Imported from oil-oil/oil-icon (SKILL.md). Install upstream with npx skills add oil-oil/oil-icon. Copyright stays with the author.

oil-icon

Generate a set of icons that share one visual style, output as transparent PNGs.

Image generation runs on a flat grey backdrop as a 4×4 sheet — 16 icons in one generation, so the set is stylistically consistent by construction — then each cell is sliced out and background-removed.

Claude owns the design decisions (which style, which palette, which metaphors, whether to match a brand); image generation and slicing are mechanical steps.

When to use / not

Use for: an icon pack, a product or brand icon set, spot / feature / marketing / empty-state / category icons, or icons matching a specific style or a project's design tokens.

Not for: a single one-off icon (draw an SVG), or dense functional UI glyphs at 16–24px (use a vector icon library such as lucide — raster icons are not crisp at tiny sizes). Generated icons are best at larger "spot" sizes.

Workflow

1. Choose the style. Either pick a built-in from styles/ (table below), or match the user's brand by reading their project's design tokens / assets and deriving a custom style-spec — see reference/style-adaptation.md. Freeze the result as a style-spec with the same fields as the built-in JSONs; the frozen spec is what keeps every future batch identical.
2. List the icons. Write each concept as name — short concrete metaphor (e.g. settlement — a wallet with a coin). One clear idea per icon; keep the detail level consistent across the set. Batch into sheets of 16, or 9 when you want maximum slicing stability. If the user asks for an exact count below 16, still use a 4x4 / 16-cell sheet: place the requested icons first in row-major order, then explicitly ask the remaining cells to stay empty grey background.
3. Compose the prompt. style.preamble + the style's construction fields (as short guidance) + palette-lock line + numbered metaphors + the fixed composition text — see reference/prompt-template.md and reference/construction.md.
4. Generate the sheet(s). Choose an image provider by capability, in order (see reference/image-providers.md) — never assume Codex is present:
   1. Built-in / host imagegen first — if the running agent already has a callable image-generation tool, including Codex's built-in image_gen tool or the imagegen skill, call it directly. Do not delegate to external Codex CLI just to reach imagegen from another process.
   2. Codex CLI fallback — only if this agent has no callable image-generation tool, and Codex is available (~/.claude/skills/codex/scripts/ask_codex.sh or codex on PATH), delegate generation to it.
   3. External API fallback — only if neither of the above exists, ask the user which image API + key to use; for OpenAI Images, scripts/gen_image.py --prompt "…" --out raw/<style>.png is ready. Save or copy each generated sheet to raw/<style>.png on flat grey #808080. Built-in imagegen may save under $CODEX_HOME/generated_images/...; after generation, move or copy the selected PNG into the oil-icon raw/ folder. One sheet = one generation = one consistent style; a provider only has to turn the prompt into a grey-background PNG.
5. Slice. Run scripts/setup.sh once, then: .venv/bin/python3 scripts/slice_icons.py <raw>.png <outdir> --mode <cutout> [--thresh N] [--grid 4] [--count N] using the style's cutout mode (floodfill for flat/hard-edge, rembg for soft / 3D / glossy / photo).
6. QA (mandatory). Composite the sliced PNGs onto a contrasting colour (e.g. magenta) and check every icon for (a) a fragment bled in from a neighbouring cell, (b) leftover grey, and (c) consistency against the style's construction — uniform stroke, one radius, matched detail level, shared parts, motif present, single perspective, and no accent out-weighting the defining element (in line styles the accent must be lighter and smaller than the stroke). Re-slice or regenerate any that fail — never ship an icon carrying part of the one above it.
7. Deliver the transparent PNGs, organized and named.

Built-in styles

Each styles/<name>.json holds the preamble, locked palette, cutout mode, threshold, construction system, and what it fits.

Key rules (see reference/design-rules.md)

• Lock the palette as hex in the spec — colourful styles drift run-to-run otherwise.
• Never make black filled icons — near-black / black may be used as a thin outline or line stroke, but never as the dominant filled mass of an icon set. If the brand foreground is black, map it to strokes only; for filled or duotone styles, choose a mid-light brand colour for the main shape and keep dark colours small.
• Start from the real product context — when a user gives a live site, screenshot, mascot, logo, or brand asset, derive the icon concepts and construction from that source first. Do not jump straight into generic style families such as isometric, duotone, 3D, or colorblock; those are finishes applied after the product motif, real navigation, and real feature names are locked.
• Slicing drops neighbour bleed — the slicer keeps only the centred icon per cell.
• Cutout by edge type — flat/hard-edge → floodfill; soft / 3D / glossy / photo → rembg.
• Design sophistication comes from a construction system + a brand motif, not from tinting a generic set — each style's construction object encodes the grid, stroke, radius, detail budget, shared parts, and motif (see reference/construction.md). A rigorous system ultimately wants vector; raster is for direction and spot icons.