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import math
from affine import Affine
def test_rotation_angle():
"""A positive angle rotates a vector counter clockwise
(1.0, 0.0):
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0---------*
Affine.rotation(45.0) * (1.0, 0.0) == (0.707..., 0.707...)
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0----------
"""
x, y = Affine.rotation(45.0) * (1.0, 0.0)
assert round(x, 14) == round(math.sqrt(2.0) / 2.0, 14)
assert round(y, 14) == round(math.sqrt(2.0) / 2.0, 14)
def test_rotation_matrix():
"""A rotation matrix has expected elements
| cos(a) -sin(a) |
| sin(a) cos(a) |
"""
rot = Affine.rotation(90.0)
assert round(rot.a, 15) == round(math.cos(math.pi/2.0), 15)
assert round(rot.b, 15) == round(-math.sin(math.pi/2.0), 15)
assert rot.c == 0.0
assert round(rot.d, 15) == round(math.sin(math.pi/2.0), 15)
assert round(rot.e, 15) == round(math.cos(math.pi/2.0), 15)
assert rot.f == 0.0
def test_rotation_matrix_pivot():
"""A rotation matrix with pivot has expected elements"""
rot = Affine.rotation(90.0, pivot=(1.0, 1.0))
exp = (Affine.translation(1.0, 1.0)
* Affine.rotation(90.0)
* Affine.translation(-1.0, -1.0))
for r, e in zip(rot, exp):
assert round(r, 15) == round(e, 15)
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