class matplotlib.patches.Arc(xy, width, height, angle=0.0, theta1=0.0, theta2=360.0, **kwargs)
[source]
Bases: matplotlib.patches.Ellipse
An elliptical arc. Because it performs various optimizations, it can not be filled.
The arc must be used in an Axes
instance---it can not be added directly to a Figure
---because it is optimized to only render the segments that are inside the axes bounding box with high resolution.
The following args are supported:
If theta1 and theta2 are not provided, the arc will form a complete ellipse.
Valid kwargs are:
Property | Description |
---|---|
agg_filter | a filter function, which takes a (m, n, 3) float array and a dpi value, and returns a (m, n, 3) array |
alpha | float or None |
animated | bool |
antialiased | unknown |
capstyle | {'butt', 'round', 'projecting'} |
clip_box | Bbox |
clip_on | bool |
clip_path | [(Path , Transform ) | Patch | None] |
color | color |
contains | callable |
edgecolor | color or None or 'auto' |
facecolor | color or None |
figure | Figure |
fill | bool |
gid | str |
hatch | {'/', '\', '|', '-', '+', 'x', 'o', 'O', '.', '*'} |
in_layout | bool |
joinstyle | {'miter', 'round', 'bevel'} |
label | object |
linestyle | {'-', '--', '-.', ':', '', (offset, on-off-seq), ...} |
linewidth | float or None for default |
path_effects | AbstractPathEffect |
picker | None or bool or float or callable |
rasterized | bool or None |
sketch_params | (scale: float, length: float, randomness: float) |
snap | bool or None |
transform | Transform |
url | str |
visible | bool |
zorder | float |
draw(renderer)
[source]
Ellipses are normally drawn using an approximation that uses eight cubic Bezier splines. The error of this approximation is 1.89818e-6, according to this unverified source:
Lancaster, Don. Approximating a Circle or an Ellipse Using Four Bezier Cubic Splines.
http://www.tinaja.com/glib/ellipse4.pdf
There is a use case where very large ellipses must be drawn with very high accuracy, and it is too expensive to render the entire ellipse with enough segments (either splines or line segments). Therefore, in the case where either radius of the ellipse is large enough that the error of the spline approximation will be visible (greater than one pixel offset from the ideal), a different technique is used.
In that case, only the visible parts of the ellipse are drawn, with each visible arc using a fixed number of spline segments (8). The algorithm proceeds as follows:
The points where the ellipse intersects the axes bounding box are located. (This is done be performing an inverse transformation on the axes bbox such that it is relative to the unit circle -- this makes the intersection calculation much easier than doing rotated ellipse intersection directly).
This uses the "line intersecting a circle" algorithm from:
Vince, John. Geometry for Computer Graphics: Formulae, Examples & Proofs. London: Springer-Verlag, 2005.
matplotlib.path.Path.arc()
. matplotlib.patches.Arc
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Licensed under the Matplotlib License Agreement.
https://matplotlib.org/3.0.0/api/_as_gen/matplotlib.patches.Arc.html