文章は簡単な部分：AIが書いた記事に挿絵を入れるパイプライン

┌─ 1. WRITE ────────────────────────────────────────────────────┐
   topic ──▶ LLM ──▶ draft.md  (h2 sections, front-matter)
└───────────────────────────────┬───────────────────────────────┘
┌─ 2. BRIEF ────────────────────┴───────────────────────────────┐
   draft.md ──▶ LLM ──▶ { hero: {...}, sections: [ {...} ] }
                     one JSON object: per slot, a kind +
                     either a camera brief or a data/diagram spec
└──────────┬──────────────────────────────────┬─────────────────┘
           │ kind = "photo"                │ kind = "chart" | "diagram"
           ▼                               ▼
┌─ 3. SEARCH ───────────────┐   ┌─ 4. DRAW (optional) ─────────┐
   GET /search/photos          LLM ──▶ mermaid | plotting code
   ← credited photo +           ──▶ sandbox ──▶ .svg / .png
     w/h, blur_hash, alt,       (deterministic render, no
     licence, source URL         invented numbers)
└──────────┬────────────────┘   └──────────────┬───────────────┘
           └───────────────┬──────────────────┘
┌─ 5. ASSEMBLE ─────────────┴───────────────────────────────────┐
   <img> with width/height + fetchpriority | loading
   alt written for a human · visible credit · ImageObject JSON-LD
   photo_id stored so no two pages share a hero
└───────────────────────────────────────────────────────────────┘

# system prompt — run once per finished draft
You are the art director of a technical publication. Read the article and
return the visual plan: one entry for the hero, one per H2 section.

For each entry choose exactly one kind:
  "photo"    a real scene: someone doing something somewhere, a place,
              an object, a gesture. The default for heroes.
  "chart"    the section states numbers that are IN the article. Never
              invent values: copy them into data, verbatim.
  "diagram"  the section describes a structure, a flow or a sequence.
  "none"     the section is short, or already carries a code block.

Rules for "photo" entries — the field is query:
カメラブリーフを書いてください。カメラが撮影できるであろうシーンを、
   英語で12語から25語で、そのセクションの雰囲気に合わせて記述します。
   フレームの中に写っているものを名指しし、トピックそのものは書かない
   こと。文字、ロゴ、ブランド、有名人は不可。目に見えない比喩も不可。
   (完全なルール、例と失敗例付き：
   pexafy.com/blog/illustrate-blog-articles-at-scale/)

Do NOT write the alt text of a photo entry: the picture you get back is the
closest match to the brief, not the scene you described, so its alt has to be
written from the chosen photo. Chart and diagram entries DO carry an alt —
there you control exactly what is rendered.

Return JSON only:
{
  "hero": { "kind": "photo", "query": "…", "orientation": "landscape" },
  "sections": [
    { "h2": "…", "kind": "photo",   "query": "…" },
    { "h2": "…", "kind": "chart",   "title": "…", "unit": "ms",
      "data": [ {"label": "…", "value": 0} ], "alt": "…" },
    { "h2": "…", "kind": "diagram", "spec": "flowchart LR; …", "alt": "…" }
  ]
}

{
  "photo_id":  "019e1c7f-0063-759e-b498-33ce1714e6c9",   // store it: no repeats
  "urls": { "small": "…?w=400", "regular": "…?w=1080",
             "large": "…?w=1920" },
  "width": 3000, "height": 1688,          // → no layout shift
  "blur_hash": "LJ8gjv9rVq-6OFxanNNFI7xco$Na",   // → real placeholder
  "alt_description": "Person types on keyboard in front of dual monitors…",
  "photographer_full_name": "Jakub Żerdzicki",   // → ImageObject.creator
  "source": "Unsplash", "license_type": "free",
  "source_image_url": "https://unsplash.com/photos/…",
  "attribution": { "html": "<span…>Photo by …</span>",
                    "plain": "Photo by Jakub Żerdzicki on Unsplash (…)" }
}

# the "spec" field of a diagram entry, written to build/graph.mmd
cat build/graph.mmd
flowchart LR
  install["install deps · 480s"] --> compile["compile · 1080s"]
  compile --> test["test suite · 720s"]
  compile --> upload["upload artifacts · 120s"]

npx -y @mermaid-js/mermaid-cli -i build/graph.mmd -o static/img/graph.svg
# → an SVG you can review in the PR, not a picture you have to trust

import re, matplotlib
matplotlib.use("Agg")                # headless: no display in CI
import matplotlib.pyplot as plt

def assert_in_draft(value, draft: str) -> None:
    """A plotted number must appear in the article AS A NUMBER."""
    # Substring matching is the trap here: "120" is inside "1200", and
    # inside "?w=1200" — a naive `str(v) in draft` passes on anything.
    # Match on word boundaries, and accept 1 234 / 1,234 / 1234.
    body = re.sub(r"(?<=\d)[  ,](?=\d{3}\b)", "", draft)   # strip separators
    if not re.search(rf"(?<![\d.]){re.escape(str(value))}(?![\d.])", body):
        raise ValueError(f"{value} is not stated in the article — refusing to plot")

def render_chart(entry: dict, draft: str, out: str) -> str:
    labels = [d["label"] for d in entry["data"]]
    values = [d["value"] for d in entry["data"]]
    for v in values:
        assert_in_draft(v, draft)       # hallucinated value → no chart

    fig, ax = plt.subplots(figsize=(8, 4.5), dpi=160)
    ax.barh(labels, values)
    ax.set_xlabel(entry["unit"])
    ax.set_title(entry["title"])
    fig.tight_layout()
    fig.savefig(out)                    # deterministic, reviewable artefact
    return out

<!-- The bytes come from another origin: pay the handshake early -->
<link rel="preconnect" href="https://images.unsplash.com" crossorigin>

<!-- LCP element: never lazy, always high priority -->
<figure>
  <img src="{urls.regular}"
       width="{width}" height="{height}"        <!-- kills layout shift -->
       alt="{alt}"                                <!-- written AFTER the pick -->
       fetchpriority="high" decoding="async"
       style="background:{color_hex}">   <!-- dominant colour, 1 field -->
  <figcaption>{attribution.html}</figcaption>
</figure>

<!-- Section images, below the fold: the opposite settings -->
<img src="{urls.regular}" width="{width}" height="{height}"
     alt="{alt}" loading="lazy" decoding="async">

<script type="application/ld+json">
{
  "@context": "https://schema.org/",
  "@type": "ImageObject",
  "contentUrl": "{urls.large}",                 // required
  "creator": { "@type": "Person",
                "name": "{photographer_full_name}" },
  "creditText": "{photographer_full_name} on {source}",
  "license": "{LICENSE_URL[source]}",           // the library's own page
  "acquireLicensePage": "{source_image_url}"     // the photo's page
}
</script>

# LICENSE_URL maps the `source` field to the licence that actually governs
# the photo — unsplash.com/license, pexels.com/license, pixabay.com/…

on: { pull_request: { paths: ["content/**.md"] } }

jobs:
  illustrate:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: pip install -r requirements.txt
      - run: python plan_to_pr.py $(git diff --name-only origin/main -- 'content/*.md')
        env:
          PEXAFY_API_KEY: ${{ secrets.PEXAFY_API_KEY }}
          ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}
      - uses: peter-evans/create-pull-request@v6   # images land in the PR
        with: { commit-message: "chore(content): illustrate" }

import frontmatter
from photo_search import search   # GET /search/photos を1回呼ぶ。`used` にあるIDはスキップ

def find_photo(entry: dict, used: set) -> dict | None:
    """Search; if the brief was too specific, widen it once, then give up."""
    orientation = entry.get("orientation", "landscape")
    for query in (entry["query"], widen(entry["query"])):
        photo = search(query, orientation, used)
        if photo:
            used.add(photo["photo_id"])   # claim it: no repeats site-wide
            return photo
    return None                        # caller decides: skip the slot, or fail

def widen(query: str) -> str:
    """Drop the last clause — usually the over-specific one."""
    return query.rsplit(" in ", 1)[0] if " in " in query else query

def illustrate(path: str, plan: dict, used: set) -> None:
    post = frontmatter.load(path)
    hero = find_photo(plan["hero"], used)
    if hero is None:                    # no hero is better than a bad one
        raise SystemExit(f"{path}: no photo above threshold — rewrite the brief")

    post["hero"] = {                    # everything the template needs
        "src": hero["urls"]["regular"], "w": hero["width"], "h": hero["height"],
        # The alt describes the photo we GOT, never the scene we asked for.
        "alt": alt_for(hero, section=post.get("title", "")),
        "bg": hero["color_hex"], "credit": hero["attribution"]["html"],
        "creator": hero["photographer_full_name"], "id": hero["photo_id"],
        "source": hero["source"],
        "source_url": hero["source_image_url"],   # → acquireLicensePage
    }
    open(path, "w").write(frontmatter.dumps(post))

def alt_for(photo: dict, section: str) -> str:
    """alt_description as the base, trimmed to ~125 chars for screen readers.
    Send it back through the model with the paragraph if you want better."""
    base = photo.get("alt_description") or photo.get("description", "")
    return base[:125].rstrip(" ,;")

from playwright.sync_api import sync_playwright

with sync_playwright() as p:
    browser = p.chromium.launch()
    page = browser.new_page(viewport={"width": 1440, "height": 900},
                            device_scale_factor=2)   # retina-crisp
    page.goto("http://localhost:3000/dashboard")
    page.get_by_role("button", name="New API key").click()
    page.screenshot(path="static/img/docs/new-api-key.png")
    browser.close()
# Runs in the same CI job as the docs build → the screenshot can never
# describe a version of the UI that no longer exists.

You  Here is the draft. Build the visual plan, illustrate it, and open a PR.
     Charts only from numbers already in the text.

Agent  → plan: hero=photo · §2=chart · §3=diagram · §4=photo
      → search_photos(q="a developer working late at a desk with two
         monitors and a mechanical keyboard in a dark room…")
      ← 16 photos · 147 ms · picked #1, 3000×1688, credited
      → mermaid-cli build/graph.mmd → static/img/graph.svg
      → chart.py §2 → 4 values checked against the draft ✓
      → search_photos(q="two engineers standing at a whiteboard…")
      ← 16 photos · 144 ms · picked #1

      ✓ 4 slots filled · 2 API calls · alt + credit + ImageObject written
      ⚠ §5 returned nothing above 0.5 — brief too abstract, rewritten as
        "a person at a kitchen table checking figures on a laptop"