BoundingBox

class photutils.aperture.BoundingBox(ixmin, ixmax, iymin, iymax)

Bases: object

A rectangular bounding box in integer (not float) pixel indices.

Parameters:

ixmin, ixmax, iymin, iymaxint

The bounding box pixel indices. Note that the upper values (iymax and ixmax) are exclusive as for normal slices in Python. The lower values (ixmin and iymin) must not be greater than the respective upper values (ixmax and iymax).

Examples

When constructing a BoundingBox, it’s better to use keyword arguments for readability:

>>> from photutils.aperture import BoundingBox
>>> bbox = BoundingBox(ixmin=1, ixmax=10, iymin=2, iymax=20)
>>> bbox
BoundingBox(ixmin=1, ixmax=10, iymin=2, iymax=20)

Sometimes it’s useful to check if two bounding boxes are the same:

>>> bbox == BoundingBox(ixmin=1, ixmax=10, iymin=2, iymax=20)
True
>>> bbox == BoundingBox(ixmin=7, ixmax=10, iymin=2, iymax=20)
False

The “center” and “shape” attributes can be useful when working with numpy arrays:

>>> bbox.center  # numpy order: (y, x)
(10.5, 5.0)
>>> bbox.shape  # numpy order: (y, x)
(18, 9)

The “extent” is useful when plotting the BoundingBox with matplotlib:

>>> bbox.extent  # matplotlib order: (xmin, xmax, ymin, ymax)
(0.5, 9.5, 1.5, 19.5)

Attributes Summary

center	The (y, x) center of the bounding box.
extent	The extent of the mask, defined as the (xmin, xmax, ymin, ymax) bounding box from the bottom-left corner of the lower- left pixel to the upper-right corner of the upper-right pixel.
shape	The (ny, nx) shape of the bounding box.

Methods Summary

as_artist(**kwargs)	Return a matplotlib.patches.Rectangle that represents the bounding box.
from_float(xmin, xmax, ymin, ymax)	Return the smallest bounding box that fully contains a given rectangle defined by float coordinate values.
get_overlap_slices(shape)	Get slices for the overlapping part of the bounding box and a 2D array.
intersection(other)	Return a BoundingBox representing the intersection of this BoundingBox with another BoundingBox.
plot([ax, origin])	Plot the BoundingBox on a matplotlib Axes instance.
to_aperture()	Convert the bounding box to a RectangularAperture.
union(other)	Return a BoundingBox representing the union of this BoundingBox with another BoundingBox.

Attributes Documentation

center

The (y, x) center of the bounding box.

extent

The extent of the mask, defined as the (xmin, xmax, ymin, ymax) bounding box from the bottom-left corner of the lower- left pixel to the upper-right corner of the upper-right pixel.

The upper edges here are the actual pixel positions of the edges, i.e., they are not “exclusive” indices used for python indexing. The extent is useful for plotting the bounding box using Matplotlib.

shape

The (ny, nx) shape of the bounding box.

Methods Documentation

as_artist(**kwargs)

Return a matplotlib.patches.Rectangle that represents the bounding box.

Parameters:

**kwargsdict, optional

Any keyword arguments accepted by matplotlib.patches.Patch.

Returns:

resultmatplotlib.patches.Rectangle

A matplotlib rectangular patch.

Examples

import matplotlib.pyplot as plt
import numpy as np
from photutils.aperture import BoundingBox

bbox = BoundingBox(2, 7, 3, 8)
fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
rng = np.random.default_rng(0)
ax.imshow(rng.random((10, 10)), origin='lower')
ax.add_patch(bbox.as_artist(facecolor='none', edgecolor='white',
             lw=2.0))

(Source code, png, hires.png, pdf, svg)

classmethod from_float(xmin, xmax, ymin, ymax)

Return the smallest bounding box that fully contains a given rectangle defined by float coordinate values.

Following the pixel index convention, an integer index corresponds to the center of a pixel and the pixel edges span from (index - 0.5) to (index + 0.5). For example, the pixel edge spans of the following pixels are:

• pixel 0: from -0.5 to 0.5

• pixel 1: from 0.5 to 1.5

• pixel 2: from 1.5 to 2.5

In addition, because BoundingBox upper limits are exclusive (by definition), 1 is added to the upper pixel edges. See examples below.

Parameters:

xmin, xmax, ymin, ymaxfloat

The floating-point coordinates defining a rectangle. The lower values (xmin and ymin) must not be greater than the respective upper values (xmax and ymax).

Returns:

bboxBoundingBox object

The minimal BoundingBox object fully containing the input rectangle coordinates.

Examples

>>> from photutils.aperture import BoundingBox
>>> BoundingBox.from_float(xmin=1.0, xmax=10.0, ymin=2.0, ymax=20.0)
BoundingBox(ixmin=1, ixmax=11, iymin=2, iymax=21)

>>> BoundingBox.from_float(xmin=1.4, xmax=10.4, ymin=1.6, ymax=10.6)
BoundingBox(ixmin=1, ixmax=11, iymin=2, iymax=12)

get_overlap_slices(shape)

Get slices for the overlapping part of the bounding box and a 2D array.

Parameters:

shape2-tuple of int

The shape of the 2D array.

Returns:

slices_largetuple of slices or None

A tuple of slice objects for each axis of the large array, such that large_array[slices_large] extracts the region of the large array that overlaps with the small array. None is returned if there is no overlap of the bounding box with the given image shape.

slices_smalltuple of slices or None

A tuple of slice objects for each axis of an array enclosed by the bounding box such that small_array[slices_small] extracts the region that is inside the large array. None is returned if there is no overlap of the bounding box with the given image shape.

intersection(other)

Return a BoundingBox representing the intersection of this BoundingBox with another BoundingBox.

Parameters:

otherBoundingBox

The BoundingBox to intersect with this one.

Returns:

resultBoundingBox

A BoundingBox representing the intersection of the input BoundingBox with this one.

plot(ax=None, origin=(0, 0), **kwargs)

Plot the BoundingBox on a matplotlib Axes instance.

Parameters:

axmatplotlib.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, optional

Any keyword arguments accepted by matplotlib.patches.Patch.

Returns:

patchmatplotlib.patches.Patch

The matplotlib patch object for the plotted bounding box. The patch can be used, for example, when adding a plot legend.

to_aperture()

Convert the bounding box to a RectangularAperture.

Returns:

apertureRectangularAperture

A rectangular aperture.

union(other)

Return a BoundingBox representing the union of this BoundingBox with another BoundingBox.

Parameters:

otherBoundingBox

The BoundingBox to join with this one.

Returns:

resultBoundingBox

A BoundingBox representing the union of the input BoundingBox with this one.