Reading ARC entity attributes

[zizlee]

When I use ezdxf to read a DXF file, I have noticed that there seem to be some issues with the attributes of the arc entities it reads.

In the DXF file, there are two arc entities with the following attributes:

Arc 1:

Start point = (-32.766, -21.449, 0.000)
End point = (-35.222, 5.762, 0.000)
Center point = (-128.720, -16.392, 0.000)
Radius = 96.087
Arc 2:

Start point = (-32.766, -21.449, -0.000)
End point = (-33.718, -33.593, -0.000)
Center point = (-251.728, -10.406, -0.000)
Radius = 219.240
Angle = 3.18374 degrees
Angle = 16.3467 degrees

When I read the entities,I received the following results, indicating an issue with the center of the second entity (arc):

Arc 1:

Start point = (-32.76640220009109, -21.448953455001394, 1.073e-12)
End point = (-35.221821844037564, 5.761628669883095, 1.073e-12)
Center = (-128.7202735966373, -16.39153089674467, 1.073e-12)
Radius = 96.08705926875737
Arc 2:

Start point = (-32.76640220009119, -21.448953455001377, -7.8756e-12)
End point = (-33.71764943317234, -33.592642530491965, -7.8756e-12)
Center = (251.728240057663, -10.40619587545267, 7.8756e-12)
Radius = 219.2401170701344

Show my code:

import ezdxf
print(ezdxf.version)

doc = ezdxf.readfile('arc_test.dxf')
msp = doc.modelspace()

for e in msp:
    print('Start point:', e.start_point)
    print('End point:', e.end_point)
    print('Center:', e.dxf.center)
    print('Radius:', e.dxf.radius)

[mozman]

The ARC entity is an OCS entiy. Search for the term OCS in the docs or in the forum.

[mozman]

I added FAQ #1266 for that.