feat(bokeh): implement contour-basic (#5330)

## Implementation: `contour-basic` - python/bokeh

Implements the **python/bokeh** version of `contour-basic`.

**File:** `plots/contour-basic/implementations/python/bokeh.py`

**Parent Issue:** #855

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/24867170776)*

---------

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/contour-basic/implementations/python/bokeh.py

@@ -1,144 +1,110 @@
-""" pyplots.ai
+""" anyplot.ai
 contour-basic: Basic Contour Plot
-Library: bokeh 3.8.1 | Python 3.13.11
-Quality: 91/100 | Created: 2025-12-23
+Library: bokeh 3.9.0 | Python 3.14.4
+Quality: 90/100 | Updated: 2026-04-24
 """
 
+import os
+
 import numpy as np
-from bokeh.io import export_png, save
-from bokeh.models import BasicTicker, ColorBar, LinearColorMapper
+from bokeh.io import export_png, output_file, save
 from bokeh.palettes import Viridis256
 from bokeh.plotting import figure
-from bokeh.resources import CDN
-from contourpy import contour_generator
 
 
-# Data - create a 2D scalar field using a mathematical function
-np.random.seed(42)
-x = np.linspace(-3, 3, 50)
-y = np.linspace(-3, 3, 50)
+THEME = os.getenv("ANYPLOT_THEME", "light")
+PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
+ELEVATED_BG = "#FFFDF6" if THEME == "light" else "#242420"
+INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
+INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
+
+# Data — simulated topographic elevation map of a 10km x 10km mountain region
+x = np.linspace(0, 10, 90)
+y = np.linspace(0, 10, 90)
 X, Y = np.meshgrid(x, y)
 
-# Create a Gaussian peak function with primary and secondary peaks
-# This shows contour features: nested rings, gradient directions, multiple maxima
-Z = np.exp(-(X**2 + Y**2)) + 0.5 * np.exp(-((X - 1.5) ** 2 + (Y + 1) ** 2) / 0.5)
-
-# Define contour levels for smooth gradient visualization
-levels = np.linspace(Z.min(), Z.max(), 12)
-
-# Map levels to colors from Viridis palette (colorblind-safe)
-n_levels = len(levels) - 1
-color_indices = [int(i * 255 / (n_levels - 1)) if n_levels > 1 else 0 for i in range(n_levels)]
-level_colors = [Viridis256[idx] for idx in color_indices]
-
-# Generate filled contours using contourpy
-fill_xs = []
-fill_ys = []
-fill_colors = []
-
-for i in range(len(levels) - 1):
-    low_level = levels[i]
-    high_level = levels[i + 1]
-
-    # Create filled contour generator
-    cont_gen = contour_generator(x=x, y=y, z=Z, fill_type="ChunkCombinedOffset")
-    filled = cont_gen.filled(low_level, high_level)
-
-    # ChunkCombinedOffset returns tuple of (points_list, offsets_list) per chunk
-    points_list, offsets_list = filled
-
-    # Process each chunk
-    for chunk_idx in range(len(points_list)):
-        points = points_list[chunk_idx]
-        offsets = offsets_list[chunk_idx]
-
-        if points is None or offsets is None:
-            continue
-
-        # Extract polygons using offset pairs
-        for j in range(len(offsets) - 1):
-            start = int(offsets[j])
-            end = int(offsets[j + 1])
-            polygon = points[start:end]
-            if len(polygon) > 2:
-                fill_xs.append(polygon[:, 0].tolist())
-                fill_ys.append(polygon[:, 1].tolist())
-                fill_colors.append(level_colors[i])
-
-# Generate contour lines using contourpy
-line_xs = []
-line_ys = []
-
-cont_gen_lines = contour_generator(x=x, y=y, z=Z, line_type="SeparateCode")
-for level in levels:
-    lines, codes = cont_gen_lines.lines(level)
-    for line in lines:
-        if len(line) > 1:
-            line_xs.append(line[:, 0].tolist())
-            line_ys.append(line[:, 1].tolist())
-
-# Create Bokeh figure
+elevation = (
+    850 * np.exp(-((X - 7) ** 2 + (Y - 7) ** 2) / 4.0)
+    + 550 * np.exp(-((X - 2.5) ** 2 + (Y - 3) ** 2) / 3.0)
+    - 180 * np.exp(-((X - 5) ** 2 + (Y - 5) ** 2) / 8.0)
+    + 12 * X
+    + 350
+)
+
+levels = np.linspace(elevation.min(), elevation.max(), 14)
+
+# Plot
 p = figure(
     width=4800,
     height=2700,
-    title="contour-basic · bokeh · pyplots.ai",
-    x_axis_label="X Coordinate",
-    y_axis_label="Y Coordinate",
+    title="Mountain Terrain · contour-basic · bokeh · anyplot.ai",
+    x_axis_label="Distance East (km)",
+    y_axis_label="Distance North (km)",
     toolbar_location=None,
-    tools="",
-    x_range=(-3.2, 3.2),
-    y_range=(-3.2, 3.2),
+    x_range=(0, 10),
+    y_range=(0, 10),
+    match_aspect=True,
 )
 
-# Plot filled contours
-if fill_xs:
-    p.patches(xs=fill_xs, ys=fill_ys, fill_color=fill_colors, line_color=None, fill_alpha=0.9)
-
-# Plot contour lines
-if line_xs:
-    p.multi_line(xs=line_xs, ys=line_ys, line_color="#333333", line_width=1.5, line_alpha=0.7)
-
-# Add color bar
-color_mapper = LinearColorMapper(palette=Viridis256, low=Z.min(), high=Z.max())
-color_bar = ColorBar(
-    color_mapper=color_mapper,
-    ticker=BasicTicker(desired_num_ticks=10),
-    label_standoff=16,
-    major_label_text_font_size="18pt",
+contour = p.contour(
+    x=X, y=Y, z=elevation, levels=levels, fill_color=Viridis256, line_color=PAGE_BG, line_width=2, line_alpha=0.45
+)
+
+colorbar = contour.construct_color_bar(
+    title="Elevation (m)",
+    title_text_font_size="26pt",
+    title_text_color=INK,
+    title_text_font_style="normal",
+    title_standoff=20,
+    major_label_text_font_size="22pt",
+    major_label_text_color=INK_SOFT,
+    background_fill_color=PAGE_BG,
     border_line_color=None,
-    location=(0, 0),
-    width=40,
-    title="Z Value",
-    title_text_font_size="20pt",
+    width=60,
+    padding=20,
 )
-p.add_layout(color_bar, "right")
-
-# Styling for 4800x2700 px
-p.title.text_font_size = "28pt"
-p.xaxis.axis_label_text_font_size = "22pt"
-p.yaxis.axis_label_text_font_size = "22pt"
-p.xaxis.major_label_text_font_size = "18pt"
-p.yaxis.major_label_text_font_size = "18pt"
-
-# Grid styling - subtle
-p.xgrid.grid_line_color = "#cccccc"
-p.ygrid.grid_line_color = "#cccccc"
-p.xgrid.grid_line_alpha = 0.3
-p.ygrid.grid_line_alpha = 0.3
-p.xgrid.grid_line_dash = [6, 4]
-p.ygrid.grid_line_dash = [6, 4]
-
-# Axis styling
-p.axis.axis_line_color = "#666666"
-p.axis.major_tick_line_color = "#666666"
-
-# Background
-p.background_fill_color = "#fafafa"
-p.border_fill_color = "white"
+p.add_layout(colorbar, "right")
+
+# Typography — sized for 4800×2700 canvas
+p.title.text_font_size = "42pt"
+p.title.text_font_style = "bold"
+p.title.text_color = INK
+p.title.align = "center"
+
+p.xaxis.axis_label_text_font_size = "32pt"
+p.yaxis.axis_label_text_font_size = "32pt"
+p.xaxis.axis_label_text_font_style = "normal"
+p.yaxis.axis_label_text_font_style = "normal"
+p.xaxis.major_label_text_font_size = "24pt"
+p.yaxis.major_label_text_font_size = "24pt"
+p.xaxis.axis_label_standoff = 28
+p.yaxis.axis_label_standoff = 28
+
+# Theme-adaptive chrome
+p.background_fill_color = PAGE_BG
+p.border_fill_color = PAGE_BG
 p.outline_line_color = None
-
-# Save PNG
-export_png(p, filename="plot.png")
-
-# Save HTML for interactive version
-save(p, filename="plot.html", resources=CDN, title="contour-basic · bokeh · pyplots.ai")
+p.min_border_right = 60
+
+p.xaxis.axis_label_text_color = INK
+p.yaxis.axis_label_text_color = INK
+p.xaxis.major_label_text_color = INK_SOFT
+p.yaxis.major_label_text_color = INK_SOFT
+p.xaxis.axis_line_color = INK_SOFT
+p.yaxis.axis_line_color = INK_SOFT
+p.xaxis.major_tick_line_color = INK_SOFT
+p.yaxis.major_tick_line_color = INK_SOFT
+p.xaxis.minor_tick_line_color = None
+p.yaxis.minor_tick_line_color = None
+
+# Filled contour covers the plot area, so disable grid to avoid noise
+p.xgrid.grid_line_color = None
+p.ygrid.grid_line_color = None
+
+p.xaxis.ticker.desired_num_ticks = 10
+p.yaxis.ticker.desired_num_ticks = 8
+
+# Save
+export_png(p, filename=f"plot-{THEME}.png")
+output_file(f"plot-{THEME}.html", title="contour-basic · bokeh · anyplot.ai")
+save(p)