feat(pygal): implement area-mountain-panorama (#5407)

## Implementation: `area-mountain-panorama` - python/pygal

Implements the **python/pygal** version of `area-mountain-panorama`.

**File:** `plots/area-mountain-panorama/implementations/python/pygal.py`

**Parent Issue:** #5365

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/24941215162)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

plots/area-mountain-panorama/implementations/python/pygal.py

@@ -0,0 +1,298 @@
+""" anyplot.ai
+area-mountain-panorama: Mountain Panorama Profile with Labeled Peaks
+Library: pygal 3.1.0 | Python 3.14.4
+Quality: 87/100 | Created: 2026-04-25
+"""
+
+import os
+import re
+import sys
+
+
+# Script filename shadows the installed `pygal` package when run as `python pygal.py`;
+# dropping the script directory from sys.path lets the real package resolve.
+sys.path.pop(0)
+
+import cairosvg  # noqa: E402
+import numpy as np  # noqa: E402
+import pygal  # noqa: E402
+from pygal.style import Style  # noqa: E402
+
+
+# Theme tokens
+THEME = os.getenv("ANYPLOT_THEME", "light")
+PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
+SKY_TOP = "#E8C8A0" if THEME == "light" else "#252D40"
+INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
+INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
+INK_MUTED = "#6B6A63" if THEME == "light" else "#A8A79F"
+BRAND = "#009E73"
+
+# Data — Wallis (Valais) summit panorama, ordered W → E
+peaks = [
+    ("Weisshorn", 12, 4506),
+    ("Zinalrothorn", 30, 4221),
+    ("Ober Gabelhorn", 45, 4063),
+    ("Dent Blanche", 58, 4358),
+    ("Dent d'Hérens", 76, 4171),
+    ("Matterhorn", 92, 4478),
+    ("Breithorn", 120, 4164),
+    ("Pollux", 132, 4092),
+    ("Castor", 139, 4223),
+    ("Liskamm", 152, 4527),
+    ("Monte Rosa", 170, 4634),
+    ("Strahlhorn", 192, 4190),
+    ("Rimpfischhorn", 204, 4199),
+    ("Allalinhorn", 215, 4027),
+    ("Alphubel", 225, 4206),
+    ("Täschhorn", 236, 4491),
+    ("Dom", 250, 4545),
+]
+
+# Skyline construction
+np.random.seed(42)
+angle = np.linspace(0, 262, 1200)
+
+# Base ridge: smoothed random walk in the 3000–3700 m belt (foothills + minor cols)
+walk = np.cumsum(np.random.randn(len(angle)) * 1.5)
+sigma_walk = 14
+g = np.arange(-3 * sigma_walk, 3 * sigma_walk + 1)
+kernel_walk = np.exp(-(g**2) / (2 * sigma_walk**2))
+walk = np.convolve(walk, kernel_walk / kernel_walk.sum(), mode="same")
+walk = (walk - walk.min()) / (walk.max() - walk.min())
+ridge = 3000 + walk * 700
+
+# Major summits as Gaussian peaks (max-combined for the visible silhouette)
+for _, pos, elev in peaks:
+    width = 5.5 + (elev - 4000) / 130
+    bump = (elev - 2700) * np.exp(-((angle - pos) ** 2) / (2 * width**2))
+    ridge = np.maximum(ridge, 2700 + bump)
+
+# Light final smoothing of the combined ridge
+sigma_ridge = 0.8
+g = np.arange(-3, 4)
+kernel_ridge = np.exp(-(g**2) / (2 * sigma_ridge**2))
+ridge = np.convolve(ridge, kernel_ridge / kernel_ridge.sum(), mode="same")
+
+# Canvas + plot box
+CANVAS_W, CANVAS_H = 4800, 2700
+MARGIN_L, MARGIN_R = 220, 120
+MARGIN_T, MARGIN_B = 200, 160
+
+Y_FLOOR, Y_CEIL = 2500, 6050
+X_MIN, X_MAX = 0, 262
+
+font = "DejaVu Sans, Helvetica, Arial, sans-serif"
+
+# Pygal Style — first colour is brand green; muted foreground used for axis chrome
+custom_style = Style(
+    background=PAGE_BG,
+    plot_background="transparent",
+    foreground=INK_SOFT,
+    foreground_strong=INK,
+    foreground_subtle=INK_MUTED,
+    colors=(BRAND, INK if THEME == "light" else "#F0EFE8"),
+    font_family=font,
+    title_font_family=font,
+    label_font_family=font,
+    major_label_font_family=font,
+    tooltip_font_family=font,
+    tooltip_font_size=30,
+    legend_font_size=34,
+    stroke_width=2,
+    opacity=".95",
+    opacity_hover=".75",
+    transition="200ms ease-in",
+)
+
+# Pygal XY chart with fill=True draws the ridge silhouette as the brand-green
+# series. Peak summits are added as a second non-stroked series so pygal
+# renders interactive hover dots over each named summit in the HTML export.
+chart = pygal.XY(
+    width=CANVAS_W,
+    height=CANVAS_H,
+    style=custom_style,
+    show_legend=False,
+    show_x_labels=False,
+    show_y_labels=False,
+    show_x_guides=False,
+    show_y_guides=False,
+    margin_left=MARGIN_L,
+    margin_right=MARGIN_R,
+    margin_top=MARGIN_T,
+    margin_bottom=MARGIN_B,
+    xrange=(X_MIN, X_MAX),
+    range=(Y_FLOOR, Y_CEIL),
+    fill=True,
+    show_dots=False,
+    stroke_style={"width": 2},
+    truncate_label=-1,
+)
+
+ridge_data = [{"value": (float(a), float(e))} for a, e in zip(angle, ridge, strict=True)]
+chart.add("Skyline", ridge_data)
+
+peak_data = [{"value": (float(pos), float(elev)), "label": f"{name} · {elev:,} m"} for name, pos, elev in peaks]
+chart.add("Peaks", peak_data, show_dots=True, dots_size=10, stroke=False, fill=False)
+
+# Render pygal first; back-compute its plot box from the two extreme summit dots
+# so post-processed chrome (sky gradient, leader lines, labels) aligns with the
+# interactive markers pygal drew.
+base_svg = chart.render(is_unicode=True)
+
+dot_re = re.compile(r'<circle cx="([-\d.]+)" cy="([-\d.]+)"[^>]*class="dot')
+dots = [(float(cx), float(cy)) for cx, cy in dot_re.findall(base_svg)]
+(p1x, p1y) = dots[0]
+(p2x, p2y) = dots[-1]
+ref_a, ref_b = peaks[0], peaks[-1]
+x_scale = (p2x - p1x) / (ref_b[1] - ref_a[1])
+x_off = p1x - ref_a[1] * x_scale
+y_scale = (p2y - p1y) / (ref_b[2] - ref_a[2])
+y_off = p1y - ref_a[2] * y_scale
+
+
+def to_svg(ax, ay):
+    return MARGIN_L + ax * x_scale + x_off, MARGIN_T + ay * y_scale + y_off
+
+
+plot_x_left, _ = to_svg(X_MIN, Y_CEIL)
+plot_x_right, plot_y_bottom = to_svg(X_MAX, Y_FLOOR)
+_, plot_y_top = to_svg(X_MIN, Y_CEIL)
+plot_w = plot_x_right - plot_x_left
+plot_h = plot_y_bottom - plot_y_top
+
+# Sky gradient + custom labels go BEFORE pygal's plot group so the silhouette
+# and interactive dots stay on top.
+svg_parts = [
+    f'<rect x="0" y="0" width="{CANVAS_W}" height="{CANVAS_H}" fill="{PAGE_BG}" stroke="none"/>',
+    f"""<defs>
+        <linearGradient id="skyGrad" x1="0" y1="0" x2="0" y2="1">
+            <stop offset="0%" stop-color="{SKY_TOP}"/>
+            <stop offset="100%" stop-color="{PAGE_BG}"/>
+        </linearGradient>
+    </defs>""",
+    f'<rect x="{plot_x_left:.2f}" y="{plot_y_top:.2f}" '
+    f'width="{plot_w:.2f}" height="{plot_h:.2f}" fill="url(#skyGrad)" stroke="none"/>',
+]
+
+# Title
+svg_parts.append(
+    f'<text x="{CANVAS_W / 2:.2f}" y="110" text-anchor="middle" fill="{INK}" '
+    f'style="font-size:62px;font-weight:500;font-family:{font}">'
+    f"Wallis Alps · area-mountain-panorama · pygal · anyplot.ai</text>"
+)
+
+# Y-axis title + tick labels (drawn manually since pygal labels are off)
+y_ticks = [3000, 3500, 4000, 4500, 5000, 5500, 6000]
+for v in y_ticks:
+    _, ty = to_svg(X_MIN, v)
+    svg_parts.append(
+        f'<text x="{plot_x_left - 28:.2f}" y="{ty + 14:.2f}" text-anchor="end" '
+        f'fill="{INK_SOFT}" style="font-size:36px;font-family:{font}">{v:,}</text>'
+    )
+    svg_parts.append(
+        f'<line x1="{plot_x_left:.2f}" y1="{ty:.2f}" x2="{plot_x_right:.2f}" y2="{ty:.2f}" '
+        f'stroke="{INK}" stroke-opacity="0.10" stroke-width="1.2"/>'
+    )
+
+y_title_x = plot_x_left - 140
+y_title_y = plot_y_top + plot_h / 2
+svg_parts.append(
+    f'<text x="{y_title_x:.2f}" y="{y_title_y:.2f}" text-anchor="middle" fill="{INK}" '
+    f'style="font-size:42px;font-family:{font}" '
+    f'transform="rotate(-90, {y_title_x:.2f}, {y_title_y:.2f})">Elevation (m)</text>'
+)
+
+# Compass bearings on x-axis
+compass_ticks = [(10, "W"), (65, "SW"), (120, "S"), (180, "SE"), (245, "E")]
+for ang, label in compass_ticks:
+    tx, _ = to_svg(ang, Y_FLOOR)
+    svg_parts.append(
+        f'<text x="{tx:.2f}" y="{plot_y_bottom + 60:.2f}" text-anchor="middle" '
+        f'fill="{INK_SOFT}" style="font-size:36px;font-family:{font}">{label}</text>'
+    )
+
+# L-shaped frame (left + bottom)
+svg_parts.append(
+    f'<line x1="{plot_x_left:.2f}" y1="{plot_y_top:.2f}" x2="{plot_x_left:.2f}" y2="{plot_y_bottom:.2f}" '
+    f'stroke="{INK_SOFT}" stroke-width="2"/>'
+)
+svg_parts.append(
+    f'<line x1="{plot_x_left:.2f}" y1="{plot_y_bottom:.2f}" x2="{plot_x_right:.2f}" y2="{plot_y_bottom:.2f}" '
+    f'stroke="{INK_SOFT}" stroke-width="2"/>'
+)
+
+# Peak labels — staggered across three vertical tiers, with thin leader lines.
+# Matterhorn is treated as the focal anchor (heavier weight + colour).
+LABEL_TIERS = [4870, 5180, 5490]
+for i, (name, pos, elev) in enumerate(peaks):
+    is_focal = name == "Matterhorn"
+    tier_y_data = LABEL_TIERS[i % 3]
+    sx, sy_summit = to_svg(pos, elev)
+    _, sy_label = to_svg(pos, tier_y_data)
+
+    leader_color = INK if is_focal else INK_SOFT
+    leader_op = 0.85 if is_focal else 0.45
+    leader_w = 2.0 if is_focal else 1.2
+
+    svg_parts.append(
+        f'<line x1="{sx:.2f}" y1="{sy_summit - 6:.2f}" x2="{sx:.2f}" y2="{sy_label + 18:.2f}" '
+        f'stroke="{leader_color}" stroke-opacity="{leader_op}" stroke-width="{leader_w}"/>'
+    )
+
+    name_size = 34 if is_focal else 28
+    elev_size = 26 if is_focal else 22
+    name_weight = "700" if is_focal else "600"
+    name_color = INK if is_focal else INK_SOFT
+    elev_color = INK_SOFT if is_focal else INK_MUTED
+
+    svg_parts.append(
+        f'<text x="{sx:.2f}" y="{sy_label:.2f}" text-anchor="middle" fill="{name_color}" '
+        f'style="font-size:{name_size}px;font-weight:{name_weight};font-family:{font}">{name}</text>'
+    )
+    svg_parts.append(
+        f'<text x="{sx:.2f}" y="{sy_label + name_size + 6:.2f}" text-anchor="middle" fill="{elev_color}" '
+        f'style="font-size:{elev_size}px;font-family:{font}">{elev:,} m</text>'
+    )
+
+# Subtitle
+svg_parts.append(
+    f'<text x="{CANVAS_W / 2:.2f}" y="170" text-anchor="middle" fill="{INK_SOFT}" '
+    f'style="font-size:32px;font-family:{font}">'
+    f"Sixteen 4 000 m peaks of the Pennine Alps, viewed W → E from a single vantage</text>"
+)
+
+custom_svg = "\n".join(svg_parts)
+
+# Inject the custom chrome BEFORE pygal's plot group so the silhouette and
+# interactive markers stay layered on top of the sky gradient.
+plot_group_idx = base_svg.find('class="plot"')
+if plot_group_idx != -1:
+    insert_idx = base_svg.rfind("<g", 0, plot_group_idx)
+    output_svg = base_svg[:insert_idx] + custom_svg + "\n" + base_svg[insert_idx:]
+else:
+    output_svg = base_svg.replace("</svg>", f"{custom_svg}\n</svg>")
+
+cairosvg.svg2png(bytestring=output_svg.encode("utf-8"), write_to=f"plot-{THEME}.png", output_width=CANVAS_W)
+
+html_content = f"""<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <title>area-mountain-panorama · pygal · anyplot.ai</title>
+    <style>
+        body {{ margin: 0; background: {PAGE_BG}; display: flex;
+                justify-content: center; align-items: center; min-height: 100vh; }}
+        .chart {{ max-width: 100%; height: auto; }}
+    </style>
+</head>
+<body>
+    <figure class="chart">
+        {output_svg}
+    </figure>
+</body>
+</html>
+"""
+
+with open(f"plot-{THEME}.html", "w", encoding="utf-8") as f:
+    f.write(html_content)