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fixes wrong length of flat quadratic bezier #240

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fixes wrong length of flat quadratic bezier #240

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dc745b8
Merge pull request #1 from mathandy/master
derVedro Nov 12, 2017
613c369
Merge branch 'mathandy:master' into master
derVedro Nov 26, 2025
f170ccc
fixed wrong length of flat quadratic bezier
derVedro Nov 26, 2025
c70849b
test for flat quadratic bezier
derVedro Nov 26, 2025
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7 changes: 4 additions & 3 deletions svgpathtools/path.py
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Original file line number Diff line number Diff line change
Expand Up @@ -957,10 +957,11 @@ def length(self, t0=0, t1=1, error=None, min_depth=None):

dq1_mag = sqrt(c2 * t1 ** 2 + c1 * t1 + c0)
dq0_mag = sqrt(c2 * t0 ** 2 + c1 * t0 + c0)
logarand = (sqrt(c2) * (t1 + beta) + dq1_mag) / \
(sqrt(c2) * (t0 + beta) + dq0_mag)
rand_num = sqrt(c2) * (t1 + beta) + dq1_mag
rand_den = sqrt(c2) * (t0 + beta) + dq0_mag
logarand = log(rand_num / rand_den) if rand_den != 0 else 0
s = (t1 + beta) * dq1_mag - (t0 + beta) * dq0_mag + \
gamma * sqrt(c2) * log(logarand)
gamma * sqrt(c2) * logarand
s /= 2
if isnan(s):
tstar = abs(b) / (2 * abs(a))
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5 changes: 5 additions & 0 deletions test/test_path.py
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Original file line number Diff line number Diff line change
Expand Up @@ -500,6 +500,11 @@ def test_length(self):
for t0, t1, exp_s in tests:
self.assertAlmostEqual(linq2.length(t0=t0, t1=t1), exp_s, delta=TOL)

# flat quadratic bezier curve should be almost as long as a straight line
flat_quad_bez = QuadraticBezier(start=46 + 125j, control=45.8 + 124.6j, end=45.7 + 124.4j)
line = Line(start=46 + 125j, end=45.7 + 124.4j)
self.assertAlmostEqual(flat_quad_bez.length(), line.length(), delta=TOL)

def test_equality(self):
# This is to test the __eq__ and __ne__ methods, so we can't use
# assertEqual and assertNotEqual
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