Exporting PNG or PDF at a specific scale

[granludo]

Hi,
my program generates a DXF file of a guitar neck, I would like to print it to a PDF file at 1:1 scale.
But I just get a scaled version of my drawing to a random proportion I can't figure out.
Can somebody provide a suggestion?
Thanks
This is the code i use

import matplotlib.pyplot as plt
import matplotlib.style
import ezdxf
from ezdxf.addons.drawing import RenderContext, Frontend
from ezdxf.addons.drawing.matplotlib import MatplotlibBackend
#import wx
import glob
import re
import os
def convert_dxf2img( names, folder, img_format=default_img_format, img_res=default_img_res, clr=default_bg_color):
    for name in names:
        doc = ezdxf.readfile(name)
        msp = doc.modelspace()
        # Recommended: audit & repair DXF document before rendering
        auditor = doc.audit()
        # The auditor.errors attribute stores severe errors,
        # which *may* raise exceptions when rendering.
        if len(auditor.errors) != 0:
            raise Exception("This DXF document is damaged and can't be converted! --> ", name)
            name = name =+ 1
        else :
            cm = 1/2.54  # centimeters in inches
            plt.subplots(figsize=(500*cm, 2000*cm))
            fig = plt.figure()
            #fig = plt.figure(figsize=[40000, 40000])
            ax = fig.add_axes([0, 0, 1, 1])
            ctx = RenderContext(doc)
            ctx.set_current_layout(msp)
            ezdxf.addons.drawing.properties.MODEL_SPACE_BG_COLOR = clr
            out = MatplotlibBackend(ax)
            Frontend(ctx, out).draw_layout(msp, finalize=True)

            img_name = re.findall("(\S+)\.",name)  # select the image name that is the same as the dxf file name
            first_param = ''.join(img_name) + img_format  #concatenate list and string
            first_param=folder+os.path.basename(first_param)
            fig.savefig(first_param, dpi=img_res,size_inches= [500*cm, 2000*cm] )
            print(name," Converted Successfully")


`

[mozman]

I added an example how to render to a specific scale. This example does not support margins.

The following code is just an excerpt:

def save_to_scale(
    size_in_inches: tuple[float, float] = (8.5, 11),
    origin: tuple[float, float] = (0, 0),  # of modelspace area to render
    scale: float = 1,
    dpi: int = 300,
):
    doc = make_doc(offset=(1, 2), size=(6.5, 8))
    msp = doc.modelspace()

   ...

    ctx = RenderContext(doc)
    fig = plt.figure(dpi=dpi)
    ax = fig.add_axes([0, 0, 1, 1])

    # Get render limits in drawing units:
    min_x, min_y, max_x, max_y = render_limits(
        origin, size_in_inches, scale
    )

    ax.set_xlim(min_x, max_x)
    ax.set_ylim(min_y, max_y)

    out = MatplotlibBackend(ax)
    # Finalizing invokes auto-scaling by default!
    Frontend(ctx, out).draw_layout(msp, finalize=False)

    # Set output size in inches:
    fig.set_size_inches(size_in_inches[0], size_in_inches[1], forward=True)

    fig.savefig(DIR / f"image_scale_1_{scale}.pdf", dpi=dpi)
    plt.close(fig)

Define the render limits in inches:

def render_limits(
    origin: tuple[float, float],
    size_in_inches: tuple[float, float],
    scale: float,
) -> tuple[float, float, float, float]:
    """Returns the render limits in drawing units. """
    min_x, min_y = origin
    max_x = min_x + size_in_inches[0] * scale
    max_y = min_y + size_in_inches[1] * scale
    return min_x, min_y, max_x, max_y

For drawings in other base units a conversion is required e.g. mm to inch: size_in_inch = size_in_mm * (1/25.4)