# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""
This module defines polygon regions in both pixel and sky coordinates.
"""
import astropy.units as u
import numpy as np
from regions._geometry import polygonal_overlap_grid
from regions._geometry.pnpoly import points_in_polygon
from regions.core.attributes import (OneDPixCoord, OneDSkyCoord,
PositiveScalar, RegionMetaDescr,
RegionVisualDescr, ScalarAngle,
ScalarPixCoord)
from regions.core.bounding_box import RegionBoundingBox
from regions.core.core import PixelRegion, SkyRegion
from regions.core.mask import RegionMask
from regions.core.metadata import RegionMeta, RegionVisual
from regions.core.pixcoord import PixCoord
__all__ = ['PolygonPixelRegion', 'RegularPolygonPixelRegion',
'PolygonSkyRegion']
[docs]
class PolygonPixelRegion(PixelRegion):
"""
A polygon in pixel coordinates.
Parameters
----------
vertices : `~regions.PixCoord`
The vertices of the polygon.
meta : `~regions.RegionMeta` or `dict`, optional
A dictionary that stores the meta attributes of the region.
visual : `~regions.RegionVisual` or `dict`, optional
A dictionary that stores the visual meta attributes of the
region.
origin : `~regions.PixCoord`, optional
The origin for polynomial vertices. Using this keyword allows
``vertices`` to be specified relative to an origin pixel
coordinate.
Examples
--------
.. plot::
:include-source:
from regions import PixCoord, PolygonPixelRegion
import matplotlib.pyplot as plt
fig, ax = plt.subplots(1, 1)
x, y = [45, 45, 55, 60], [75, 70, 65, 75]
vertices = PixCoord(x=x, y=y)
reg = PolygonPixelRegion(vertices=vertices)
patch = reg.plot(ax=ax, facecolor='none', edgecolor='red', lw=2,
label='Polygon')
ax.legend(handles=(patch,), loc='upper center')
ax.set_xlim(30, 80)
ax.set_ylim(50, 80)
ax.set_aspect('equal')
"""
_params = ('vertices',)
_mpl_artist = 'Patch'
vertices = OneDPixCoord('The vertices of the polygon as a |PixCoord| '
'array.')
meta = RegionMetaDescr('The meta attributes as a |RegionMeta|')
visual = RegionVisualDescr('The visual attributes as a |RegionVisual|.')
def __init__(self, vertices, meta=None, visual=None,
origin=PixCoord(0, 0)):
self._vertices = vertices
self.meta = meta or RegionMeta()
self.visual = visual or RegionVisual()
self.origin = origin
self.vertices = vertices + origin
@property
def area(self):
# See https://stackoverflow.com/questions/24467972
# Use offsets to improve numerical precision
x_ = self.vertices.x - self.vertices.x.mean()
y_ = self.vertices.y - self.vertices.y.mean()
# Shoelace formula, for our case where the start vertex
# isn't duplicated at the end, written to avoid an array copy
area_main = np.dot(x_[:-1], y_[1:]) - np.dot(y_[:-1], x_[1:])
area_last = x_[-1] * y_[0] - y_[-1] * x_[0]
return 0.5 * np.abs(area_main + area_last)
[docs]
def contains(self, pixcoord):
pixcoord = PixCoord._validate(pixcoord, 'pixcoord')
x = np.atleast_1d(np.asarray(pixcoord.x, dtype=float))
y = np.atleast_1d(np.asarray(pixcoord.y, dtype=float))
vx = np.asarray(self.vertices.x, dtype=float)
vy = np.asarray(self.vertices.y, dtype=float)
shape = x.shape
mask = points_in_polygon(x.flatten(), y.flatten(), vx, vy).astype(bool)
in_poly = mask.reshape(shape)
if self.meta.get('include', True):
return in_poly
else:
return np.logical_not(in_poly)
[docs]
def to_sky(self, wcs):
vertices_sky = wcs.pixel_to_world(self.vertices.x, self.vertices.y)
return PolygonSkyRegion(vertices=vertices_sky, meta=self.meta.copy(),
visual=self.visual.copy())
@property
def bounding_box(self):
xmin = self.vertices.x.min()
xmax = self.vertices.x.max()
ymin = self.vertices.y.min()
ymax = self.vertices.y.max()
return RegionBoundingBox.from_float(xmin, xmax, ymin, ymax)
[docs]
def to_mask(self, mode='center', subpixels=5):
self._validate_mode(mode, subpixels)
if mode == 'center':
mode = 'subpixels'
subpixels = 1
if mode == 'subpixels':
use_exact = 0
else:
use_exact = 1
# Find bounding box and mask size
bbox = self.bounding_box
ny, nx = bbox.shape
# Find position of pixel edges and recenter so that circle is at
# origin
xmin = float(bbox.ixmin) - 0.5
xmax = float(bbox.ixmax) - 0.5
ymin = float(bbox.iymin) - 0.5
ymax = float(bbox.iymax) - 0.5
vx = np.asarray(self.vertices.x, dtype=float)
vy = np.asarray(self.vertices.y, dtype=float)
fraction = polygonal_overlap_grid(xmin, xmax, ymin, ymax, nx, ny,
vx, vy, use_exact, subpixels)
return RegionMask(fraction, bbox=bbox)
[docs]
def as_artist(self, origin=(0, 0), **kwargs):
"""
Return a matplotlib patch object for this region
(`matplotlib.patches.Polygon`).
Parameters
----------
origin : array_like, optional
The ``(x, y)`` pixel position of the origin of the displayed
image.
**kwargs : dict
Any keyword arguments accepted by
`~matplotlib.patches.Polygon`. These keywords will override
any visual meta attributes of this region.
Returns
-------
artist : `~matplotlib.patches.Polygon`
A matplotlib polygon patch.
"""
from matplotlib.patches import Polygon
xy = np.vstack([self.vertices.x - origin[0],
self.vertices.y - origin[1]]).transpose()
mpl_kwargs = self.visual.define_mpl_kwargs(self._mpl_artist)
mpl_kwargs.update(kwargs)
return Polygon(xy=xy, **mpl_kwargs)
[docs]
def rotate(self, center, angle):
"""
Rotate the region.
Positive ``angle`` corresponds to counter-clockwise rotation.
Parameters
----------
center : `~regions.PixCoord`
The rotation center point.
angle : `~astropy.coordinates.Angle`
The rotation angle.
Returns
-------
region : `PolygonPixelRegion`
The rotated region (which is an independent copy).
"""
vertices = self.vertices.rotate(center, angle)
return self.copy(vertices=vertices)
[docs]
class RegularPolygonPixelRegion(PolygonPixelRegion):
"""
A regular polygon in pixel coordinates.
.. note::
This class will be serialized as a generic polygon
region, thus when read back in it will produce a
`~regions.PolygonPixelRegion` object instead of a
`~regions.RegularPolygonPixelRegion` object.
Parameters
----------
center : `~regions.PixCoord`
The position of the center of the polygon.
nvertices : `~regions.PixCoord`
The number of polygon vertices (or sides).
radius : float
The distance from the center to any vertex. This is also known
as the circumradius.
angle : `~astropy.units.Quantity`, optional
The rotation angle of the polygon, measured anti-clockwise. If
set to zero (the default), the polygon will point "up" following
the `matplotlib.patches.RegularPolygon` convention.
meta : `~regions.RegionMeta` or `dict`, optional
A dictionary that stores the meta attributes of the region.
visual : `~regions.RegionVisual` or `dict`, optional
A dictionary that stores the visual meta attributes of the
region.
Attributes
----------
side_length : float
The side length.
inradius : float
The radius of the largest circle contained entirely within the
polygon. This value is identical to the length of a line segment
from the polygon center to the midpoint of one of its sides
(known as as the apothem).
perimeter : float
The polygon perimeter.
interior_angle : float
The polygon interior angle, which is the angle at each vertex on
the inside of the polygon.
exterior_angle : float
The polygon exterior angle, which is an angle at each vertex on
the outside of the polygon.
Examples
--------
.. plot::
:include-source:
import astropy.units as u
import matplotlib.pyplot as plt
from regions import PixCoord, RegularPolygonPixelRegion
fig, ax = plt.subplots(1, 1)
center = PixCoord(x=50, y=50)
reg1 = RegularPolygonPixelRegion(center, 6, 15)
reg1.plot(edgecolor='red', lw=2)
center = PixCoord(x=25, y=25)
reg2 = RegularPolygonPixelRegion(center, 3, 15)
reg2.plot(edgecolor='green', lw=2)
center = PixCoord(x=25, y=75)
reg3 = RegularPolygonPixelRegion(center, 3, 15, angle=25*u.deg)
reg3.plot(edgecolor='orange', lw=2)
center = PixCoord(x=75, y=75)
reg4 = RegularPolygonPixelRegion(center, 8, 15)
reg4.plot(edgecolor='blue', lw=2)
center = PixCoord(x=75, y=25)
reg5 = RegularPolygonPixelRegion(center, 5, 15)
reg5.plot(edgecolor='magenta', lw=2)
ax.set_xlim(0, 100)
ax.set_ylim(0, 100)
ax.set_aspect('equal')
"""
_params = ('center', 'nvertices', 'radius', 'angle')
center = ScalarPixCoord('The center pixel position as a |PixCoord|.')
nvertices = PositiveScalar('The number of polygon vertices.')
radius = PositiveScalar('The distance from the center to any vertex in '
'pixels as a float.')
angle = ScalarAngle('The rotation angle measured anti-clockwise as a '
'|Quantity| angle.')
meta = RegionMetaDescr('The meta attributes as a |RegionMeta|')
visual = RegionVisualDescr('The visual attributes as a |RegionVisual|.')
def __init__(self, center, nvertices, radius, angle=0. * u.deg,
meta=None, visual=None):
if nvertices < 3:
raise ValueError('nvertices must be >= 3')
self.center = center
self.nvertices = nvertices
self.radius = radius
self.angle = angle
super().__init__(self._calc_vertices(), meta=meta, visual=visual)
self.side_length = 2. * self.radius * np.sin(np.pi / self.nvertices)
self.inradius = self.radius * np.cos(np.pi / self.nvertices)
self.perimeter = self.side_length * self.nvertices
self.interior_angle = ((self.nvertices - 2) / self.nvertices
* 180) << u.deg
self.exterior_angle = 360. / self.nvertices << u.deg
def _calc_vertices(self):
# uses the matplotlib convention that the polygon always points "up"
theta = ((2. * np.pi / self.nvertices * np.arange(self.nvertices)
+ (np.pi / 2)) << u.radian) + self.angle
xvert = self.radius * np.cos(theta)
yvert = self.radius * np.sin(theta)
return self.center + PixCoord(xvert, yvert)
[docs]
def rotate(self, center, angle):
"""
Rotate the region.
Positive ``angle`` corresponds to counter-clockwise rotation.
Parameters
----------
center : `~regions.PixCoord`
The rotation center point.
angle : `~astropy.coordinates.Angle`
The rotation angle.
Returns
-------
region : `PolygonPixelRegion`
The rotated region (which is an independent copy).
"""
center = self.center.rotate(center, angle)
angle = self.angle + angle
return self.copy(center=center, angle=angle)
[docs]
def to_polygon(self):
"""
Return a `PolygonPixelRegion` of this region.
"""
return PolygonPixelRegion(self.vertices, origin=PixCoord(0, 0),
meta=self.meta.copy(),
visual=self.visual.copy())
[docs]
class PolygonSkyRegion(SkyRegion):
"""
A polygon defined using vertices in sky coordinates.
Parameters
----------
vertices : `~astropy.coordinates.SkyCoord`
The vertices of the polygon.
meta : `~regions.RegionMeta` or `dict`, optional
A dictionary that stores the meta attributes of the region.
visual : `~regions.RegionVisual` or `dict`, optional
A dictionary that stores the visual meta attributes of the
region.
"""
_params = ('vertices',)
vertices = OneDSkyCoord('The vertices of the polygon as a |SkyCoord| '
'array.')
meta = RegionMetaDescr('The meta attributes as a |RegionMeta|')
visual = RegionVisualDescr('The visual attributes as a |RegionVisual|.')
def __init__(self, vertices, meta=None, visual=None):
self.vertices = vertices
self.meta = meta or RegionMeta()
self.visual = visual or RegionVisual()
[docs]
def to_pixel(self, wcs):
x, y = wcs.world_to_pixel(self.vertices)
vertices_pix = PixCoord(x, y)
return PolygonPixelRegion(vertices_pix, meta=self.meta.copy(),
visual=self.visual.copy())