PolygonPixelRegion

class regions.PolygonPixelRegion(vertices, meta=None, visual=None, origin=None)

Bases: PixelRegion

A polygon in pixel coordinates.

Parameters:

verticesPixCoord

The vertices of the polygon.

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.

originPixCoord, optional

The origin for polynomial vertices. Using this keyword allows vertices to be specified relative to an origin pixel coordinate.

Examples

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')

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

Attributes Summary

area	The exact analytical area of the region shape.
bounding_box	The minimal bounding box (in integer pixel coordinates) that contains the region.
meta	The meta attributes as a RegionMeta
vertices	The vertices of the polygon as a PixCoord array.
visual	The visual attributes as a RegionVisual.

Methods Summary

as_artist([origin])	Return a matplotlib patch object for this region (matplotlib.patches.Polygon).
contains(pixcoord)	Check whether a position or positions fall inside the region.
rotate(center, angle)	Rotate the region.
to_mask([mode, subpixels])	Return a mask for the region.
to_sky(wcs)	Return a region defined in sky coordinates.

Attributes Documentation

area

bounding_box

meta

The meta attributes as a RegionMeta

vertices

The vertices of the polygon as a PixCoord array.

visual

The visual attributes as a RegionVisual.

Methods Documentation

as_artist(origin=(0, 0), **kwargs)

Return a matplotlib patch object for this region (matplotlib.patches.Polygon).

Parameters:

originarray_like, optional

The (x, y) pixel position of the origin of the displayed image.

**kwargsdict

Any keyword arguments accepted by Polygon. These keywords will override any visual meta attributes of this region.

Returns:

artistPolygon

A matplotlib polygon patch.

contains(pixcoord)

Check whether a position or positions fall inside the region.

Parameters:

pixcoordPixCoord

The position or positions to check.

rotate(center, angle)

Rotate the region.

Positive angle corresponds to counter-clockwise rotation.

Parameters:

centerPixCoord

The rotation center point.

angleAngle

The rotation angle.

Returns:

regionPolygonPixelRegion

The rotated region (which is an independent copy).

to_mask(mode='center', subpixels=5)

Return a mask for the region.

Parameters:

mode{‘center’, ‘exact’, ‘subpixels’}, optional

The method used to determine the overlap of the region on the pixel grid. Not all options are available for all region types. Note that the more precise methods are generally slower. The following methods are available:

• 'center': A pixel is considered to be entirely in or out of the region depending on whether its center is in or out of the region. The returned mask will contain values only of 0 (out) and 1 (in).

• 'exact' (default): The exact fractional overlap of the region and each pixel is calculated. The returned mask will contain values between 0 and 1.

• 'subpixel': A pixel is divided into subpixels (see the subpixels keyword), each of which are considered to be entirely in or out of the region depending on whether its center is in or out of the region. If subpixels=1, this method is equivalent to 'center'. The returned mask will contain values between 0 and 1.

subpixelsint, optional

For the 'subpixel' mode, resample pixels by this factor in each dimension. That is, each pixel is divided into subpixels ** 2 subpixels.

Returns:

maskRegionMask

A mask for the region.

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.