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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 Parameters
---------- ----------
start : complex 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 radius : complex
rx + 1j*ry, where rx and ry are the radii of the ellipse (also 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 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 This is the CCW angle (in degrees) from the positive x-axis of the
current coordinate system to the x-axis of the ellipse. current coordinate system to the x-axis of the ellipse.
large_arc : bool large_arc : bool
This is the large_arc flag. Given two points on an ellipse, Given two points on an ellipse, there are two elliptical arcs
there are two elliptical arcs connecting those points, the first connecting those points, the first going the short way around the
going the short way around the ellipse, and the second going the ellipse, and the second going the long way around the ellipse. If
long way around the ellipse. If large_arc is 0, the shorter `large_arc == False`, the shorter elliptical arc will be used. If
elliptical large_arc will be used. If large_arc is 1, then longer `large_arc == True`, then longer elliptical will be used.
elliptical will be used. In other words, `large_arc` should be 0 for arcs spanning less than
In other words, it should be 0 for arcs spanning less than or or equal to 180 degrees and 1 for arcs spanning greater than 180
equal to 180 degrees and 1 for arcs spanning greater than 180
degrees. degrees.
sweep : bool sweep : bool
This is the sweep flag. For any acceptable parameters start, end, For any acceptable parameters `start`, `end`, `rotation`, and
rotation, and radius, there are two ellipses with the given major `radius`, there are two ellipses with the given major and minor
and minor axes (radii) which connect start and end. One which axes (radii) which connect `start` and `end`. One which connects
connects them in a CCW fashion and one which connected them in a them in a CCW fashion and one which connected them in a CW
CW fashion. If sweep is 1, the CCW ellipse will be used. If fashion. If `sweep == True`, the CCW ellipse will be used. If
sweep is 0, the CW ellipse will be used. See note on curve `sweep == False`, the CW ellipse will be used. See note on curve
orientation below. orientation below.
end : complex 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 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 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 Derived Parameters/Attributes
----------------------------- -----------------------------
@ -1182,6 +1183,8 @@ class Arc(object):
in some sense when viewing SVGs (as the y coordinate starts at the top in some sense when viewing SVGs (as the y coordinate starts at the top
of the image and increases towards the bottom). of the image and increases towards the bottom).
""" """
assert start != end
assert radius.real > 0 and radius.imag > 0
self.start = start self.start = start
self.radius = abs(radius.real) + 1j*abs(radius.imag) self.radius = abs(radius.real) + 1j*abs(radius.imag)
@ -1218,10 +1221,6 @@ class Arc(object):
return not self == other return not self == other
def _parameterize(self): 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 # See http://www.w3.org/TR/SVG/implnote.html#ArcImplementationNotes
# my notation roughly follows theirs # my notation roughly follows theirs
rx = self.radius.real rx = self.radius.real