Bases: matplotlib.patches.Ellipse
An elliptical arc, i.e. a segment of an ellipse.
Due to internal optimizations, there are certain restrictions on using Arc:
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 center of the ellipse.
The length of the horizontal axis.
The length of the vertical axis.
Rotation of the ellipse in degrees (counterclockwise).
Starting and ending angles of the arc in degrees. These values are relative to angle, e.g. if angle = 45 and theta1 = 90 the absolute starting angle is 135. Default theta1 = 0, theta2 = 360, i.e. a complete ellipse. The arc is drawn in the counterclockwise direction. Angles greater than or equal to 360, or smaller than 0, are represented by an equivalent angle in the range [0, 360), by taking the input value mod 360.
Patch properties
Most Patch properties are supported as keyword arguments, with the exception of fill and facecolor because filling is not supported.
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 or aa unknown capstyle {'butt', 'round', 'projecting'} clip_box Bbox clip_on bool clip_path Patch or (Path, Transform) or None color color contains unknown edgecolor or ec color or None or 'auto' facecolor or fc color or None figure Figure fill bool gid str hatch {'/', '\', '|', '-', '+', 'x', 'o', 'O', '.', '*'} in_layout bool joinstyle {'miter', 'round', 'bevel'} label object linestyle or ls {'-', '--', '-.', ':', '', (offset, on-off-seq), ...} linewidth or lw float or None path_effects AbstractPathEffect picker None or bool 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
__init__(self, xy, width, height, angle=0.0, theta1=0.0, theta2=360.0, **kwargs)[source]¶
The center of the ellipse.
The length of the horizontal axis.
The length of the vertical axis.
Rotation of the ellipse in degrees (counterclockwise).
Starting and ending angles of the arc in degrees. These values are relative to angle, e.g. if angle = 45 and theta1 = 90 the absolute starting angle is 135. Default theta1 = 0, theta2 = 360, i.e. a complete ellipse. The arc is drawn in the counterclockwise direction. Angles greater than or equal to 360, or smaller than 0, are represented by an equivalent angle in the range [0, 360), by taking the input value mod 360.
Patch properties
Most Patch properties are supported as keyword arguments, with the exception of fill and facecolor because filling is not supported.
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 or aa unknown capstyle {'butt', 'round', 'projecting'} clip_box Bbox clip_on bool clip_path Patch or (Path, Transform) or None color color contains unknown edgecolor or ec color or None or 'auto' facecolor or fc color or None figure Figure fill bool gid str hatch {'/', '\', '|', '-', '+', 'x', 'o', 'O', '.', '*'} in_layout bool joinstyle {'miter', 'round', 'bevel'} label object linestyle or ls {'-', '--', '-.', ':', '', (offset, on-off-seq), ...} linewidth or lw float or None path_effects AbstractPathEffect picker None or bool 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
__module__ = 'matplotlib.patches'¶
__str__(self)[source]¶
Return str(self).
draw(self, renderer)[source]¶
Draw the arc to the given renderer.
Notes
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:
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.
The angles of each of the intersection points are calculated.
Proceeding counterclockwise starting in the positive x-direction, each of the visible arc-segments between the pairs of vertices are drawn using the Bezier arc approximation technique implemented in Path.arc.
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