RectangularAperture#

class photutils.aperture.RectangularAperture(positions, w, h, theta=0.0)[source]#

Bases: PixelAperture

A rectangular aperture defined in pixel coordinates.

The aperture has a single fixed size/shape, but it can have multiple positions (see the positions input).

Parameters:

positionsarray_like

The pixel coordinates of the aperture center(s) in one of the following formats:

single (x, y) pair as a tuple, list, or ndarray
tuple, list, or ndarray of (x, y) pairs

wfloat

The full width of the rectangle in pixels. For theta=0 the width side is along the x axis.

hfloat

The full height of the rectangle in pixels. For theta=0 the height side is along the y axis.

thetafloat or Quantity, optional

The rotation angle as an angular quantity (Quantity or Angle) or value in radians (as a float) from the positive x axis. The rotation angle increases counterclockwise.

Raises:

ValueErrorValueError: If either width (w) or height (h) is negative.

Examples

>>> from astropy.coordinates import Angle
>>> from photutils.aperture import RectangularAperture

>>> theta = Angle(80, 'deg')
>>> aper = RectangularAperture([10.0, 20.0], 5.0, 3.0)
>>> aper = RectangularAperture((10.0, 20.0), 5.0, 3.0, theta=theta)

>>> pos1 = (10.0, 20.0)  # (x, y)
>>> pos2 = (30.0, 40.0)
>>> pos3 = (50.0, 60.0)
>>> aper = RectangularAperture([pos1, pos2, pos3], 5.0, 3.0)
>>> aper = RectangularAperture((pos1, pos2, pos3), 5.0, 3.0, theta=theta)

Attributes Summary

`area`	The exact geometric area of the aperture shape.
`bbox`	The minimal bounding box for the aperture.
`h`	The full height in pixels.
`isscalar`	Whether the instance is scalar (i.e., a single position).
`positions`	The center pixel position(s).
`shape`	The shape of the instance.
`theta`	The counterclockwise rotation angle as an angular Quantity or a value in radians from the positive x axis.
`w`	The full width in pixels.

Methods Summary

`area_overlap`(data, *[, mask, method, subpixels])	Return the area of overlap between the data and the aperture.
`copy`()	Make a deep copy of this object.
`do_photometry`(data[, error, mask, method, ...])	Perform aperture photometry on the input data.
`plot`([ax, 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 `SkyRectangularAperture` object defined in celestial coordinates.

Attributes Documentation

area#: The exact geometric area of the aperture shape.

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.

h#: The full height in pixels.

isscalar#: Whether the instance is scalar (i.e., a single position).

positions#: The center pixel position(s).

shape#: The shape of the instance.

theta#: The counterclockwise rotation angle as an angular Quantity or a value in radians from the positive x axis.

w#: The full width in pixels.

Methods Documentation

area_overlap(data, *, mask=None, method='exact', subpixels=5)#

Return the area of overlap between the data and the aperture.

This method takes into account the aperture mask method, masked data pixels (mask keyword), and partial/no overlap of the aperture with the data. In other words, it returns the area that used to compute the aperture sum (assuming identical inputs).

Use the area method to calculate the exact analytical area of the aperture shape.

Parameters:

dataarray_like or Quantity

A 2D array.

maskarray_like (bool), optional

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 the area overlap.

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

The method used to determine the pixel weights (the fraction of the pixel area covered by the aperture):

'exact' (default): Calculates the exact geometric overlap area. Weights are continuous in the range [0, 1].
'center': Binary weighting based on the pixel center. Weights are either 0 or 1.
'subpixel': Approximates the overlap by averaging binary samples on a subgrid. The number of samples is set by the subpixels parameter. Weights are discrete in the range [0, 1].

subpixelsint, optional

The subsampling factor per axis used when method='subpixel'. Each pixel is divided into a grid of subpixels**2 subpixels to approximate the overlap. This parameter is ignored for other methods.

Returns:

areasfloat or array_like: The area (in pixels**2) of overlap between the data and the aperture.