How to convert LINE WITH ARC TO POLYLINE ?

[LaimisMasaitis]

hi i want to convert rectangle with fillets on the corners(from lines and arcs) to polyline.
Well task is not very simple. Because at first need to find lines, arcs, points, calculate arcs bulges, insert points and bulge data to draw polyline, delete old lines, arcs, save everything in the new file . But I cant to find 100% working example. Help me please.
this code draws nonsenses:

import ezdxf
import math

def arc_endpoints(arc):
    """Calculate start and end points of an ARC entity."""
    cx, cy = arc.dxf.center.x, arc.dxf.center.y  # Arc center
    radius = arc.dxf.radius

    # Convert angles to radians
    start_angle = math.radians(arc.dxf.start_angle)
    end_angle = math.radians(arc.dxf.end_angle)

    # Compute start and end points
    start_point = (cx + radius * math.cos(start_angle), cy + radius * math.sin(start_angle))
    end_point = (cx + radius * math.cos(end_angle), cy + radius * math.sin(end_angle))

    return start_point, end_point

def calculate_bulge(arc):
    """Calculate the bulge factor for an ARC entity."""
    start_angle = math.radians(arc.dxf.start_angle)
    end_angle = math.radians(arc.dxf.end_angle)

    # Arc sweep angle (always counterclockwise in DXF)
    sweep_angle = end_angle - start_angle
    if sweep_angle < 0:
        sweep_angle += 2 * math.pi  # Normalize to 0-360 degrees

    # Compute bulge
    bulge = math.tan(sweep_angle / 4)

    # Check extrusion direction (Z-axis)
    if arc.dxf.hasattr("extrusion") and arc.dxf.extrusion.z < 0:
        bulge = -bulge  # Negate bulge for clockwise arcs

    return bulge


def convert_lines_arcs_to_polyline(msp):
    """Finds all LINE and ARC entities and converts them to a single LWPOLYLINE."""
    entities = list(msp.query("LINE ARC"))  # Get all lines and arcs
    print("entities", entities, )
    if not entities:
        print("No lines or arcs found!")
        return

    points = []

    for entity in entities:
        if entity in doc.modelspace().query('LINE'):
            points.append((entity.dxf.start.x, entity.dxf.start.y, 0))  # No bulge for lines

        elif entity in doc.modelspace().query('ARC'):
            start_point, _ = arc_endpoints(entity)  # Get start point of arc
            bulge = calculate_bulge(entity)  # Compute bulge value

            points.append((start_point[0], start_point[1], bulge))

    # Add last point (end of the last entity)
    last_entity = entities[-1]
    if last_entity in doc.modelspace().query('LINE'):
        points.append((last_entity.dxf.end.x, last_entity.dxf.end.y, 0))
    
    elif last_entity in doc.modelspace().query('ARC'):
        _, end_point = arc_endpoints(last_entity)  # Get end point of last arc
        points.append((end_point[0], end_point[1], 0))  # Last point has no bulge

    # Create the LWPOLYLINE with bulge values
    polyline = msp.add_lwpolyline(points, format="xb", close=False)  # "xb" = X-coord + bulge
    print("Polyline created:", polyline")

    # Optional: Delete old lines & arcs
    for entity in entities:
        msp.delete_entity(entity)

    print("Conversion completed!")

# Load DXF and apply conversion
doc = ezdxf.readfile("C:\\Pjovimas\pjovimas1.dxf")
msp = doc.modelspace()
convert_lines_arcs_to_polyline(msp)
doc.saveas("C:\\Pjovimas\pjovimas2.dxf")

[mozman]

Look at the new ezdxf.edgeminer and ezdxf.edgesmith modules. Only available in the current beta releases of v1.4.

Tutorial: https://ezdxf.mozman.at/docs/tutorials/edges.html

import ezdxf
from ezdxf import edgeminer as em
from ezdxf import edgesmith as es


def main():
    doc = ezdxf.readfile("rounded_rectangle.dxf")   # see attached zip archive
    msp = doc.modelspace()

    # create edges and deposit
    entities = msp.query("LINE ARC")
    edges = list(es.edges_from_entities_2d(entities))
    deposit = em.Deposit(edges)

    # find first closed loop
    loop = em.find_loop(deposit)

    if len(loop):
        # build LWPOLYLINE
        polyline = es.lwpolyline_from_chain(loop, dxfattribs={"color": 1})

        # export new DXF file
        doc_out = ezdxf.new()
        msp_out = doc_out.modelspace()
        msp_out.add_entity(polyline)
        doc_out.saveas("lwpolyline.dxf")
    else:
        print("polyline not found")

if __name__ == "__main__":
    main()

rounded_rectangle.zip

[LaimisMasaitis]

tested and my default ezdxf version only 1.1.4. How to upgrade in pycharm because i have error mentioned above?

[LaimisMasaitis]

Hi, instaled latest python and pycharm and everything works ok. Thank you mozman.

[LaimisMasaitis]

Hi i have noticed that code converts to polyline only one rectangle in the modelspace then others are ignored. How to convert multiple rectangles in model space? Is it possible?

[mozman]

There is a link to a tutorial.

[LaimisMasaitis]

Aha i see tutorial and i have problem with code. This my code compile but it coverts one rectangle anyway. I think i have loop problem with smith :) i need help with code!

doc = ezdxf.readfile(r"C:\Pjovimas\pjovimas2.dxf")
msp = doc.modelspace()
lines = msp.query("LINE ARC")

create edges and search index

edges = list(edgesmith.edges_from_entities_2d(lines))
deposit = edgeminer.Deposit(edges)

find chains

chains = edgeminer.find_all_simple_chains(deposit)

create a new output document

for chain in chains:
polyline = edgesmith.lwpolyline_from_chain(
chain
)
msp.add_entity(polyline)

loops = edgeminer.find_all_loops(deposit)

create a new output document

out = ezdxf.new()
msp = out.modelspace()

for loop in loops:
#layer = f"LOOP_{color}"
polyline = edgesmith.lwpolyline_from_chain(
loop,
)
msp.add_entity(polyline)

out.saveas(r"C:\Pjovimas\pjovimas4.dxf")