feat(letsplot): implement waveform-audio

[github-actions]

Implementation: waveform-audio - python/letsplot

Implements the python/letsplot version of waveform-audio.

File: plots/waveform-audio/implementations/python/letsplot.py

Parent Issue: #4563

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

Light render (plot-light.png): Warm off-white #FAF8F1 background. Title "waveform-audio · python · letsplot · anyplot.ai" in dark ink at size 16, clearly readable. Subtitle in INK_SOFT gray. X-axis "Time (seconds)" and Y-axis "Amplitude" labels at size 12, tick labels at size 10. Section annotations (Attack, Sustain, Dip, Sustain, Release) in dark italic text above the waveform at y=1.07. Dense vertical segment bars rendered with Imprint sequential gradient from #009E73 (green, low amplitude range) to #4467A3 (blue, high amplitude range). Waveform clearly shows ASR envelope: tall sustain sections (±1.0), reduced dip section (±0.5), gradual release taper. Dotted vertical boundary lines at section transitions and dashed zero reference line. Colorbar legend "Amplitude Range" on right. All text is readable against the warm off-white background.

Dark render (plot-dark.png): Warm near-black #1A1A17 background — correct. Title in #F0EFE8 (INK dark token), clearly readable. Subtitle in #B8B7B0 (INK_SOFT dark). Axis labels, tick labels, and section annotations all rendered in light-colored tokens — no dark-on-dark failures. Waveform segment colors identical to light render: same #009E73→#4467A3 Imprint sequential gradient. Dashed zero line and dotted section boundary lines visible in theme-adaptive INK_MUTED. Colorbar legend readable with light text. All text is readable against the near-black background.

Both paragraphs confirmed. A review that only describes one render is invalid.

Score: 90/100

Category	Score	Max
Visual Quality	30	30
Design Excellence	13	20
Spec Compliance	15	15
Data Quality	15	15
Code Quality	10	10
Library Mastery	7	10
Total	90	100

Visual Quality (30/30)

• VQ-01: Text Legibility (8/8) — All font sizes explicitly set (title=16, axis=12, tick=10, annotations=4mm). Readable in both themes, well-proportioned.
• VQ-02: No Overlap (6/6) — Section annotations at y=1.07 clear of waveform. No overlapping text elements.
• VQ-03: Element Visibility (6/6) — 800-bin min/max envelope with alpha=0.85, size=1.5 — ideal density for waveform rendering.
• VQ-04: Color Accessibility (2/2) — Imprint sequential gradient is CVD-safe. Reference lines use neutral INK_MUTED.
• VQ-05: Layout & Canvas (4/4) — 3200×1800 canvas (gate passed). Legend well-placed on right. Generous margins via plot_margin=[40,20,20,20].
• VQ-06: Axis Labels & Title (2/2) — X: "Time (seconds)", Y: "Amplitude" — descriptive with units.
• VQ-07: Palette Compliance (2/2) — scale_color_gradient(low='#009E73', high='#4467A3') = correct imprint_seq. Backgrounds #FAF8F1/#1A1A17. Full theme-adaptive chrome in both renders.

Design Excellence (13/20)

• DE-01: Aesthetic Sophistication (5/8) — Thoughtful multi-layer design: color encodes amplitude range, section labels annotate phases, dotted boundary lines add structural context. Above defaults but not publication-ready FiveThirtyEight level.
• DE-02: Visual Refinement (4/6) — X-grid removed, Y-grid with rgba(26,26,23,0.15) opacity, theme_minimal() + full custom chrome, clean elevated legend background.
• DE-03: Data Storytelling (4/6) — ASR phase labels with boundary lines create a clear narrative of the musical envelope. Color encoding reinforces amplitude intensity story. Zero baseline provides audio engineering reference.

Spec Compliance (15/15)

• SC-01: Plot Type (5/5) — Correct audio waveform visualization with envelope-based rendering.
• SC-02: Required Features (4/4) — Zero reference line ✓, time x-axis with seconds ✓, amplitude ±1.0 ✓, min/max envelope binning ✓, synthetic data ✓.
• SC-03: Data Mapping (3/3) — X=time in seconds, Y=amplitude ±1.0. Full 1.5s duration visible.
• SC-04: Title & Legend (3/3) — Title "waveform-audio · python · letsplot · anyplot.ai" correct format. Colorbar legend "Amplitude Range" appropriate.

Data Quality (15/15)

• DQ-01: Feature Coverage (6/6) — Attack ramp, sustain, amplitude dip, second sustain, release taper — all envelope phases visible and distinct.
• DQ-02: Realistic Context (5/5) — 220 Hz musical note with harmonics and ASR envelope — realistic audio engineering scenario.
• DQ-03: Appropriate Scale (4/4) — 22050 Hz sample rate, normalized ±1.0, 1.5s duration — all domain-appropriate.

Code Quality (10/10)

• CQ-01: KISS Structure (3/3) — Flat linear flow: imports → tokens → data → plot → save. No functions or classes.
• CQ-02: Reproducibility (2/2) — np.random.seed(42) set.
• CQ-03: Clean Imports (2/2) — os, numpy, pandas, lets_plot, ggsave — all used.
• CQ-04: Code Elegance (2/2) — Clean, appropriate complexity, no fake UI elements.
• CQ-05: Output & API (1/1) — Saves plot-{THEME}.png and plot-{THEME}.html correctly.

Library Mastery (7/10)

• LM-01: Idiomatic Usage (4/5) — Proper ggplot grammar, scale_color_gradient, theme() layering on top of theme_minimal(), layer_tooltips() — idiomatic lets-plot.
• LM-02: Distinctive Features (3/5) — layer_tooltips() with .format() configuration is lets-plot-distinctive. Native HTML export used. Missed opportunity: geom_ribbon() would be the more idiomatic lets-plot "filled area" geom for waveform rendering, better matching the spec's "filled area mirrored above and below zero" description.

Score Caps Applied

• None applied — DE-01=5 (>2) and DE-02=4 (>2), no "correct but boring" cap triggered.

Strengths

• DAW-style vertical segment rendering with Imprint sequential colormap (#009E73→#4467A3) adds meaningful amplitude-range color encoding beyond a basic waveform
• ASR phase annotations (Attack/Sustain/Dip/Release) with dotted boundary lines create clear data storytelling — viewer immediately understands envelope dynamics
• Correct min/max envelope binning (22050 samples → 800 bins) prevents aliasing at display resolution, matching spec guidance
• Perfect theme-adaptive chrome in both renders: #FAF8F1 light and #1A1A17 dark with all text tokens switched correctly
• Clean KISS code with np.random.seed(42), all sizes explicitly set, both PNG + HTML output files saved

Weaknesses

• Section annotation labels (Attack/Sustain/Dip/Release) all share the same thin italic style with no visual weight hierarchy — bolder or larger labels for primary phase transitions would add polish
• geom_ribbon(ymin='ymin', ymax='ymax') would be the more idiomatic lets-plot approach for the spec's "filled area mirrored above and below zero" rendering; geom_segment achieves the same visual but misses the higher-level API

Issues Found

1. DE-01 MODERATE: Design is above defaults but not publication-ready — section labels lack typographic hierarchy
   • Fix: Consider increasing annotation text size slightly (~5mm) and differentiating the primary phase labels visually
2. LM-02 PARTIAL: Uses layer_tooltips() but misses geom_ribbon which is the idiomatic lets-plot fill geom for waveform rendering
   • Fix: Could replace geom_segment with geom_ribbon(aes(ymin='ymin', ymax='ymax', fill='intensity')) for more native lets-plot idiom

AI Feedback for Next Attempt

Implementation is strong and scores 90/100 — approved as-is. If a repair were needed: use geom_ribbon() instead of geom_segment() for the filled-area waveform (more idiomatic lets-plot), and add slight visual hierarchy to section annotations (e.g., size=5 instead of 4). No functional or palette issues.

Verdict: APPROVED