src/utils.py

import math
import ezdxf
import matplotlib.pyplot as plt
from matplotlib.patches import Circle, Arc


def render_dxf_layer_to_png(
    doc: object,
    layer_name: str,
    output_path: str = "layer.png",
    dpi: int = 300,
    line_width: float = 1.0,
    padding_ratio: float = 0.05,
):
    msp = doc.modelspace()

    fig, ax = plt.subplots()

    xs = []
    ys = []

    def update_bounds(x, y):
        xs.append(x)
        ys.append(y)

    for e in msp:
        if e.dxf.layer != layer_name:
            continue

        etype = e.dxftype()

        if etype == "LINE":
            x1, y1 = e.dxf.start.x, e.dxf.start.y
            x2, y2 = e.dxf.end.x, e.dxf.end.y
            ax.plot([x1, x2], [y1, y2], linewidth=line_width)
            update_bounds(x1, y1)
            update_bounds(x2, y2)

        elif etype == "LWPOLYLINE":
            pts = [(p[0], p[1]) for p in e.get_points()]
            if len(pts) >= 2:
                x = [p[0] for p in pts]
                y = [p[1] for p in pts]
                if e.closed:
                    x.append(pts[0][0])
                    y.append(pts[0][1])
                ax.plot(x, y, linewidth=line_width)
                for px, py in pts:
                    update_bounds(px, py)

        elif etype == "POLYLINE":
            pts = [(v.dxf.location.x, v.dxf.location.y) for v in e.vertices]
            if len(pts) >= 2:
                x = [p[0] for p in pts]
                y = [p[1] for p in pts]
                if e.is_closed:
                    x.append(pts[0][0])
                    y.append(pts[0][1])
                ax.plot(x, y, linewidth=line_width)
                for px, py in pts:
                    update_bounds(px, py)

        elif etype == "CIRCLE":
            cx, cy = e.dxf.center.x, e.dxf.center.y
            r = e.dxf.radius
            patch = Circle((cx, cy), r, fill=False, linewidth=line_width)
            ax.add_patch(patch)
            update_bounds(cx - r, cy - r)
            update_bounds(cx + r, cy + r)

        elif etype == "ARC":
            cx, cy = e.dxf.center.x, e.dxf.center.y
            r = e.dxf.radius
            start_angle = e.dxf.start_angle
            end_angle = e.dxf.end_angle

            patch = Arc(
                (cx, cy),
                width=2 * r,
                height=2 * r,
                angle=0,
                theta1=start_angle,
                theta2=end_angle,
                linewidth=line_width,
            )
            ax.add_patch(patch)

            # バウンディング更新は簡易的に円全体で取る
            update_bounds(cx - r, cy - r)
            update_bounds(cx + r, cy + r)

    if not xs or not ys:
        raise ValueError(f"Layer '{layer_name}' に描画対象がありません")

    min_x, max_x = min(xs), max(xs)
    min_y, max_y = min(ys), max(ys)

    dx = max_x - min_x
    dy = max_y - min_y
    pad_x = max(dx * padding_ratio, 1e-6)
    pad_y = max(dy * padding_ratio, 1e-6)

    ax.set_xlim(min_x - pad_x, max_x + pad_x)
    ax.set_ylim(min_y - pad_y, max_y + pad_y)
    ax.set_aspect("equal", adjustable="box")
    ax.axis("off")

    plt.savefig(output_path, dpi=dpi, bbox_inches="tight", pad_inches=0)
    plt.close(fig)


if __name__ == "__main__":
    render_dxf_layer_to_png(
        dxf_path="input.dxf",
        layer_name="MY_LAYER",
        output_path="layer.png",
    )