Tutorial for Linetypes

Simple line type example:

../_images/ltype_simple.jpg

You can define your own linetypes. A linetype definition has a name, a description and line pattern elements:

elements = [total_pattern_length, elem1, elem2, ...]
total_pattern_length

Sum of all linetype elements (absolute values)

elem

if elem > 0 it is a line, if elem < 0 it is gap, if elem == 0.0 it is a dot

Create a new linetype definition:

import ezdxf
from ezdxf.tools.standards import linetypes  # some predefined linetypes

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

my_line_types = [
    (
        "DOTTED",
        "Dotted .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .",
        [0.2, 0.0, -0.2],
    ),
    (
        "DOTTEDX2",
        "Dotted (2x) .    .    .    .    .    .    .    . ",
        [0.4, 0.0, -0.4],
    ),
    (
        "DOTTED2",
        "Dotted (.5) . . . . . . . . . . . . . . . . . . . ",
        [0.1, 0.0, -0.1],
    ),
]
for name, desc, pattern in my_line_types:
    if name not in doc.linetypes:
        doc.linetypes.add(
            name=name,
            pattern=pattern,
            description=desc,
        )

Setup some predefined linetypes:

for name, desc, pattern in linetypes():
    if name not in doc.linetypes:
        doc.linetypes.add(
            name=name,
            pattern= pattern,
            description=desc,
        )

Check Available Linetypes

The linetypes object supports some standard Python protocols:

# iteration
print("available linetypes:")
for lt in doc.linetypes:
    print(f"{lt.dxf.name}: {lt.dxf.description}")

# check for existing linetype
if "DOTTED" in doc.linetypes:
    pass

count = len(doc.linetypes) # total count of linetypes

Removing Linetypes

Warning

Ezdxf does not check if a linetype is still in use and deleting a linetype which is still in use generates an invalid DXF file. The audit process audit() of the DXF document removes linetype attributes referencing non existing linetypes.

You can delete a linetype:

doc.layers.remove("DASHED")

This just removes the linetype definition, the linetype attribute of DXF entities may still refer the reoved linetype definition “DASHED” and AutoCAD will not open DXF files including undefined linetypes.

Tutorial for Complex Linetypes

In DXF R13 Autodesk introduced complex linetypes, containing TEXT or SHAPES in line types.

Complex linetype example with text:

../_images/ltype_text.jpg

Complex line type example with shapes:

../_images/ltype_shape.jpg

For easy usage the pattern string for complex line types is mostly the same string as the pattern definition strings in AutoCAD “.lin” files.

Example for complex line type TEXT:

doc = ezdxf.new("R2018")  # DXF R13 or later is required

doc.linetypes.add(
    name="GASLEITUNG2",
    # linetype definition string from acad.lin:
    pattern='A,.5,-.2,["GAS",STANDARD,S=.1,U=0.0,X=-0.1,Y=-.05],-.25',
    description= "Gasleitung2 ----GAS----GAS----GAS----GAS----GAS----",
    length=1,  # required for complex line types
})

The pattern always starts with an “A”, the following float values have the same meaning as for simple linetypes, a value > 0 is a line, a value < 0 is a gap, and a 0 is a point, the opening square bracket “[” starts the complex part of the linetype pattern.

The text after the “[” defines the complex linetype:

  • A text in quotes (e.g. “GAS”) defines a complex TEXT linetype and represents the pattern text itself.

  • A text without quotes is a SHAPE name (in “.lin” files) and defines a complex SHAPE linetype. Ezdxf can not translate this SHAPE name from the “.lin” file into the required shape file index, so *YOU have to translate this SHAPE name into the shape file index, e.g. saving the file with AutoCAD as DXF and searching for the DXF linetype definition, see example below and the DXF Internals: LTYPE Table.

For complex TEXT linetypes the second parameter is the text style, for complex SHAPE linetypes the second parameter is the shape file name, the shape file has to be in the same directory as the DXF file or in one of the CAD application support paths.

The meaning of the following comple linetype parameters are shown in the table below:

S

scaling factor, always > 0, if S=0 the TEXT or SHAPE is not visible

R or U

rotation relative to the line direction

X

x-direction offset (along the line)

Y

y-direction offset (perpendicular to the line)

These parameters are case insensitive and the closing square bracket “]” ends the complex part of the linetype pattern.

The fine tuning of this parameters is a try an error process, for complex TEXT linetypes the scaling factor (e.g. the STANDARD text style) sets the text height (e.g. “S=0.1” sets the text height to 0.1 units), by shifting in y-direction by half of the scaling factor, the text is vertically centered to the line. For the x-direction it seems to be a good practice to place a gap in front of the text and after the text, find x shifting value and gap sizes by try and error. The overall length is at least the sum of all line and gap definitions (absolute values).

Example for complex line type SHAPE:

doc.linetypes.add("GRENZE2",
    # linetype definition in acad.lin:
    # A,.25,-.1,[BOX,ltypeshp.shx,x=-.1,s=.1],-.1,1
    # replacing BOX by shape index 132 (got index from an AutoCAD file),
    # ezdxf can't get shape index from ltypeshp.shx
    pattern="A,.25,-.1,[132,ltypeshp.shx,x=-.1,s=.1],-.1,1",
    description="Grenze eckig ----[]-----[]----[]-----[]----[]--",
    length= 1.45,  # required for complex line types
})

Complex line types with shapes only work if the associated shape file (e. g. ltypeshp.shx) and the DXF file are in the same directory or the shape file is placed in one of the CAD application support folders.