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improved Arc docstring and added positive radii assertion to Arc

pull/10/head
Andy 2017-02-20 20:11:54 -08:00
parent c219d1e671
commit a81af16d89
1 changed files with 21 additions and 22 deletions
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43
svgpathtools/path.py
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@ -1115,7 +1115,8 @@ class Arc(object):
Parameters
----------
start : complex
The start point of the large_arc.
The start point of the curve. Note: `start` and `end` cannot be the
same. To make a full ellipse or circle, use two `Arc` objects.
radius : complex
rx + 1j*ry, where rx and ry are the radii of the ellipse (also
known as its semi-major and semi-minor axes, or vice-versa or if
@ -1130,29 +1131,29 @@ class Arc(object):
This is the CCW angle (in degrees) from the positive x-axis of the
current coordinate system to the x-axis of the ellipse.
large_arc : bool
This is the large_arc flag. Given two points on an ellipse,
there are two elliptical arcs connecting those points, the first
going the short way around the ellipse, and the second going the
long way around the ellipse. If large_arc is 0, the shorter
elliptical large_arc will be used. If large_arc is 1, then longer
elliptical will be used.
In other words, it should be 0 for arcs spanning less than or
equal to 180 degrees and 1 for arcs spanning greater than 180
Given two points on an ellipse, there are two elliptical arcs
connecting those points, the first going the short way around the
ellipse, and the second going the long way around the ellipse. If
`large_arc == False`, the shorter elliptical arc will be used. If
`large_arc == True`, then longer elliptical will be used.
In other words, `large_arc` should be 0 for arcs spanning less than
or equal to 180 degrees and 1 for arcs spanning greater than 180
degrees.
sweep : bool
This is the sweep flag. For any acceptable parameters start, end,
rotation, and radius, there are two ellipses with the given major
and minor axes (radii) which connect start and end. One which
connects them in a CCW fashion and one which connected them in a
CW fashion. If sweep is 1, the CCW ellipse will be used. If
sweep is 0, the CW ellipse will be used. See note on curve
For any acceptable parameters `start`, `end`, `rotation`, and
`radius`, there are two ellipses with the given major and minor
axes (radii) which connect `start` and `end`. One which connects
them in a CCW fashion and one which connected them in a CW
fashion. If `sweep == True`, the CCW ellipse will be used. If
`sweep == False`, the CW ellipse will be used. See note on curve
orientation below.
end : complex
The end point of the large_arc (must be distinct from start).
The end point of the curve. Note: `start` and `end` cannot be the
same. To make a full ellipse or circle, use two `Arc` objects.
autoscale_radius : bool
If autoscale_radius == True, then will also scale self.radius
If `autoscale_radius == True`, then will also scale `self.radius`
in the case that no ellipse exists with the input parameters
(see in-line comments for further explanation).
(see inline comments for further explanation).
Derived Parameters/Attributes
-----------------------------
@ -1182,6 +1183,8 @@ class Arc(object):
in some sense when viewing SVGs (as the y coordinate starts at the top
of the image and increases towards the bottom).
"""
assert start != end
assert radius.real > 0 and radius.imag > 0
self.start = start
self.radius = abs(radius.real) + 1j*abs(radius.imag)
@ -1218,10 +1221,6 @@ class Arc(object):
return not self == other
def _parameterize(self):
# start cannot be the same as end as the ellipse would
# not be well defined
assert self.start != self.end
# See http://www.w3.org/TR/SVG/implnote.html#ArcImplementationNotes
# my notation roughly follows theirs
rx = self.radius.real