CircleAnnulusPixelRegion

class regions.CircleAnnulusPixelRegion(center, inner_radius, outer_radius, meta=None, visual=None)

Bases: AnnulusPixelRegion

A circular annulus in pixel coordinates.

Parameters:

centerPixCoord

The position of the center of the annulus.

inner_radiusfloat

The inner radius of the annulus in pixels.

outer_radiusfloat

The outer radius of the annulus in pixels.

metaRegionMeta or dict, optional

A dictionary that stores the meta attributes of the region.

visualRegionVisual or dict, optional

A dictionary that stores the visual meta attributes of the region.

Examples

from regions import PixCoord, CircleAnnulusPixelRegion
import matplotlib.pyplot as plt

fig, ax = plt.subplots(1, 1)

reg = CircleAnnulusPixelRegion(PixCoord(x=6, y=6),
                               inner_radius=5.5,
                               outer_radius=8.0)
patch = reg.plot(ax=ax, facecolor='none', edgecolor='red', lw=2,
                 label='Circle Annulus')

ax.legend(handles=(patch,), loc='upper center')
ax.set_xlim(-5, 20)
ax.set_ylim(-5, 20)
ax.set_aspect('equal')

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

Attributes Summary

center	The center pixel position as a PixCoord.
inner_radius	The inner radius in pixels as a float.
meta	The meta attributes as a RegionMeta
outer_radius	The outer radius in pixels as a float.
visual	The visual attributes as a RegionVisual.

Methods Summary

to_polygon([n_points])	Return a CompoundPixelRegion of two PolygonPixelRegion objects that approximates this annulus.
to_sky(wcs)	Return a region defined in sky coordinates.
to_spherical_sky([wcs, ...])	Convert to an equivalent spherical SphericalSkyRegion instance.

Attributes Documentation

center

The center pixel position as a PixCoord.

inner_radius

The inner radius in pixels as a float.

meta

The meta attributes as a RegionMeta

outer_radius

The outer radius in pixels as a float.

visual

The visual attributes as a RegionVisual.

Methods Documentation

to_polygon(n_points=100)

Return a CompoundPixelRegion of two PolygonPixelRegion objects that approximates this annulus.

Parameters:

n_pointsint, optional

The number of polygon vertices for each circle. Default is 100.

Returns:

polygonCompoundPixelRegion

A compound region of two polygon regions approximating the annulus.

to_sky(wcs)

Return a region defined in sky coordinates.

Parameters:

wcsWCS

The world coordinate system transformation to use to convert from pixels to sky coordinates.

Returns:

sky_regionSkyRegion

The sky region.

Notes

The conversion between pixel and sky coordinates is an approximation. The pixel region shape is mapped to a sky region shape using the local pixel scale and angle at the region center. Projection effects over the extent of the region are not accounted for. The region shape type is always preserved (e.g., a CirclePixelRegion converts to a CircleSkyRegion).

For WCS with distortions (e.g., SIP), the local Jacobian matrix of the WCS transformation is used to compute directional scale factors and angle. For WCS without distortions, a local pixel scale and angle are computed using offset-based methods.

to_spherical_sky(wcs=None, include_boundary_distortions=False, n_points=None)

Convert to an equivalent spherical SphericalSkyRegion instance.

Parameters:

wcsWCS instance, optional

The world coordinate system transformation to use to convert between sky and pixel coordinates. Required if transforming with boundary distortions (if include_boundary_distortions is True). Ignored if boundary distortions not included.

include_boundary_distortionsbool, optional

If True, accounts for boundary distortions in spherical to planar conversions, by discretizing the boundary and converting the boundary polygon. Default is False, which converts to an equivalent idealized shape.

n_pointsint, optional

The number of polygon vertices for boundary discretization. This keyword will have effect unless include_boundary_distortions=True. Default is 100.

Returns:

spherical_sky_regionSphericalSkyRegion

A spherical sky region, with an equivalent shape (if include_boundary_distortions is False), or a discretized polygon of the boundary (if include_boundary_distortions is True).