How do I get a more accurate linetype rendering for the drawing add-on

[radheygupta]

I am trying to convert a DXF file to a black&white png file. During the conversion some lines(dotted/dashed) are drawn differently. Every line type have its special meaning so it should be drawn exactly same.
For example in the attached screenshot DXF have dashed horizontal and vertical lines within the circle. While png version have different types of lines within the circle.

I have also attached the actual files for the reference.
line_type_issue.zip

[mozman]

The default rendering mode for line types in the drawing add-on is APPROIXIMATE, which uses the line type rendering provided by the backend. Matplotlib and PyQt render line types in such a way that the same line pattern is always displayed regardless of the view scaling or zoom level. The ACCURATE line policy is implemented for both backends, which shows a more precise rendering. The modified code uses the new configuration system for the drawing add-on and requires ezdxf v0.17 run:

from pathlib import Path

import matplotlib.figure as figure
import ezdxf
from ezdxf.addons.drawing import RenderContext, Frontend
from ezdxf.addons.drawing.matplotlib import MatplotlibBackend
from ezdxf.addons.drawing.config import Configuration, LinePolicy

# set your working directory:
DIR = Path("~/Desktop/Now/ezdxf/561").expanduser()

def convert_dxf2img(name: Path):

    doc = ezdxf.readfile(name)
    msp = doc.modelspace()

    # new configuration system for the drawing add-on in ezdxf v0.17:
    config = Configuration.defaults()
    config = config.with_changes(line_policy=LinePolicy.ACCURATE)

    fig = figure.Figure()
    ax = fig.add_axes([0, 0, 1, 1])
    ctx = RenderContext(doc)
    ctx.set_current_layout(msp)
    ctx.current_layout_properties.set_colors(bg="#ffffff", fg="#000000")
    out = MatplotlibBackend(ax)
    frontend = Frontend(ctx, out, config=config)
    frontend.draw_layout(msp, finalize=True)
    fig.savefig(name.with_suffix(".png"), dpi=300)


if __name__ == "__main__":
    convert_dxf2img(DIR / "MBV1G-PB0000047471-2012-06-01-DE-3.dxf")