How to control the line width of the drawing add-on output

[qing0]

Hello,@mozman

If the dxf file contains very few entities, the dxf converted to png will have very shallow lines in the png. It seems to stretch the already small figure in equal proportion, but the lines do not thicken in equal proportion.
Below are the dxf files I used for testing and the png images I generated.

test.zip

Is there any way to generate png images with different thickness lines according to the number of different entities or the overall size of the dxf file？

[mozman]

The line width is always an absolute width regardless of the paper size e.g. 0.25mm is always 0.25mm for any paper size.

Matplotlib's auto-scaling feature makes it difficult to control the output paper size. This how-to section shows how to set a specific paper size in inches (matplotlib supports this feature only in inches, 1 in = 25.4 mm).

fig.set_size_inches(8, 11)

Alternatively, you can set the minimum line width in the configuration settings:

import matplotlib.pyplot as plt

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

doc = ezdxf.readfile("your.dxf")
msp = doc.modelspace()

# setup drawing add-on configuration
config = Configuration.defaults()
config = config.with_changes(
    min_lineweight=11.8,  # in 1/300 inch: 1 mm = 1mm / 25.4 * 300
)

fig: plt.Figure = plt.figure(dpi=300)
ax: plt.Axes = fig.add_axes([0, 0, 1, 1])
ctx = RenderContext(doc)
out = MatplotlibBackend(ax)

Frontend(ctx, out, config=config).draw_layout(msp, finalize=True)

There exist also a lineweight_scaling factor in the configuration settings, e.g. scale all lineweights by factor 3:

config = config.with_changes(
    min_lineweight=11.8,  # in 1/300 inch: 1 mm = 1mm / 25.4 * 300,
    lineweight_scaling=3.0,
)

And there are additional how-to's for controlling pixel density per drawing unit or output scale.

EDIT: With pixel-based output formats (PNG, JPEG) it is very important to set a suitable DPI value (dots per inch)!

[qing0]

Thanks for your reply!
I know how to deal with it.

[mozman]

The following table shows the line width in pixels for all valid DXF lineweights for a resolution of 72, 100, 200 and 300 dpi:

lineweights.ods
lineweights.pdf

[qing0]

Very helpful, thank you!

[Kaviraj-vg]

depending on the size of the file, the lineweight value differs for shapes in pdf file

we can decativate this by giving lineweight_scaling=0.0,

but i need to export a pdf file(having different lineweights for different shapes) that don't change lineweight value based on the scaling

anyone with solution for this ?
this is the code i used to export my pdf file

def pdf_creation(self):
        
        ax: plt.Axes = self.fig.add_axes([0, 0, 1, 1])
        ctx = RenderContext(self.doc)

        # Get the modelspace properties
        msp_properties = LayoutProperties.from_layout(self.msp)

        # Set light gray background color and black foreground color
        msp_properties.set_colors("#FFFFFF", "#000000")
        # msp_properties.lineweight_scaling = 1.0
        # for entity in self.msp:
        #     entity.dxf.lineweight = -3
        config = Configuration.defaults()
        config = config.with_changes(
            min_lineweight=0.05,  # in 1/300 inch: 1 mm = 1mm / 25.4 * 300
            lineweight_scaling=0.5
        )
        out = MatplotlibBackend(ax)

        # Override the layout properties and render the modelspace
        Frontend(ctx, out,config=config).draw_layout(self.msp, finalize=True, layout_properties=msp_properties)