PixelAperture¶

class
photutils.
PixelAperture
[source]¶ Bases:
photutils.Aperture
Abstract base class for apertures defined in pixel coordinates.
Attributes Summary
bounding_boxes
A list of minimal bounding boxes ( BoundingBox
), one for each position, for the aperture.Methods Summary
area
()Return the exact area of the aperture shape. do_photometry
(data[, error, mask, method, …])Perform aperture photometry on the input data. mask_area
([method, subpixels])Return the area of the aperture(s) mask. plot
([origin, indices, ax, fill])Plot the aperture(s) on a matplotlib Axes
instance.to_mask
([method, subpixels])Return a list of ApertureMask
objects, one for each aperture position.to_sky
(wcs[, mode])Convert the aperture to a SkyAperture
object defined in celestial coordinates.Attributes Documentation

bounding_boxes
¶ A list of minimal bounding boxes (
BoundingBox
), one for each position, for the aperture.
Methods Documentation

area
()[source]¶ Return the exact area of the aperture shape.
Returns: area : float
The aperture area.

do_photometry
(data, error=None, mask=None, method=u'exact', subpixels=5, unit=None)[source]¶ Perform aperture photometry on the input data.
Parameters: data : array_like or
Quantity
instanceThe 2D array on which to perform photometry.
data
should be background subtracted.error : array_like or
Quantity
, optionalThe pixelwise Gaussian 1sigma errors of the input
data
.error
is assumed to include all sources of error, including the Poisson error of the sources (seecalc_total_error
) .error
must have the same shape as the inputdata
.mask : array_like (bool), optional
A boolean mask with the same shape as
data
where aTrue
value indicates the corresponding element ofdata
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 thesubpixels
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. Ifsubpixels=1
, this method is equivalent to'center'
. The returned mask will contain values between 0 and 1.
subpixels : int, optional
For the
'subpixel'
method, resample pixels by this factor in each dimension. That is, each pixel is divided intosubpixels ** 2
subpixels.unit :
UnitBase
object or str, optionalReturns: aperture_sums :
ndarray
orQuantity
The sums within each aperture.
aperture_sum_errs :
ndarray
orQuantity
The errors on the sums within each aperture.

mask_area
(method=u'exact', subpixels=5)[source]¶ Return the area of the aperture(s) mask.
For
method
other than'exact'
, this area will be less than the exact analytical area (e.g. thearea
method). Note that for these methods, the values can also differ because of fractional pixel positions.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 thesubpixels
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. Ifsubpixels=1
, this method is equivalent to'center'
. The returned mask will contain values between 0 and 1.
subpixels : int, optional
For the
'subpixel'
method, resample pixels by this factor in each dimension. That is, each pixel is divided intosubpixels ** 2
subpixels.Returns: area : float
A list of the mask area of the aperture(s).

plot
(origin=(0, 0), indices=None, ax=None, fill=False, **kwargs)[source]¶ Plot the aperture(s) on a matplotlib
Axes
instance.Parameters: origin : array_like, optional
The
(x, y)
position of the origin of the displayed image.indices : int or array of int, optional
The indices of the aperture(s) to plot.
ax :
matplotlib.axes.Axes
instance, optionalfill : bool, optional
Set whether to fill the aperture patch. The default is
False
.kwargs
Any keyword arguments accepted by
matplotlib.patches.Patch
.

to_mask
(method=u'exact', subpixels=5)[source]¶ Return a list of
ApertureMask
objects, one for each aperture position.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 thesubpixels
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. Ifsubpixels=1
, this method is equivalent to'center'
. The returned mask will contain values between 0 and 1.
subpixels : int, optional
For the
'subpixel'
method, resample pixels by this factor in each dimension. That is, each pixel is divided intosubpixels ** 2
subpixels.Returns: mask : list of
ApertureMask
A list of aperture mask objects.

to_sky
(wcs, mode=u'all')[source]¶ Convert the aperture to a
SkyAperture
object defined in celestial coordinates.Parameters: wcs :
WCS
objectThe world coordinate system (WCS) transformation to use.
mode : {‘all’, ‘wcs’}, optional
Whether to do the transformation including distortions (
'all'
; default) or including only the core WCS transformation ('wcs'
).Returns: aperture :
SkyAperture
objectA
SkyAperture
object.
