Source code for astroimtools.utils

# Licensed under a 3-clause BSD style license - see LICENSE.rst
Misc utility functions.
import warnings

import numpy as np
from astropy.coordinates import SkyCoord
from astropy.nddata import NDData, support_nddata
from astropy.nddata.utils import overlap_slices, Cutout2D
from astropy.table import Table
from astropy.utils.exceptions import AstropyUserWarning
from astropy.wcs.utils import skycoord_to_pixel

__all__ = ['radial_distance', 'listpixels', 'mask_databounds',

warnings.filterwarnings('always', category=AstropyUserWarning)

[docs]def radial_distance(position, shape): """ Return an array where each value is the Euclidean distance from a given position. Parameters ---------- position : tuple An ``(x, y)`` tuple of pixel coordinates for the central position (i.e., zero radial distance). shape : tuple The size of the output array along each axis. Returns ------- result : `~numpy.ndarray` An array containing the Euclidian radial distances from the input ``position``. Examples -------- >>> from astroimtools import radial_distance >>> radial_distance((1, 1), (3, 3)) # doctest: +FLOAT_CMP array([[1.41421356, 1. , 1.41421356], [1. , 0. , 1. ], [1.41421356, 1. , 1.41421356]]) """ if len(position) != 2: raise ValueError('position must have only 2 elements') if len(shape) != 2: raise ValueError('shape must have only 2 elements') x = np.arange(shape[1]) - position[1] y = np.arange(shape[0]) - position[0] xx, yy = np.meshgrid(x, y) return np.sqrt(xx**2 + yy**2)
[docs]@support_nddata def listpixels(data, position, shape, subarray_indices=False, wcs=None): """ Return a `~astropy.table.Table` listing the ``(y, x)`` positions and ``data`` values for a subarray. Given a position of the center of the subarray, with respect to the large array, the array indices and values are returned. This function takes care of the correct behavior at the boundaries, where the small array is appropriately trimmed. Parameters ---------- data : array-like The input data. position : tuple (int) or `~astropy.coordinates.SkyCoord` The position of the subarray center with respect to the data array. The position can be specified either as an integer ``(y, x)`` tuple of pixel coordinates or a `~astropy.coordinates.SkyCoord`, in which case ``wcs`` is a required input. shape : tuple (int) The integer shape (``(ny, nx)``) of the subarray. subarray_indices : bool, optional If `True` then the returned positions are relative to the small subarray. If `False` (default) then the returned positions are relative to the ``data`` array. wcs : `~astropy.wcs.WCS`, optional The WCS transformation to use if ``position`` is a `~astropy.coordinates.SkyCoord`. Returns ------- table : `~astropy.table.Table` A table containing the ``x`` and ``y`` positions and data values. Notes ----- This function is decorated with `~astropy.nddata.support_nddata` and thus supports `~astropy.nddata.NDData` objects as input. Examples -------- >>> import numpy as np >>> from astroimtools import listpixels >>> np.random.seed(12345) >>> data = np.random.random((25, 25)) >>> tbl = listpixels(data, (8, 11), (3, 3)) >>> for col in tbl.colnames: ... tbl[col].info.format = '%.8g' # for consistent table output >>> tbl.pprint(max_lines=-1) x y value --- --- ----------- 10 7 0.75857204 11 7 0.069529666 12 7 0.70547344 10 8 0.8406625 11 8 0.46931469 12 8 0.56264343 10 9 0.034131584 11 9 0.23049655 12 9 0.22835371 """ if isinstance(position, SkyCoord): if wcs is None: raise ValueError('wcs must be input if positions is a SkyCoord') x, y = skycoord_to_pixel(position, wcs, mode='all') position = (y, x) data = np.asanyarray(data) slices_large, slices_small = overlap_slices(data.shape, shape, position) slices = slices_large yy, xx = np.mgrid[slices] values = data[yy, xx] if subarray_indices: slices = slices_small yy, xx = np.mgrid[slices] tbl = Table() tbl['x'] = xx.ravel() tbl['y'] = yy.ravel() tbl['value'] = values.ravel() return tbl
[docs]@support_nddata def mask_databounds(data, mask=None, lower_bound=None, upper_bound=None, value=None, mask_invalid=True): """ Create or update a mask by masking data values that are below a lower bound, above an upper bound, equal to particular value, or are invalid (e.g. np.nan or np.inf). Parameters ---------- data : `~numpy.ndarray` The data array. mask : bool `~numpy.ndarray`, optional A boolean mask array with the same shape as ``data``. lower_bound : float, optional The value of the lower bound. Data values lower than ``lower_bound`` will be masked. upper_bound : float, optional The value of the upper bound. Data values greater than ``upper_bound`` will be masked. value : float, optional A data value (e.g., ``0.0``) to mask. mask_invalid : bool, optional If `True` (the default), then any unmasked invalid values (e.g. NaN, inf) will be masked. Returns ------- mask : bool `~numpy.ndarray` The resulting boolean mask array with the same shape as ``data``. Examples -------- >>> from astroimtools import mask_databounds >>> data = np.arange(7) >>> print(data) [0 1 2 3 4 5 6] >>> mask_databounds(data, lower_bound=2, upper_bound=5, value=3) array([ True, True, False, True, False, False, True]...) """ if mask is None: data =, mask=None) else: mask = np.asanyarray(mask) if mask.shape != data.shape: raise ValueError('mask and data must have the same shape') data =, mask=mask) if lower_bound is not None: data =, lower_bound) if upper_bound is not None: data =, upper_bound) if value is not None: data =, value) if mask_invalid: data = # mask np.nan, np.inf if np.all(data.mask): raise ValueError('All data values are masked') return data.mask
[docs]def nddata_cutout2d(nddata, position, size, mode='trim', fill_value=np.nan): """ Create a 2D cutout of a `~astropy.nddata.NDData` object. Specifically, cutouts will made for the ```` and ``nddata.mask`` (if present) arrays. If ``nddata.wcs`` exists, then it will also be updated. Note that cutouts will not be made for ``nddata.uncertainty`` (if present) because they are general objects and not arrays. Parameters ---------- nddata : `~astropy.nddata.NDData` The 2D `~astropy.nddata.NDData` from which the cutout is taken. position : tuple or `~astropy.coordinates.SkyCoord` The position of the cutout array's center with respect to the ```` array. The position can be specified either as a ``(x, y)`` tuple of pixel coordinates or a `~astropy.coordinates.SkyCoord`, in which case ``nddata.wcs`` must exist. size : int, array-like, `~astropy.units.Quantity` The size of the cutout array along each axis. If ``size`` is a scalar number or a scalar `~astropy.units.Quantity`, then a square cutout of ``size`` will be created. If ``size`` has two elements, they should be in ``(ny, nx)`` order. Scalar numbers in ``size`` are assumed to be in units of pixels. ``size`` can also be a `~astropy.units.Quantity` object or contain `~astropy.units.Quantity` objects. Such `~astropy.units.Quantity` objects must be in pixel or angular units. For all cases, ``size`` will be converted to an integer number of pixels, rounding the the nearest integer. See the ``mode`` keyword for additional details on the final cutout size. mode : {'trim', 'partial', 'strict'}, optional The mode used for creating the cutout data array. For the ``'partial'`` and ``'trim'`` modes, a partial overlap of the cutout array and the input ```` array is sufficient. For the ``'strict'`` mode, the cutout array has to be fully contained within the ```` array, otherwise an `~astropy.nddata.utils.PartialOverlapError` is raised. In all modes, non-overlapping arrays will raise a `~astropy.nddata.utils.NoOverlapError`. In ``'partial'`` mode, positions in the cutout array that do not overlap with the ```` array will be filled with ``fill_value``. In ``'trim'`` mode only the overlapping elements are returned, thus the resulting cutout array may be smaller than the requested ``size``. fill_value : number, optional If ``mode='partial'``, the value to fill pixels in the cutout array that do not overlap with the input ````. ``fill_value`` must have the same ``dtype`` as the input ```` array. Returns ------- result : `~astropy.nddata.NDData` A `~astropy.nddata.NDData` object with cutouts for the data and mask, if input. Examples -------- >>> from astropy.nddata import NDData >>> import astropy.units as u >>> from astroimtools import nddata_cutout2d >>> data = np.random.random((500, 500)) >>> unit = u.electron / u.s >>> mask = (data > 0.7) >>> meta = {'exptime': 1234 * u.s} >>> nddata = NDData(data, mask=mask, unit=unit, meta=meta) >>> cutout = nddata_cutout2d(nddata, (100, 100), (10, 10)) >>> (10, 10) >>> cutout.mask.shape (10, 10) >>> cutout.unit Unit("electron / s") """ if not isinstance(nddata, NDData): raise TypeError('nddata input must be an NDData object') if isinstance(position, SkyCoord): if nddata.wcs is None: raise ValueError('nddata must contain WCS if the input ' 'position is a SkyCoord') position = skycoord_to_pixel(position, nddata.wcs, mode='all') data_cutout = Cutout2D(np.asanyarray(, position, size, wcs=nddata.wcs, mode=mode, fill_value=fill_value) # need to create a new NDData instead of copying/replacing nddata_out = NDData(, unit=nddata.unit, uncertainty=nddata.uncertainty, meta=nddata.meta) if nddata.wcs is not None: nddata_out.wcs = data_cutout.wcs if nddata.mask is not None: mask_cutout = Cutout2D(np.asanyarray(nddata.mask), position, size, mode=mode, fill_value=fill_value) nddata_out.mask = return nddata_out