eulumdat-plot

Photometric polar diagram generator for EULUMDAT (.ldt) files — designed for product datasheets and publication-ready documents.

Reads a .ldt file and produces a Lumtopic-style SVG: a square image with a top banner and a polar candela distribution diagram showing the C0/C180 (solid) and C90/C270 (dotted) curves, scaled to fill the plot area.

For scientific / interactive plots (matplotlib, axis labels, legends), see the eulumdat-py examples.

Part of the eulumdat-* ecosystem, built on top of eulumdat-py.

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Features

• Reads any EULUMDAT file — all symmetry types (ISYM 0–4) handled by eulumdat-py
• Generates a publication-ready SVG polar diagram (Lumtopic style)
• Dynamic radial scale (3–6 concentric circles, round values)
• Dominant-hemisphere detection for automatic scale label placement
• Proportional scaling via Layout.for_size(n) — one parameter controls everything
• Optional I(γ) interpolation (linear or cubic spline) for smooth curves
• Optional raster export to PNG and JPEG (cross-platform, no native DLL)
• Debug mode for visual validation of C-plane assignment

Installation

Core package (SVG generation only):

pip install eulumdat-plot

With raster export (PNG / JPEG):

pip install "eulumdat-plot[export]"

With cubic spline interpolation:

pip install "eulumdat-plot[cubic]"

Everything:

pip install "eulumdat-plot[full]"

Quick start

from eulumdat_plot import plot_ldt

# Generate an SVG next to the source file
svg = plot_ldt("luminaire.ldt")

# With a distribution code in the banner centre
svg = plot_ldt("luminaire.ldt", code="D53")

Scaling

All visual parameters (stroke widths, font sizes, margins) scale proportionally from the 1181 px reference with a single call:

from eulumdat_plot import plot_ldt, Layout

svg = plot_ldt("luminaire.ldt", layout=Layout.for_size(600))

Raster export

from eulumdat_plot import plot_ldt, Layout
from eulumdat_plot.export import svg_to_png, svg_to_jpg

svg = plot_ldt("luminaire.ldt", layout=Layout.for_size(1181))
png = svg_to_png(svg, size_px=600)
jpg = svg_to_jpg(svg, size_px=600, quality=95)

The export size is independent of the SVG canvas size.

API reference

plot_ldt()

def plot_ldt(
    ldt_path: str | Path,
    svg_path: str | Path | None = None,
    *,
    code: str = "",
    layout: Layout | None = None,
    interpolate: bool = True,
    interp_step_deg: float = 1.0,
    interp_method: str = "linear",
    debug: bool = False,
) -> Path

Parameter	Default	Description
ldt_path	—	Source .ldt file
svg_path	same name, .svg	Output SVG path
code	""	Distribution code shown in the banner centre
layout	Layout()	Visual parameters
interpolate	True	Resample I(γ) before plotting
interp_step_deg	1.0	Angular step for resampling (degrees)
interp_method	"linear"	"linear" or "cubic" (requires scipy)
debug	False	Colour-code C-planes for visual validation

Layout.for_size()

Layout.for_size(size_px: int) -> Layout

Creates a Layout with all dimensions scaled proportionally from the 1181 px reference. Layout.for_size(1181) is identical to Layout().

svg_to_png() / svg_to_jpg()

svg_to_png(svg_path, png_path=None, *, size_px=1181, background="#FFFFFF") -> Path
svg_to_jpg(svg_path, jpg_path=None, *, size_px=1181, background="#FFFFFF", quality=95) -> Path

Requires pip install "eulumdat-plot[export]".

Examples

File	Description
examples/01_basic_usage.md	Generate an SVG from a .ldt file
examples/02_resize_and_export.md	Scaling, raster export, batch processing

Project structure

eulumdat-plot/
├── data/
│   ├── input/          # sample .ldt files (ISYM 0–4)
│   └── output/         # generated SVG / PNG / JPEG
├── docs/
│   └── img/
│       └── sample_01.svg
├── examples/
│   ├── 01_basic_usage.md
│   └── 02_resize_and_export.md
├── src/
│   └── eulumdat_plot/
│       ├── __init__.py
│       ├── plot.py     # public API — LDT → SVG pipeline
│       ├── renderer.py # SVG renderer + Layout dataclass
│       └── export.py   # raster export (PNG / JPEG)
├── tests/
│   ├── test_smoke.py   # 46 real LDT files, all ISYM types
│   └── test_scaling.py # Layout.for_size() proportionality
├── pyproject.toml
├── CHANGELOG.md
└── README.md

EULUMDAT ecosystem

Package	Status	Description
eulumdat-py	v0.1.4	Read / write EULUMDAT files
eulumdat-symmetry	v1.0.0	Symmetrise EULUMDAT files
eulumdat-plot	v1.0.0	Photometric polar diagram — this package
eulumdat-luminance	planned	Luminance table cd/m² (γ 55°–85°)
eulumdat-ugr	planned	UGR calculation (CIE 117, CIE 190)

Requirements

• Python ≥ 3.9
• eulumdat-py ≥ 1.0.0
• numpy ≥ 1.21
• svgwrite ≥ 1.4
• (optional) vl-convert-python ≥ 1.6 + Pillow ≥ 9.0 — raster export
• (optional) scipy ≥ 1.7 — cubic spline interpolation

License

MIT — © 2024 123VincentB