Pixel Art

pixel-art

A pocket-sized pixel-art studio. You hand it a short brief — "medieval harbor at dusk", "tavern interior with fireplace", "Whispers of the Flame title card in VT323" — and it returns a finished image (whenever any image generator is reachable) or a model-agnostic prompt brief you can paste into the generator of your choice. The style is locked in references/ so you do not have to re-describe palette, density, composition, lighting, or typography every time.

Repo-agnostic. This skill assumes no repository and writes nothing to disk. Every artifact — the generated image, the quantized PNG/SVG, the prompt brief, the title-card SVG — is returned to the caller, who decides what to do with it. (Ephemeral temp files used purely to hand a raster to the quantize script are fine; persisting to a repo path is not.)

When to use this skill

• "Create a pixel-art [scene / character / building / forest / title card] of …"
• "Make a hi-fi pixel-art harbor at dusk."
• "Generate a lo-fi pixel banner like the agent-skills banners."
• "Title card for 'Whispers of the Flame' in VT323."
• "I want this image in the same hi-density pixel style as before."
• "Make this image a pixel-art version of itself."
• "Give me that sprite as SVG." (single generated sprite → WS4 serialize)

If the user provides a reference screenshot and says "this style", treat it as stylistic intent (palette / density / mood). Do not copy the reference image; produce an original composition that hits the same craft markers (see references/anti-patterns.md).

When NOT to use this skill

• Composed / branded SVG-asset jobs — banners, icon sets, branded SVGs, multi-asset sets, anything needing exact rendered text, an exact layout/viewBox, brand tokens, or an editable vector source. This skill generates a single raster; it does not author composition. See the Phase 0 gate — it declines these honestly rather than substituting a raster.
• Vector illustration / icon design — use canvas-design or hand-author SVG. Pixel art is raster-first; vectors are a different craft.
• Logo or brand identity package — route to brand-workshop.
• Photo-realistic generation — wrong style; use a general image-gen model directly with a non-pixel-art prompt.
• Algorithmic / generative art with p5.js, particle systems, flow fields — use Anthropic's algorithmic-art skill.
• Charts, dashboards, data visualization — use the data viz skills.
• Rasterizing an existing photograph as pixel art — out of scope; consider an external "pixelate" filter instead.

Phase 0 — Deliverable-type gate (run FIRST)

Before anything else, decide whether this is a job the skill does. pixel-art is a single-subject generative skill: it produces a raster and may serialize one sprite as SVG. It does not author composed deliverables.

If the brief needs any of the following, it is a composition/authoring job and you must decline:

• exact rendered text (a banner/title with specific words laid out),
• an exact layout or viewBox,
• exact brand tokens / a brand spec,
• an editable / vector source as the deliverable,
• a multi-asset set (icon set, banner family, sprite sheet).

How to decline: state the mismatch plainly — "You asked for <deliverable>, which needs <exact text / layout / vector source / a set>. pixel-art generates a single raster (optionally one sprite as SVG); it does not author composed SVG assets, so I can't produce this honestly." Then stop. Do not down-convert the request to a raster, and do not name a substitute tool — routing is the caller's call.

Carve-outs (NOT a decline):

• Title card — the title-card.svg template is the one grandfathered authored-SVG path. A title-card request (even with exact title text) proceeds to the title-card SVG path in Phase 4. This is the single exception to "no exact rendered text."
• Single-sprite SVG — "give me that generated sprite as SVG" is a serialize of one generated raster (Phase 4 / WS4 quantize), not a composed asset. Proceed.

If the request passes the gate (a single scene / character / building / nature / title-card / sprite), continue.

Phase 1 — Style mode

Two modes. Default is hi-fi. Confirm only if the user's brief is ambiguous (e.g., "make a pixel-art banner" — banners are usually lo-fi here).

The selected mode controls which palette block loads from references/palette.md and which density profile loads from references/density.md. Composition rules and font catalog are shared.

Phase 2 — Subject detection

Map the user's brief to one of five subjects. Each subject has its own prompt template in templates/ and (when relevant) its own composition rules in references/composition.md.

If the brief mixes subjects ("character in a forest"), pick the dominant subject (here: scene, with the character as a foreground element). Note the secondary subject in the prompt's composition block.

Phase 3 — Compose the prompt

Read the following references once at the start of the task:

1. references/style-modes.md — confirms hi-fi vs lo-fi profile
2. references/palette.md — named palettes; pick one by mood
3. references/density.md — pixel density + dithering rules per mode
4. references/composition.md — layout, eye-line, light-source rules
5. references/lighting.md — time-of-day + mood + color-temp guidance
6. references/anti-patterns.md — craft-marker checklist + what to avoid
7. references/fonts.md — only if subject is title-card

Then load the subject template from templates/ and fill its prompt blocks. The universal block structure is the same across subjects:

[STYLE]      hi-density pixel art / lo-fi scanlined pixel art
[PALETTE]    <named palette> — <hex anchors>
[SUBJECT]    <one-line subject description>
[COMPOSITION] <foreground / midground / background, eye-line, focal point>
[LIGHTING]   <time of day, key/fill direction, mood>
[DENSITY]    <density anchor name, dithering policy>
[MOOD]       <2–4 adjectives>
[NEGATIVE]   <anti-patterns to forbid — see anti-patterns.md>

This block format is deliberately model-agnostic — it accepts structured natural-language prompts across any image generator. Optional per-model phrasing nudges live in references/model-routing.md.

Phase 4 — Generation routing (attempt-then-fallback)

Two paths. Do not silently fall through — name which path is running.

The routing question is "can I generate at all?", not "is a specific named MCP connected?" Host-native image generation often isn't introspectable from inside a skill, so detect by attempting, not by checking a vendor list.

Path A — Inline generation (preferred whenever reachable)

Attempt inline generation using any available image-generation capability — host-native OR an MCP tool. If you can produce an image in this runtime, do it. Pass the composed prompt (Phase 3) to the generator; apply optional per-model phrasing tweaks from references/model-routing.md if you happen to be on a generator listed there (the list is nudges, not a gate).

After generation, run the deterministic quantize pass (next section), then return the quantized artifact + the finalized prompt to the caller. Do not write either to a repo path — return them as values (image bytes/handle + the prompt text). The caller decides where they go.

Density note (advisory, not a gate): generators differ in how fine a pixel grain they reach from prompting alone. If an output misses the density anchor you named, regenerate with adjusted blocks, or — if you have another generator available — try it. This is advice, not a hard route-off rule; the quantize pass below also normalizes grain.

Quantize post-process (deterministic)

Raw diffusion output is pseudo pixel art — tens of thousands of unique colors, no true grid. Run scripts/quantize.py (in this skill's directory; needs Pillow — pip install -r scripts/requirements.txt) to make it real grid-aligned pixel art:

python3 scripts/quantize.py <in.png> --format <png|svg> [--grid N] [--palette N] [--ramp <hexlist>] [--scale N]

Pipeline: nearest-neighbor downscale to the target grid → median-cut palette quantize (deterministic; honors a supplied fixed ramp) → optional ordered dither + orphan-pixel cleanup → nearest-neighbor upscale ×N for display. Defaults: grid 128–256px, palette 24–48 colors, dither off, median-cut palette. Output switch emits PNG or SVG (SVG = one <rect> per run-length-merged cell — single sprite only, not a banner/composition path). Return the requested format to the caller.

If Pillow is unavailable and can't be installed, say so and return the un-quantized raster with a noted caveat — don't silently skip the step.

Path B — Prompt-brief (only when generation is genuinely impossible)

If you cannot generate an image by any means in this runtime (no host-native capability and no image-gen MCP), OR the user explicitly asks for a copy-pasteable prompt, emit a prompt brief following templates/prompt-brief-fallback.md. Return the brief to the caller (do not write it to disk). The brief includes:

1. The model-agnostic prompt (universal block format from Phase 3).
2. Optional per-model variants for common generators (nudges only).
3. Negative prompt block (anti-patterns).
4. A note that the prompt is model-agnostic.

Do not call Path B "fallback" in user-facing output — call it "prompt brief" or "copy-pasteable prompt." It is a first-class deliverable.

Title-card SVG path (additive)

If subject is title-card, always also produce a code-based SVG from templates/title-card.svg. This SVG uses VT323 by default (per Kiang) and accepts the font, palette, and title text as template tokens. It is portable (renders in browsers, exports to PNG), and gives the user a path that does not depend on any image generator at all. Return the filled SVG to the caller (do not write it to disk). This is the one authored-SVG path the skill retains (see the Phase 0 carve-out).

When both Path A and the SVG path run, surface both: "Here's the generated + quantized image, and a portable SVG title card — pick whichever fits your use case."

IP guardrail (non-negotiable)

Mirror algorithmic-art's standard:

• Never reference any specific named artist in any prompt — living or deceased (no "in the style of [artist]", no "[artist]-style"). Deceased artists' work is typically still under copyright; the guardrail applies regardless of life status. Rewrite the prompt to encode craft markers instead.
• Never copy a specific copyrighted work. If the user supplies a reference screenshot, treat it as stylistic intent only and produce an original composition.
• Any reference examples you return should be original generations, not derivatives of third-party reference imagery.

If a user prompt names any specific artist (living or deceased), rewrite it before generating: replace the artist name with the craft markers that artist's style would have evoked (high-density, painterly mid-tones, warm palette, etc.). Note the rewrite in the user-facing output.

Verification

Deliverable-type check (run FIRST)

Before the craft check, confirm the output's kind matches the request: a single raster (or one-sprite SVG / title-card SVG) for a generative brief; an honest decline for a composition/authoring brief (Phase 0). If you generated a raster for something that should have been declined, that is the failure this skill exists to prevent — stop and decline instead.

Craft-marker checklist

Then run the checklist in references/anti-patterns.md. Hi-fi mode requires at least 5 of 6 craft markers present (marker 6 added in v3.10.1; this section is the SKILL.md summary — references/anti-patterns.md is authoritative on the full checklist and regenerate-recipes):

1. Deliberate hue shifts in shadow / light ramps (not pure lightness change).
2. Cluster studies — no orphan single pixels.
3. Banding avoidance — no long stripes of uniform color without breakup.
4. Painterly mid-tones via ordered dithering where appropriate.
5. Clean edges — silhouettes legible, no anti-aliasing fringe.
6. Pixel scale matches the density anchor — output's pixel scale lands in the band named in [DENSITY]. Markers 1–5 check how pixels behave; marker 6 checks whether they are the right size.

Lo-fi mode is more permissive — the scanlined warm-paper background is the main anchor; the craft markers above are nice-to-have.

If the generation fails the checklist, surface the gap to the user and offer to regenerate with adjusted prompt blocks (usually a density bump or a different palette).

File map

skills/pixel-art/
├── SKILL.md                 (this file)
├── README.md                (user-facing docs)
├── references/
│   ├── style-modes.md       (hi-fi vs lo-fi profiles)
│   ├── palette.md           (named palettes by mood)
│   ├── density.md           (pixel density + dithering rules)
│   ├── composition.md       (layout, eye-line, light source)
│   ├── lighting.md          (time-of-day, mood, color-temp)
│   ├── fonts.md             (VT323 default + 4 alternates)
│   ├── anti-patterns.md     (craft-marker checklist + forbid list)
│   └── model-routing.md     (optional per-model phrasing nudges)
├── scripts/
│   ├── quantize.py          (deterministic median-cut quantize → PNG/SVG)
│   ├── test_quantize.py     (stdlib assert-based invariants)
│   └── requirements.txt     (Pillow)
└── templates/
    ├── scene-prompt.md
    ├── character-prompt.md
    ├── building-prompt.md
    ├── nature-prompt.md
    ├── title-card-prompt.md
    ├── title-card.svg       (SVG template with VT323)
    └── prompt-brief-fallback.md

Cross-skill integration

When to use this skill

(Trigger phrases above. Repeated here for the cross-tool SKILL.md standard — Codex and other parsers look for this header.)

• "create pixel art [of X]"
• "pixel-art [scene / character / building / nature / title card]"
• "hi-fi pixel art" / "lo-fi pixel art"
• "VT323 title card" / "pixel-font title"
• "make this a pixel-art version"
• "generate a pixel-art [subject]"
• "give me that sprite as SVG" (single generated sprite)
• "I want this style" + hi-density pixel-art reference

Tags: pixel-art, image-generation, design-system, hi-density, lo-fi, title-card, VT323, model-agnostic, quantize, repo-agnostic.

License

MIT. See repo root LICENSE.