feat(pygal): implement venn-basic (#2495)

github-actions[bot] · claude · web-flow · commit 803e83dc20e4 · 2025-12-29T23:48:31.000Z
## Implementation: `venn-basic` - pygal Implements the **pygal** version of `venn-basic`. **File:** `plots/venn-basic/implementations/pygal.py` --- :robot: *[impl-generate workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20584842103)* --------- Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com> Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com> Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
diff --git a/plots/venn-basic/implementations/pygal.py b/plots/venn-basic/implementations/pygal.py
@@ -0,0 +1,157 @@
+""" pyplots.ai
+venn-basic: Venn Diagram
+Library: pygal 3.1.0 | Python 3.13.11
+Quality: 78/100 | Created: 2025-12-29
+"""
+
+import cairosvg
+import numpy as np
+import pygal
+from pygal.style import Style
+
+
+# Data: Three product categories with overlapping features
+set_labels = ["Product A", "Product B", "Product C"]
+set_sizes = [100, 80, 60]
+
+# Overlaps: AB=30, AC=20, BC=25, ABC=10
+ab_overlap = 30
+ac_overlap = 20
+bc_overlap = 25
+abc_overlap = 10
+
+# Calculate exclusive regions
+only_a = set_sizes[0] - ab_overlap - ac_overlap + abc_overlap  # 60
+only_b = set_sizes[1] - ab_overlap - bc_overlap + abc_overlap  # 35
+only_c = set_sizes[2] - ac_overlap - bc_overlap + abc_overlap  # 25
+only_ab = ab_overlap - abc_overlap  # 20
+only_ac = ac_overlap - abc_overlap  # 10
+only_bc = bc_overlap - abc_overlap  # 15
+
+# Custom style for Venn diagram (scaled for 3600x3600 canvas)
+custom_style = Style(
+    background="white",
+    plot_background="white",
+    foreground="#333333",
+    foreground_strong="#333333",
+    foreground_subtle="#666666",
+    colors=("#306998", "#FFD43B", "#4CAF50"),  # Python Blue, Python Yellow, Green
+    opacity=0.4,
+    opacity_hover=0.5,
+    title_font_size=56,
+    legend_font_size=44,  # Increased legend font size for better visibility
+    label_font_size=28,
+    major_label_font_size=24,
+    value_font_size=32,
+    stroke_width=4,
+)
+
+# Create XY chart with larger margins to prevent label cut-off
+chart = pygal.XY(
+    width=3600,
+    height=3600,
+    style=custom_style,
+    fill=True,
+    stroke=True,
+    show_dots=False,
+    show_legend=True,
+    legend_at_bottom=True,
+    legend_box_size=36,  # Larger legend box for better visibility
+    title="venn-basic · pygal · pyplots.ai",
+    show_x_guides=False,
+    show_y_guides=False,
+    show_x_labels=False,
+    show_y_labels=False,
+    x_title=None,
+    y_title=None,
+    margin=250,  # Larger margin to prevent label and circle cut-off
+    spacing=15,
+    explicit_size=True,
+)
+
+# Circle parameters for 3-set Venn diagram (smaller radius to fit within canvas)
+r = 0.75
+n_points = 150
+theta = np.linspace(0, 2 * np.pi, n_points)
+
+# Circle centers in equilateral triangle arrangement (tighter to fit within margins)
+cx_a, cy_a = -0.4, 0.2  # Top left
+cx_b, cy_b = 0.4, 0.2  # Top right
+cx_c, cy_c = 0.0, -0.45  # Bottom center
+
+# Generate circle points for each set
+circle_a = [(cx_a + r * np.cos(t), cy_a + r * np.sin(t)) for t in theta]
+circle_b = [(cx_b + r * np.cos(t), cy_b + r * np.sin(t)) for t in theta]
+circle_c = [(cx_c + r * np.cos(t), cy_c + r * np.sin(t)) for t in theta]
+
+# Add circles as series (legend shows set sizes)
+chart.add(f"{set_labels[0]} (n={set_sizes[0]})", circle_a)
+chart.add(f"{set_labels[1]} (n={set_sizes[1]})", circle_b)
+chart.add(f"{set_labels[2]} (n={set_sizes[2]})", circle_c)
+
+# Render to SVG
+svg_content = chart.render().decode("utf-8")
+
+# Coordinate transformation: scale data coordinates to SVG pixels
+scale = 3600 * 0.35  # Scale factor for data to SVG conversion
+center_x = 3600 / 2
+center_y = 3600 / 2
+
+# Region count labels (positioned inside each region)
+count_style = 'font-size="52px" font-weight="bold" fill="#222" text-anchor="middle" dominant-baseline="middle"'
+name_style = 'font-size="40px" font-weight="bold" fill="#333" text-anchor="middle" dominant-baseline="middle"'
+
+labels = [
+    # Region counts - adjusted for new circle positions
+    (center_x + (cx_a - 0.35) * scale, center_y - (cy_a + 0.25) * scale, str(only_a), count_style),
+    (center_x + (cx_b + 0.35) * scale, center_y - (cy_b + 0.25) * scale, str(only_b), count_style),
+    (center_x + cx_c * scale, center_y - (cy_c - 0.4) * scale, str(only_c), count_style),
+    (center_x, center_y - (cy_a + 0.35) * scale, str(only_ab), count_style),
+    (
+        center_x + ((cx_a + cx_c) / 2 - 0.2) * scale,
+        center_y - ((cy_a + cy_c) / 2 - 0.08) * scale,
+        str(only_ac),
+        count_style,
+    ),
+    (
+        center_x + ((cx_b + cx_c) / 2 + 0.2) * scale,
+        center_y - ((cy_b + cy_c) / 2 - 0.08) * scale,
+        str(only_bc),
+        count_style,
+    ),
+    (center_x, center_y - ((cy_a + cy_c) / 2) * scale, str(abc_overlap), count_style),
+    # Set name labels (positioned further INSIDE circles to prevent cut-off)
+    (center_x + cx_a * scale, center_y - (cy_a + 0.35) * scale, set_labels[0], name_style),
+    (center_x + cx_b * scale, center_y - (cy_b + 0.35) * scale, set_labels[1], name_style),
+    (center_x + cx_c * scale, center_y - (cy_c - 0.45) * scale, set_labels[2], name_style),
+]
+
+# Build and insert SVG text elements
+text_elements = "\n".join(f'<text x="{x:.0f}" y="{y:.0f}" {s}>{v}</text>' for x, y, v, s in labels)
+svg_content = svg_content.replace("</svg>", f"{text_elements}\n</svg>")
+
+# Save SVG (with labels)
+with open("plot.svg", "w", encoding="utf-8") as f:
+    f.write(svg_content)
+
+# Render to PNG using cairosvg (includes the manually added labels)
+cairosvg.svg2png(bytestring=svg_content.encode("utf-8"), write_to="plot.png")
+
+# Create interactive HTML version
+html_content = f"""<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <title>venn-basic - pygal - pyplots.ai</title>
+    <style>
+        body {{ margin: 0; padding: 20px; background: #f5f5f5; display: flex; justify-content: center; }}
+        svg {{ max-width: 100%; height: auto; }}
+    </style>
+</head>
+<body>
+    {svg_content}
+</body>
+</html>"""
+
+with open("plot.html", "w", encoding="utf-8") as f:
+    f.write(html_content)
diff --git a/plots/venn-basic/metadata/pygal.yaml b/plots/venn-basic/metadata/pygal.yaml
@@ -0,0 +1,29 @@
+library: pygal
+specification_id: venn-basic
+created: '2025-12-29T23:29:36Z'
+updated: '2025-12-29T23:48:14Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20584842103
+issue: 0
+python_version: 3.13.11
+library_version: 3.1.0
+preview_url: https://storage.googleapis.com/pyplots-images/plots/venn-basic/pygal/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/venn-basic/pygal/plot_thumb.png
+preview_html: https://storage.googleapis.com/pyplots-images/plots/venn-basic/pygal/plot.html
+quality_score: 78
+review:
+  strengths:
+  - Creative workaround using XY chart to draw circles since pygal lacks native Venn
+    support
+  - All 7 regions are properly labeled with correct counts
+  - Good color palette with transparency for overlapping regions
+  - Legend includes set totals which adds useful information
+  - Mathematically correct calculation of exclusive regions
+  - HTML output provided for interactivity
+  weaknesses:
+  - Rendering artifact visible as a thin vertical line on the right edge of the yellow
+    circle
+  - Implementation relies heavily on manual SVG text injection rather than pygal native
+    features
+  - Circles are not proportional to set sizes as mentioned in spec
+  - Bottom margin has excess whitespace; circles could be more centered
