SlicedLowLevelWCS¶

class astropy.wcs.wcsapi.SlicedLowLevelWCS(wcs, slices)[source]

A Low Level WCS wrapper which applies an array slice to a WCS.

This class does not modify the underlying WCS object and can therefore drop coupled dimensions as it stores which pixel and world dimensions have been sliced out (or modified) in the underlying WCS and returns the modified results on all the Low Level WCS methods.

Parameters
wcsBaseLowLevelWCS

The WCS to slice.

slices

A valid array slice to apply to the WCS.

Attributes Summary

 array_shape The shape of the data that the WCS applies to as a tuple of length pixel_n_dim in (row, column) order (the convention for arrays in Python). axis_correlation_matrix Returns an (world_n_dim, pixel_n_dim) matrix that indicates using booleans whether a given world coordinate depends on a given pixel coordinate. dropped_world_dimensions Information describing the dropped world dimensions. pixel_axis_names An iterable of strings describing the name for each pixel axis. pixel_bounds The bounds (in pixel coordinates) inside which the WCS is defined, as a list with pixel_n_dim (min, max) tuples. pixel_n_dim The number of axes in the pixel coordinate system. pixel_shape The shape of the data that the WCS applies to as a tuple of length pixel_n_dim in (x, y) order (where for an image, x is the horizontal coordinate and y is the vertical coordinate). serialized_classes Indicates whether Python objects are given in serialized form or as actual Python objects. world_axis_names An iterable of strings describing the name for each world axis. world_axis_object_classes A dictionary giving information on constructing high-level objects for the world coordinates. world_axis_object_components A list with world_n_dim elements giving information on constructing high-level objects for the world coordinates. world_axis_physical_types An iterable of strings describing the physical type for each world axis. world_axis_units An iterable of strings given the units of the world coordinates for each axis. world_n_dim The number of axes in the world coordinate system.

Methods Summary

 array_index_to_world_values(*index_arrays) Convert array indices to world coordinates. pixel_to_world_values(*pixel_arrays) Convert pixel coordinates to world coordinates. world_to_array_index_values(*world_arrays) Convert world coordinates to array indices. world_to_pixel_values(*world_arrays) Convert world coordinates to pixel coordinates.

Attributes Documentation

array_shape
axis_correlation_matrix
dropped_world_dimensions

Information describing the dropped world dimensions.

pixel_axis_names
pixel_bounds
pixel_n_dim
pixel_shape
serialized_classes
world_axis_names
world_axis_object_classes
world_axis_object_components
world_axis_physical_types
world_axis_units
world_n_dim

Methods Documentation

array_index_to_world_values(*index_arrays)

Convert array indices to world coordinates.

This is the same as pixel_to_world_values except that the indices should be given in (i, j) order, where for an image i is the row and j is the column (i.e. the opposite order to pixel_to_world_values).

If world_n_dim is 1, this method returns a single scalar or array, otherwise a tuple of scalars or arrays is returned.

pixel_to_world_values(*pixel_arrays)[source]

Convert pixel coordinates to world coordinates.

This method takes pixel_n_dim scalars or arrays as input, and pixel coordinates should be zero-based. Returns world_n_dim scalars or arrays in units given by world_axis_units. Note that pixel coordinates are assumed to be 0 at the center of the first pixel in each dimension. If a pixel is in a region where the WCS is not defined, NaN can be returned. The coordinates should be specified in the (x, y) order, where for an image, x is the horizontal coordinate and y is the vertical coordinate.

If world_n_dim is 1, this method returns a single scalar or array, otherwise a tuple of scalars or arrays is returned.

world_to_array_index_values(*world_arrays)

Convert world coordinates to array indices.

This is the same as world_to_pixel_values except that the indices should be returned in (i, j) order, where for an image i is the row and j is the column (i.e. the opposite order to pixel_to_world_values). The indices should be returned as rounded integers.

If pixel_n_dim is 1, this method returns a single scalar or array, otherwise a tuple of scalars or arrays is returned.

world_to_pixel_values(*world_arrays)[source]

Convert world coordinates to pixel coordinates.

This method takes world_n_dim scalars or arrays as input in units given by world_axis_units. Returns pixel_n_dim scalars or arrays. Note that pixel coordinates are assumed to be 0 at the center of the first pixel in each dimension. If a world coordinate does not have a matching pixel coordinate, NaN can be returned. The coordinates should be returned in the (x, y) order, where for an image, x is the horizontal coordinate and y is the vertical coordinate.

If pixel_n_dim is 1, this method returns a single scalar or array, otherwise a tuple of scalars or arrays is returned.