src/reportlab/pdfgen/pdfgeom.py
 author robin Tue, 07 Mar 2017 10:00:34 +0000 changeset 4330 617ffa6bbdc8 parent 4252 fe660f227cac child 4370 823a8c33ce43 permissions -rwxr-xr-x
changes for release 3.4.0
```
#history http://www.reportlab.co.uk/cgi-bin/viewcvs.cgi/public/reportlab/trunk/reportlab/pdfgen/pdfgeom.py
__version__='3.3.0'
__doc__="""
This module includes any mathematical methods needed for PIDDLE.
It should have no dependencies beyond the Python library.

So far, just Robert Kern's bezierArc.
"""

from math import sin, cos, pi, ceil

def bezierArc(x1,y1, x2,y2, startAng=0, extent=90):
"""bezierArc(x1,y1, x2,y2, startAng=0, extent=90) --> List of Bezier
curve control points.

(x1, y1) and (x2, y2) are the corners of the enclosing rectangle.  The
coordinate system has coordinates that increase to the right and down.
Angles, measured in degress, start with 0 to the right (the positive X
axis) and increase counter-clockwise.  The arc extends from startAng
to startAng+extent.  I.e. startAng=0 and extent=180 yields an openside-down
semi-circle.

The resulting coordinates are of the form (x1,y1, x2,y2, x3,y3, x4,y4)
such that the curve goes from (x1, y1) to (x4, y4) with (x2, y2) and
(x3, y3) as their respective Bezier control points."""

x1,y1, x2,y2 = min(x1,x2), max(y1,y2), max(x1,x2), min(y1,y2)

if abs(extent) <= 90:
arcList = [startAng]
fragAngle = float(extent)
Nfrag = 1
else:
arcList = []
Nfrag = int(ceil(abs(extent)/90.))
fragAngle = float(extent) / Nfrag

x_cen = (x1+x2)/2.
y_cen = (y1+y2)/2.
rx = (x2-x1)/2.
ry = (y2-y1)/2.
halfAng = fragAngle * pi / 360.
kappa = abs(4. / 3. * (1. - cos(halfAng)) / sin(halfAng))

if fragAngle < 0:
sign = -1
else:
sign = 1

pointList = []

for i in range(Nfrag):
theta0 = (startAng + i*fragAngle) * pi / 180.
theta1 = (startAng + (i+1)*fragAngle) *pi / 180.
if fragAngle > 0:
pointList.append((x_cen + rx * cos(theta0),
y_cen - ry * sin(theta0),
x_cen + rx * (cos(theta0) - kappa * sin(theta0)),
y_cen - ry * (sin(theta0) + kappa * cos(theta0)),
x_cen + rx * (cos(theta1) + kappa * sin(theta1)),
y_cen - ry * (sin(theta1) - kappa * cos(theta1)),
x_cen + rx * cos(theta1),
y_cen - ry * sin(theta1)))
else:
pointList.append((x_cen + rx * cos(theta0),
y_cen - ry * sin(theta0),
x_cen + rx * (cos(theta0) + kappa * sin(theta0)),
y_cen - ry * (sin(theta0) - kappa * cos(theta0)),
x_cen + rx * (cos(theta1) - kappa * sin(theta1)),
y_cen - ry * (sin(theta1) + kappa * cos(theta1)),
x_cen + rx * cos(theta1),
y_cen - ry * sin(theta1)))

return pointList
```