🎨 assets: add a logo, one plotting call dispatched to three backends

docs/_static/make_logo.py

@@ -0,0 +1,102 @@
+# /// script
+# requires-python = ">=3.11"
+# dependencies = ["resvg-py"]
+# ///
+"""Draw the plotting_backends logo: one plotting call, three backends.
+
+A dot, the plotting call, branching to three small charts. Each shows the same
+plot, drawn by a different backend in its own colour. The shapes are vector, so
+the logo is written as an SVG, sharp at any size; for a bitmap, name a .png and
+give its size::
+
+    uv run docs/_static/make_logo.py                     # favicon.svg
+    uv run docs/_static/make_logo.py --size 2048 big.png
+"""
+
+import argparse
+from pathlib import Path
+
+NAVY = "#030a23"  # GalacticDynamics' navy
+BACKENDS = ("#66a19a", "#4fb8e8", "#7738eb")  # each backend's colour, top first
+
+# In a 64-unit square: the call's centre and radius, and each chart's left x,
+# its side, and the top y of each.
+CALL = (12, 32, 6)
+CHART_X, CHART_SIZE, CHART_TOPS = 36, 16, (4, 24, 44)
+# The plot every backend draws, as points in its chart: 0-1 across, 0-1 down.
+PLOT = ((0.15, 0.78), (0.4, 0.42), (0.62, 0.6), (0.86, 0.18))
+
+SVG = """\
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64" width="512" height="512">
+  <circle cx="{cx:g}" cy="{cy:g}" r="{cr:g}" fill="{navy}"/>
+  <g fill="none" stroke-linecap="round" stroke-linejoin="round">
+{branches}
+{charts}
+  </g>
+</svg>
+"""
+
+
+def chart(top: float, colour: str) -> str:
+    """Return one backend's chart: a frame, and the plot in ``colour``."""
+    x, s = CHART_X, CHART_SIZE
+    line = "L".join(f"{x + u * s:.2f} {top + v * s:.2f}" for u, v in PLOT)
+    return (
+        f'    <rect x="{x:g}" y="{top:g}" width="{s:g}" height="{s:g}" rx="2.5"'
+        f' fill="#fff" stroke="{NAVY}" stroke-width="2"/>\n'
+        f'    <path d="M{line}" stroke="{colour}" stroke-width="2.4"/>'
+    )
+
+
+def svg() -> str:
+    """Return the logo as SVG text."""
+    cx, cy, cr = CALL
+    middle = CHART_SIZE / 2
+    branches = "\n".join(
+        f'    <path d="M{cx + cr:g} {cy:g}C{cx + 16:g} {cy:g} {cx + 14:g}'
+        f' {top + middle:g} {CHART_X - 2:g} {top + middle:g}"'
+        f' stroke="{NAVY}" stroke-width="2.4"/>'
+        for top in CHART_TOPS
+    )
+    charts = "\n".join(
+        chart(top, colour) for top, colour in zip(CHART_TOPS, BACKENDS, strict=True)
+    )
+    return SVG.format(
+        cx=cx,
+        cy=cy,
+        cr=cr,
+        navy=NAVY,
+        branches=branches,
+        charts=charts,
+    )
+
+
+def main() -> None:
+    """Parse the command line and save the logo."""
+    parser = argparse.ArgumentParser(description=__doc__.split("\n")[0])
+    parser.add_argument(
+        "out",
+        nargs="?",
+        type=Path,
+        default=Path(__file__).with_name("favicon.svg"),
+        help="output file, SVG or PNG by its extension (default: favicon.svg)",
+    )
+    parser.add_argument(
+        "--size",
+        type=int,
+        default=512,
+        help="pixels per side, for a PNG",
+    )
+    args = parser.parse_args()
+
+    if args.out.suffix == ".svg":
+        args.out.write_text(svg())
+    else:
+        import resvg_py  # noqa: PLC0415  # only a PNG needs a renderer
+
+        png = resvg_py.svg_to_bytes(svg_string=svg(), width=args.size)
+        args.out.write_bytes(bytes(png))
+
+
+if __name__ == "__main__":
+    main()