norm applied on the difference.

• window_size (int) – Window size of the filter applied to degrade the high resolution panchromatic image.

• reduction (Literal['elementwise_mean', 'sum', 'none']) –

  A method to reduce metric score over labels.

  • 'elementwise_mean': takes the mean (default)

  • 'sum': takes the sum

  • 'none': no reduction will be applied

Return type:

Tensor

Returns:

Tensor with SpatialDistortionIndex score

Raises:

• TypeError – If preds, ms, pan and pan_lr don’t have the same data type.

• ValueError – If preds, ms, pan and pan_lr don’t have BxCxHxW shape.

• ValueError – If preds, ms, pan and pan_lr don’t have the same batch and channel sizes.

• ValueError – If preds and pan don’t have the same dimension.

• ValueError – If ms and pan_lr don’t have the same dimension.

• ValueError – If preds and pan don’t have dimension which is multiple of that of ms.

• ValueError – If norm_order is not a positive integer.

• ValueError – If window_size is not a positive integer.

Example

>>> from torch import rand
>>> from torchmetrics.functional.image import spatial_distortion_index
>>> preds = rand([16, 3, 32, 32])
>>> ms = rand([16, 3, 16, 16])
>>> pan = rand([16, 3, 32, 32])
>>> spatial_distortion_index(preds, ms, pan)
tensor(0.0090)