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# Copyright (c) 2020, Matthew Broadway, https://github.com/mozman/ezdxf/discussions/219
# Copyright (c) 2022, Manfred Moitzi
# License: MIT License
from __future__ import annotations
import pathlib
import matplotlib.pyplot as plt
from PIL import Image, ImageDraw
import ezdxf
from ezdxf.math import Matrix44
from ezdxf.addons.drawing import RenderContext, Frontend
from ezdxf.addons.drawing.matplotlib import MatplotlibBackend
CWD = pathlib.Path("~/Desktop/Outbox").expanduser()
if not CWD.exists():
CWD = pathlib.Path(".")
def get_wcs_to_image_transform(
ax: plt.Axes, image_size: tuple[int, int]
) -> Matrix44:
"""Returns the transformation matrix from modelspace coordinates to image
coordinates.
"""
x1, x2 = ax.get_xlim()
y1, y2 = ax.get_ylim()
data_width, data_height = x2 - x1, y2 - y1
image_width, image_height = image_size
return (
Matrix44.translate(-x1, -y1, 0)
@ Matrix44.scale(
image_width / data_width, -image_height / data_height, 1.0
)
# +1 to counteract the effect of the pixels being flipped in y
@ Matrix44.translate(0, image_height + 1, 0)
)
def get_image_to_wcs_transform(
ax: plt.Axes, image_size: tuple[int, int]
) -> Matrix44:
"""Returns the transformation matrix from image coordinates to modelspace
coordinates.
"""
m = get_wcs_to_image_transform(ax, image_size)
m.inverse()
return m
def main():
# create the DXF document
doc = ezdxf.new()
msp = doc.modelspace()
msp.add_lwpolyline([(0, 0), (1, 0), (1, 1), (0, 1)], close=True)
msp.add_line((0, 0), (1, 1))
# export the pixel image
fig: plt.Figure = plt.figure()
ax: plt.Axes = fig.add_axes([0, 0, 1, 1])
ctx = RenderContext(doc)
out = MatplotlibBackend(ax)
Frontend(ctx, out).draw_layout(msp, finalize=True)
fig.savefig(CWD / "cad.png")
plt.close(fig)
# reload the pixel image by Pillow (PIL)
img = Image.open(CWD / "cad.png")
draw = ImageDraw.Draw(img)
# add some annotations to the pixel image by using modelspace coordinates
m = get_wcs_to_image_transform(ax, img.size)
a, b, c = (
(v.x, v.y) # draw.line() expects tuple[float, float] as coordinates
# transform modelspace coordinates to image coordinates
for v in m.transform_vertices([(0.25, 0.75), (0.75, 0.25), (1, 1)])
)
draw.line([a, b, c, a], fill=(255, 0, 0))
# show the image by the default image viewer
img.show()
# convert pixel coordinates to modelspace coordinates
img2wcs = get_image_to_wcs_transform(ax, img.size)
print(f"0.25, 0.75 == {img2wcs.transform(a).round(2)}")
print(f"0.75, 0.25 == {img2wcs.transform(b).round(2)}")
print(f"1.00, 1.00 == {img2wcs.transform(c).round(2)}")
if __name__ == "__main__":
main()
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