How to calculate area of closed contour

[dizzysan84]

Hello,

I get an dxf file from metal forming simulation software with closed contour of billet made by LINES entities.

Could you please guide my how to calculate area of the contour?

I have check @catalinanesia thread but it doesn't work in my case as consider only LWPOLYLINE and POLYLINE.

Contour1.zip

[gswifort]

Check this solution.
It only checks if the beginning of a line matches the end of another line, it does not check, for example, if the end matches the end. It works for the attached file, I don't know about your other files.

import ezdxf
import ezdxf.entities
import numpy as np
import shapely


def get_vertices(ents):
    for ent in ents:
        if isinstance(ent, ezdxf.entities.Line):
            yield tuple(ent.dxf.start)[:2], tuple(ent.dxf.end)[:2]
        elif isinstance(ent, ezdxf.entities.LWPolyline):
            yield tuple(ent.vertices())


def iter_sorted(vertices, order):
    _order = dict(order)
    p1, p2 = _order.popitem()
    yield from vertices[p1][:-1]
    yield from vertices[p2][:-1]
    while _order:
        p2 = _order.pop(p2)
        yield from vertices[p2][:-1]


def main():
    doc = ezdxf.readfile(r"d:\Users\GSWI\Download\Contour1.dxf")
    msp = doc.modelspace()
    ents = msp.query("LINE LWPOLYLINE")

    vertices = tuple(get_vertices(ents))
    start = np.array([i[0] for i in vertices])
    end = np.array([i[-1] for i in vertices])
    se_match = np.all(np.isclose(start[:, None], end), axis=-1)
    assert np.all(np.sum(se_match, axis=-1) == 1)
    match_pos = np.argmax(se_match, axis=-1)
    order = np.hstack((match_pos[:, None], np.arange(match_pos.shape[0])[:, None]))

    polygon = shapely.Polygon(tuple(iter_sorted(vertices, order)))

    print(f"Area: {polygon.area}")


if __name__ == "__main__":
    main()

[gswifort]

You can also do it simpler :)

import ezdxf
import ezdxf.entities
import shapely


def get_lines(ents):
    for ent in ents:
        if isinstance(ent, ezdxf.entities.Line):
            yield tuple(ent.dxf.start)[:2], tuple(ent.dxf.end)[:2]
        elif isinstance(ent, ezdxf.entities.LWPolyline):
            yield tuple(ent.vertices())


def main():
    doc = ezdxf.readfile(r"...")
    msp = doc.modelspace()
    ents = msp.query("LINE LWPOLYLINE")

    ls = shapely.MultiLineString(tuple(get_lines(ents)))
    lm = shapely.line_merge(ls)
    polygon = shapely.Polygon(lm)

    print(f"Area: {polygon.area}")


if __name__ == "__main__":
    main()

[dizzysan84]

Wow, thank you a lot! It works perfectly!