illustration-extract-template

Imported from okou-ai/vm0-skills (extract-template/illustration/SKILL.md). Install upstream with npx skills add okou-ai/vm0-skills --skill illustration. Copyright stays with the author.

Extract a reusable style from a reference picture

Input: images of one style, or a brief when no reference exists. Output: the user's own style, saved once they have seen what it makes and said it is right.

No extraction is complete. Measurement settles canvas, ground, palette, stroke, coverage and placement. Medium, drawing and subject convention are read by eye and are partly wrong on the first pass. The user closes that gap by looking at pictures, so the path is: extract, show, revise, save.

Choose among your own candidates without asking — the gate ranks them. Stop before saving, always: never save a prompt the user has not seen pictures from.

Run every command below from extract-template/illustration/.

Before anything — a style, or this one picture?

A style makes new pictures: another subject, another scene, the same look. A picture is one arrangement the user wants back.

For one picture, write the prompt that recreates it and stop. Continue here only for a style.

Prerequisites

python3 -c "import pymupdf"     # else: pip install pymupdf

Steps

1. Collect the references

Download every [Web file] with okou web download-file.

The scripts read PNG, JPEG, TIFF, BMP, GIF, JPEG 2000 and Netpbm. They do not read WebP, AVIF, HEIC or ICO — the formats a phone or a web page hands over. Convert those before step 2, and keep the original:

ffmpeg -loglevel error -y -i <ref.webp> <ref.png>

Ask for what is missing, and nothing else:

• intended use — blog cover, product card, marketing poster, in-app spot illustration. It decides the canvas and the frame.
• a slug — kebab-case, the name the saved style is called by. Propose two or three from the reference if the user has none.

With no reference at all, write the frame from the brief and go to step 4. Steps 2 and 3 need pixels.

Three or more references separate a locked axis from a dial. With one, ask for more; if none arrive, record in design-system.md which axes stay unsettled and give them no range.

Ask for files at least 400px on the short side. Below that the palette fills with anti-alias blends and the stroke is one pixel wide, so colour and line describe the downscaling.

2. Measure

python3 scripts/measure_style.py <ref> [<ref> ...] --json style.json

Take these numbers over your own reading of the image. The verdict column decides where each axis goes:

The shared-colour line is the locked palette; every other colour is a palette dial.

3. Read what the numbers cannot reach

Keep two records apart:

• content — subject, action, props, setting, placement;
• style — how it is drawn, carrying no content noun.

Then delete every subject, object, place and name from the style record. What remains must still describe a way of drawing; move anything else back to content.

Write every style line as a drawing instruction that names the near miss it excludes. A line that only names the family collapses into the nearest common style — flat vector, cel anime, stock watercolour — whatever the reference actually was.

State the style under these heads, from the references only:

Then name the dials — what changes from piece to piece. Three to seven. These carry across styles:

4. Write the style prompt

Write the prompt first; it is the deliverable. Its first third carries the locked frame, then the subject, then the dials, then what must not appear.

Keep these behind it, and write them into the package at step 8:

• Locked frame — one line per axis, measured values included. State the contour width in pixels at the canvas the package delivers, not only as a percentage: the references are rarely that size. State how much of the sheet the art covers and whether the ground stays unpainted — without it the model floods the sheet and the paper stops being a colour.
• Dials — one line per dial named in step 3, with the values the references used and what else the dial may take.
• Not in the frame — techniques absent from every reference.
• Prompt template — one prompt with a placeholder per dial, opening on the locked frame.
• References — one line per file naming the dial values it demonstrates.

design-system.md carries the measurement table per reference, the verdict table, and the axes a single reference could not settle.

Write the prompt template so the locked frame occupies its first third.

5. Generate, measure, choose

npx --yes --package="${CLI_PKG_URL}" okou generate image --provider built-in \
  --raw-prompt "<the style prompt, dials filled in>"
python3 scripts/check_piece.py --refs <ref> [<ref> ...] --piece <generated> [...]

Generate three at a time — that is the ceiling on generations in flight — each on a subject the references do not carry, and each moving a different dial: another scene metaphor, another complexity level, another palette value. Three pieces of the same subject show the style sitting still, not flexing.

Keep the ones with the fewest axes outside range. Use the built-in image model; if it fails for this style, say so and ask how to proceed rather than routing to another provider.

Read the failing axes: they name what the prompt did not hold. Correct the prompt and generate again.

Some axes never come back from the prompt. When two rounds do not move one, stop rewriting and fix it after the fact where that is possible. Scale and placement on a plain ground is the common one:

python3 scripts/compose.py --ref <reference> --piece <generated> --out <placed>

It scales the drawing's ink box to the fractions the reference measures and places it at the reference's margins, touching nothing inside the drawing.

Show only pieces the gate passes. When an axis will not come back, keep the best set and carry that one sentence into step 6.

The check cannot see medium, line quality, shape language, subject conventions, motif or composition. Look at the kept piece for those before delivering.

6. Show the pictures and ask whether the style is right

Put in the reply:

• the pictures as markdown images, one line under each naming its subject and the dials it moved — "L1, sage palette, single character";
• one line saying these were generated from the style in their reference.

Then ask one question: does this style look right.

This is a yes or no, not a survey. Do not list the axes, do not ask what to fix, do not offer options. When something still departs from the reference after step 5 did what it could, say it in one plain sentence — the lines came out heavier than the reference, the palette runs warmer — and leave it there.

Show the prompt only if the user asks for it.

Stop. Save nothing yet.

7. Revise, then show again

The user speaks about the look — the lines are too heavy, it is too colourful, the faces are wrong. Turn each correction into one line of the locked frame that names the near miss it excludes, the same form as step 3. Nothing else in the prompt changes.

Regenerate the set with step 5 and show it again. One round of corrections at a time; do not bundle two rounds into one reply.

Repeat until the user says it is right.

8. Save it as the user's template

Only after the user says the style is right.

Build the package under the slug from step 1:

<slug>/
  SKILL.md                 frontmatter with the trigger phrases, the locked
                           frame, the dials, the prompt with its placeholders,
                           and two or three example briefs
  design-system.md         the measurement table per reference, the verdict
                           table, and the axes a single reference could not
                           settle
  ref-<subject>-<dial>.png the approved pictures

Leave the user's references out of the package; the primary one is published beside it as the source. With no reference at all, publish an approved picture as the source instead.

Generate one piece from the SKILL.md you just wrote rather than from the prompt in your notes, and check it still matches the approved pictures. Publish only after that.

npx --yes --package="${CLI_PKG_URL}" okou user-template publish \
  --title "<user-visible style name>" \
  --kind illustration \
  --source <the primary reference> \
  --package <slug>

--source takes PNG, JPEG, BMP or WebP. Convert anything else — AVIF, HEIC, GIF, TIFF, JPEG 2000, Netpbm — and pass the PNG:

ffmpeg -loglevel error -y -i <ref.heic> <ref.png>

Say the template exists only after the command succeeds; name the specific blocker if it fails.

Then report, in this order: what the style is called and that it is under Custom in the template picker, the link to the picture the user approved, and anything still open — a dial with one value, a complexity level never tested, an axis that departs from the reference.

Register it as a built-in selectable style only when the user asks: the resource goes to illustration-template/<slug>/ in okou-ai/vm0-skills, its entry to the Open Design registry in okou-ai/okou as vm0:image-style:<slug> with a selection description of 150 characters or less, and each pull request links the other.

Rules

• Reproduce the references. Do not correct a palette, a proportion or a stroke you would have drawn differently.
• Present in every reference is locked; present in one is a dial; with a single reference, neither — say so rather than guessing.
• A technique absent from every reference is part of the locked frame. A subject or content type absent from them is not a rule.
• Name observable technique, never an artist, studio, brand or product.
• Numbers in the package come from step 2, not from reading the image.
• Step 5 is mandatory. Show pictures you generated, never only a prompt.
• Choose among your own candidates yourself. Do not hand the user a menu of variations.
• Step 6 stops, and asks one yes-or-no question. Saving before the user has seen pictures and approved them is the one thing this skill must never do.
• A correction from the user is one more line in the locked frame, not a rewrite of the prompt.
• Rotate the cast and the scene across a series. A locked frame is not a locked mascot.
• Use the built-in image model. When it cannot hold a style, say so; do not route to another provider without asking.
• Nothing is published from an untested style. Generate one piece from the written SKILL.md first.
• The user's reference files are never part of the package. The primary one is the published source; the rest served steps 2 and 3 and stop there.

Troubleshooting