feat(pygal): implement heatmap-stripes-climate

plots/heatmap-stripes-climate/implementations/pygal.py

@@ -0,0 +1,169 @@
+""" pyplots.ai
+heatmap-stripes-climate: Climate Warming Stripes
+Library: pygal 3.1.0 | Python 3.14.3
+Quality: 87/100 | Created: 2026-03-06
+"""
+
+import importlib
+import re
+import sys
+
+import numpy as np
+
+
+# Avoid importing this file instead of the pygal package
+_script_dir = sys.path[0]
+sys.path.remove(_script_dir)
+pygal = importlib.import_module("pygal")
+Style = importlib.import_module("pygal.style").Style
+cairosvg = importlib.import_module("cairosvg")
+sys.path.insert(0, _script_dir)
+
+# Data - Simulated global temperature anomalies (relative to 1961-1990 baseline)
+np.random.seed(42)
+years = list(range(1850, 2025))
+n_years = len(years)
+
+base_trend = np.concatenate(
+    [
+        np.linspace(-0.35, -0.15, 50),
+        np.linspace(-0.15, -0.25, 30),
+        np.linspace(-0.25, -0.05, 30),
+        np.linspace(-0.05, 0.30, 25),
+        np.linspace(0.30, 1.20, 40),
+    ]
+)
+noise = np.random.normal(0, 0.10, n_years)
+anomalies = np.round(base_trend + noise, 2)
+
+# Color scale symmetric around zero
+vmax = float(np.percentile(np.abs(anomalies), 90))
+vmin = -vmax
+
+# Diverging blue-to-red color stops (Ed Hawkins warming stripes palette)
+COLOR_STOPS = [
+    (0.00, (8, 48, 107)),
+    (0.12, (33, 102, 172)),
+    (0.25, (67, 147, 195)),
+    (0.42, (146, 197, 222)),
+    (0.50, (245, 245, 245)),
+    (0.58, (244, 165, 130)),
+    (0.75, (214, 96, 77)),
+    (0.88, (178, 24, 43)),
+    (1.00, (103, 0, 13)),
+]
+
+# Map each anomaly to a hex color via piecewise linear interpolation
+bar_colors = []
+for a in anomalies:
+    t = max(0.0, min(1.0, (a - vmin) / (vmax - vmin)))
+    r, g, b = COLOR_STOPS[-1][1]
+    for k in range(len(COLOR_STOPS) - 1):
+        t0, c0 = COLOR_STOPS[k]
+        t1, c1 = COLOR_STOPS[k + 1]
+        if t <= t1:
+            f = (t - t0) / (t1 - t0) if t1 > t0 else 0
+            r = int(c0[0] + (c1[0] - c0[0]) * f)
+            g = int(c0[1] + (c1[1] - c0[1]) * f)
+            b = int(c0[2] + (c1[2] - c0[2]) * f)
+            break
+    bar_colors.append(f"#{r:02x}{g:02x}{b:02x}")
+
+# Pygal style - minimal chrome, larger title for 4800px canvas
+custom_style = Style(
+    background="white",
+    plot_background="white",
+    foreground="#333333",
+    foreground_strong="#222222",
+    foreground_subtle="#cccccc",
+    colors=("#306998",),
+    title_font_size=48,
+    label_font_size=24,
+    major_label_font_size=28,
+    value_font_size=14,
+    font_family="sans-serif",
+)
+
+# Create chart - 3:1 aspect ratio per spec for horizontal time emphasis
+chart = pygal.Bar(
+    width=4800,
+    height=1600,
+    style=custom_style,
+    title="heatmap-stripes-climate \u00b7 pygal \u00b7 pyplots.ai",
+    show_legend=False,
+    show_y_guides=False,
+    show_x_guides=False,
+    show_y_labels=False,
+    show_x_labels=True,
+    margin=0,
+    margin_top=120,
+    margin_bottom=140,
+    margin_left=10,
+    margin_right=10,
+    spacing=0,
+    print_values=False,
+    range=(0, 1),
+    stroke=False,
+    truncate_label=-1,
+)
+
+# Only show first and last year labels for minimal design
+chart.x_labels = [str(y) if y in (years[0], years[-1]) else "" for y in years]
+chart.add("Temperature Anomaly", [{"value": 1, "color": bar_colors[i]} for i in range(n_years)])
+
+# Render SVG, strip axis lines pygal draws by default (no API to disable)
+svg_str = chart.render(is_unicode=True)
+svg_str = re.sub(r'<path[^>]*class="line"[^>]*/>', "", svg_str)
+cairosvg.svg2png(bytestring=svg_str.encode("utf-8"), write_to="plot.png")
+
+# Interactive HTML version with year tooltips (leverages pygal SVG strengths)
+html_chart = pygal.Bar(
+    width=4800,
+    height=1600,
+    style=custom_style,
+    title="heatmap-stripes-climate \u00b7 pygal \u00b7 pyplots.ai",
+    show_legend=False,
+    show_y_guides=False,
+    show_x_guides=False,
+    show_y_labels=False,
+    show_x_labels=True,
+    margin=0,
+    margin_top=120,
+    margin_bottom=140,
+    margin_left=10,
+    margin_right=10,
+    spacing=0,
+    print_values=False,
+    range=(0, 1),
+    stroke=False,
+    truncate_label=-1,
+)
+html_chart.x_labels = [str(y) for y in years]
+html_chart.x_labels_major = [str(y) for y in years if y % 25 == 0]
+html_chart.show_minor_x_labels = False
+html_chart.add(
+    "Temperature Anomaly",
+    [{"value": 1, "color": bar_colors[i], "label": f"{years[i]}: {anomalies[i]:+.2f}\u00b0C"} for i in range(n_years)],
+)
+
+html_content = f"""<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <title>heatmap-stripes-climate - pygal</title>
+    <style>
+        body {{ margin: 0; display: flex; justify-content: center; align-items: center;
+               min-height: 100vh; background: #f5f5f5; }}
+        .chart {{ max-width: 100%; height: auto; }}
+    </style>
+</head>
+<body>
+    <figure class="chart">
+        {html_chart.render(is_unicode=True)}
+    </figure>
+</body>
+</html>
+"""
+
+with open("plot.html", "w", encoding="utf-8") as fout:
+    fout.write(html_content)