# PixelAperture¶

class photutils.aperture.PixelAperture[source]

Abstract base class for apertures defined in pixel coordinates.

Attributes Summary

 area Return the exact area of the aperture shape. bbox The minimal bounding box for the aperture. bounding_boxes Deprecated since version 0.7.

Methods Summary

 do_photometry(data[, error, mask, method, …]) Perform aperture photometry on the input data. plot([axes, origin]) Plot the aperture on a matplotlib Axes instance. to_mask([method, subpixels]) Return a mask for the aperture. to_sky(wcs) Convert the aperture to a SkyAperture object defined in celestial coordinates.

Attributes Documentation

area

Return the exact area of the aperture shape.

Returns
areafloat

The aperture area.

bbox

The minimal bounding box for the aperture.

If the aperture is scalar then a single BoundingBox is returned, otherwise a list of BoundingBox is returned.

bounding_boxes

Deprecated since version 0.7: The bounding_boxes function is deprecated and may be removed in a future version. Use bbox instead.

The minimal bounding box for the aperture.

Methods Documentation

do_photometry(data, error=None, mask=None, method='exact', subpixels=5)[source]

Perform aperture photometry on the input data.

Parameters
dataarray_like or Quantity instance

The 2D array on which to perform photometry. data should be background subtracted.

errorarray_like or Quantity, optional

The pixel-wise Gaussian 1-sigma errors of the input data. error is assumed to include all sources of error, including the Poisson error of the sources (see calc_total_error) . error must have the same shape as the input data.

A boolean mask with the same shape as data where a True value indicates the corresponding element of data is masked. Masked data are excluded from all calculations.

method{‘exact’, ‘center’, ‘subpixel’}, optional

The method used to determine the overlap of the aperture on the pixel grid. Not all options are available for all aperture types. Note that the more precise methods are generally slower. The following methods are available:

• 'exact' (default): The the exact fractional overlap of the aperture and each pixel is calculated. The returned mask will contain values between 0 and 1.

• 'center': A pixel is considered to be entirely in or out of the aperture depending on whether its center is in or out of the aperture. The returned mask will contain values only of 0 (out) and 1 (in).

• 'subpixel' A pixel is divided into subpixels (see the subpixels keyword), each of which are considered to be entirely in or out of the aperture depending on whether its center is in or out of the aperture. If subpixels=1, this method is equivalent to 'center'. The returned mask will contain values between 0 and 1.

subpixelsint, optional

For the 'subpixel' method, resample pixels by this factor in each dimension. That is, each pixel is divided into subpixels ** 2 subpixels.

Returns
aperture_sums

The sums within each aperture.

aperture_sum_errs

The errors on the sums within each aperture.

plot(axes=None, origin=0, 0, **kwargs)[source]

Plot the aperture on a matplotlib Axes instance.

Parameters
axesmatplotlib.axes.Axes or None, optional

The matplotlib axes on which to plot. If None, then the current Axes instance is used.

originarray_like, optional

The (x, y) position of the origin of the displayed image.

kwargsdict

Any keyword arguments accepted by matplotlib.patches.Patch.

Returns
patchlist of Patch

A list of matplotlib patches for the plotted aperture. The patches can be used, for example, when adding a plot legend.

abstract to_mask(method='exact', subpixels=5)[source]

Return a mask for the aperture.

Parameters
method{‘exact’, ‘center’, ‘subpixel’}, optional

The method used to determine the overlap of the aperture on the pixel grid. Not all options are available for all aperture types. Note that the more precise methods are generally slower. The following methods are available:

• 'exact' (default): The the exact fractional overlap of the aperture and each pixel is calculated. The returned mask will contain values between 0 and 1.

• 'center': A pixel is considered to be entirely in or out of the aperture depending on whether its center is in or out of the aperture. The returned mask will contain values only of 0 (out) and 1 (in).

• 'subpixel': A pixel is divided into subpixels (see the subpixels keyword), each of which are considered to be entirely in or out of the aperture depending on whether its center is in or out of the aperture. If subpixels=1, this method is equivalent to 'center'. The returned mask will contain values between 0 and 1.

subpixelsint, optional

For the 'subpixel' method, resample pixels by this factor in each dimension. That is, each pixel is divided into subpixels ** 2 subpixels.

Returns

A mask for the aperture. If the aperture is scalar then a single ApertureMask is returned, otherwise a list of ApertureMask is returned.

abstract to_sky(wcs)[source]

Convert the aperture to a SkyAperture object defined in celestial coordinates.

Parameters
wcsWCS object

A world coordinate system (WCS) transformation that supports the astropy shared interface for WCS (e.g., astropy.wcs.WCS, gwcs.wcs.WCS).

Returns
apertureSkyAperture object

A SkyAperture object.