Agent-Skills.md

Agent Skills: Generate Illustrations with Gemini

Analyze content and generate illustrations via Gemini image API

UncategorizedID: idvorkin/chop-conventions/gen-image

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idvorkin/chop-conventions
idvorkin

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pnpm dlx add-skill https://github.com/idvorkin/chop-conventions/tree/HEAD/skills/gen-image

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skills/gen-image/SKILL.md

Skill Metadata

Name
gen-image
Description
"Analyze content and generate illustrations via Gemini image API"

Generate Illustrations with Gemini

Analyze a blog post or topic, propose illustrations, and generate them via the Gemini image generation API.

Arguments

Parse the user's input for:

  • Target: A file path (e.g., _d/four-healths.md) or a freeform topic (e.g., "meditation benefits")
  • --style 'description': Override the default illustration style entirely
  • --ref 'path': One or more reference images for character consistency (can be repeated). When using the default raccoon style, always pass the canonical reference image (see below) unless the user opts out
  • --api-url 'url': Override the Gemini API endpoint (default below)
  • --count N: Max number of images to generate (default: 3)
  • --aspect 'W:H': Aspect ratio via imageConfig (default: 3:4, portrait). Valid values: 1:1, 2:3, 3:2, 3:4, 4:3, 4:5, 5:4, 9:16, 16:9, 21:9
  • --transparent: Generate on a uniform magenta background, then strip it via Recraft's removeBackground API. Soft-mask edges on hair/fur, no flood-fill / corner-seed failure modes, and works on AI outputs with irregular edges. Cost: ~$0.01/call. Latency: ~7-40s/call. Requires: RECRAFT_API_TOKEN in env or ~/.env and a network connection. After the strip, two layered evals auto-run — see Automatic eval below.
  • --fast / --no-fast: Pick the Gemini image-generation model. Default is --fast (gemini-3.1-flash-image-preview) — cheaper, lower latency, the historical behavior. --no-fast swaps in gemini-3-pro-image-preview (Pro), which is more obedient to style directives but slower and more expensive. Use --no-fast when Flash is ignoring or mangling specific instructions in the prompt (shirt text, exact framing, character details). The selected model is passed to gemini-image.sh via the GEMINI_IMAGE_MODEL env var.
  • --no-eval: Skip the alpha-mask eval pass that looks for interior holes and edge fringe (needs numpy/pillow/scipy — the uv run --script shebang installs them automatically, but plain python3 invocations without uv may need this flag). The alpha-mean signal still runs.
  • --eval-strict: Exit nonzero when any alpha-mask eval threshold trips. Useful when a calling agent wants to retry or fail loudly instead of silently shipping a broken alpha mask.

Automatic eval

When --transparent is active, generate.py runs two complementary evals on the Recraft output and prints metrics to stderr. Both signals are bg-removal-mechanism-agnostic — they measure the alpha channel of the finished RGBA image, so they work as a regression guard against any future stripper too.

(1) Alpha-mean signal (evaluate_strip, always on — same thresholds test_generate.py asserts):

  • Status healthy — alpha mean in 15–85% band.
  • Status subject_eaten — alpha mean below 15%; the strip ate the subject. Recraft may have misidentified the subject — regenerate, or inspect the source.
  • Status nothing_stripped — alpha mean above 85%; subject fills the frame. Widen the crop.

(2) Alpha-mask quality signal (eval_alpha, opt-out via --no-eval):

  • interior_hole_px — pixels in transparent regions that only become enclosed once the opaque mask is morphologically closed by 1 pixel. Isolates bleed-through damage: thin 1–2-pixel channels through the character (neck, between fingers, limb outlines) that topologically connect a real interior hole to the outside background so a naive "enclosed transparent" check reports zero. Legitimate design gaps (armpit openings, space between legs) are wider than 2 px and stay unaffected by the closing, so they don't false-alarm.
  • interior_hole_largest_px — pixels in the single biggest channel-revealed hole. More stable across images; good thresholding target because one big visible hole is what a human notices.
  • edge_fringe_px — partial-alpha pixels (signals halo — a known Recraft tradeoff on hair/fur edges).

Output format:

eval [healthy] out.webp: alpha=51.3% size=74.0KB
[eval] /tmp/out.webp: holes=0 (largest=0), fringe=0   [OK]
[eval] /tmp/out.webp: holes=4508 (largest=4356), fringe=0   [WARN: interior damage likely — check alpha mask]

Thresholds for the mask-quality signal are conservative by default (holes > 500, fringe > 2000). Pass --no-eval to skip it. Pass --eval-strict to exit nonzero when a mask-quality threshold trips.

Why: visual inspection on a light or dark background hides interior damage (holes read as shadow/shading). The alpha mask is the ground truth. Baking both evals into the skill makes them the default, so a silently-broken output can't ship. See /hill-climbing for the "eval becomes regression guard" pattern.

Configuration

  • Auth (Gemini): GOOGLE_API_KEY — auto-loaded from ~/.env by generate.py
  • Auth (Recraft): RECRAFT_API_TOKEN — auto-loaded from ~/.env (tolerates export KEY=val form) by recraft_bg_remove.py. Required for --transparent (the only bg-removal path). Check the account balance any time with ./skills/gen-image/recraft_bg_remove.py balance (no credits consumed). Each strip costs ~$0.01.
  • Default style: Read from raccoon-style.txt (in this skill's directory) by generate.py
  • Reference image: Auto-resolved by generate.py (searches ~/gits/blog*/images/raccoon-nerd.webp)
  • Low-level scripts: gemini-image.sh handles single Gemini API calls; recraft_bg_remove.py (Typer + uv-shebang, stdlib-only HTTP layer) handles Recraft removeBackground calls. Both used internally by generate.py. The Recraft script honors the output extension: .webp is converted via cwebp -q 90 so file sizes and visuals match gemini-image.sh's direct WebP output.
  • Generation wrapper: ../image-explore/generate.py handles env loading, style, ref image, and parallel batch execution

When --style is provided, it replaces the default raccoon style entirely (it is not appended).

Recipes

Scene recipes that have been dialed in — pass the scene to generate.py single/batch with the noted flags.

Metal AI twin ("me and my AI")

The raccoon mascot beside a chrome metal twin of itself — an "AI" version of the mascot. Used as the blog's default AI-post image (raccoon-ai-native; see /raccoon-history).

  • Reference: --ref <blog>/images/raccoon-nerd.webp (the canonical mascot). A reference locks the shape far better than prose. Caveat: a ref also pulls its shirt text and incidental details, not just style — so state the shirt explicitly and negate the ref's, e.g. green t-shirt reading exactly 'YEAR OF WONDER' (NOT 'technologist').
  • Model: --no-fast (Gemini Pro) — Flash mangles multi-word shirt text.
  • Aspect: --aspect 3:4.
  • The twin (scene snippet): "a METAL TWIN of the exact same raccoon — identical chibi proportions and silhouette (same head, ears, snout, ringed tail, same scale), NOT a humanoid robot — cast in iridescent anodized chrome (shifting rainbow/oil-slick, not flat grey) with warm glowing eyes and thin glowing energy-seams along the joints and tail."
  • Why iridescent + glow: flat mirror-chrome reads "frozen"; iridescent metal + glowing eyes + energy-seams read "alive." The material does the emotional work.
  • Background: white for an og:image (transparent renders unpredictably on social cards); --transparent for an in-post float.

Workflow

Phase 1: Read & Analyze Content

If the target is a file path:

  1. Read the file
  2. Identify the main themes/sections
  3. Note any existing images (look for blob_image, local_image, image_float includes, and raw markdown images)
  4. Identify sections that would benefit from illustrations — prioritize sections that have no images yet

If the target is a freeform topic:

  1. Use it directly as the theme for image generation
  2. Skip the content analysis and go straight to Phase 2

Phase 2: Design Illustrations

For each illustration opportunity, prepare:

  • Section: Which part of the post it enhances (or "standalone" for topic-based)
  • Filename: Following the project convention — raccoon-{descriptor}.webp for raccoon style, {descriptor}.webp otherwise
  • Prompt: A detailed generation prompt that combines the style + the specific scene/action
    • For raccoon style, include a Shirt text: 'SOMETHING' directive relevant to the section
    • Include the aspect ratio in the prompt (e.g., "portrait orientation, 3:4 aspect ratio")

Present at most --count illustrations (default 3).

Phase 3: Confirm with User

Present the illustration plan as a table:

| # | Section | Filename | Prompt Summary | | --- | ------- | ----------------------- | ----------------------------------------------- | | 1 | Health | raccoon-kettlebell.webp | Raccoon lifting kettlebell, shirt: "FIT FELLOW" | | 2 | Family | raccoon-picnic.webp | Raccoon at family picnic, shirt: "FAMILY TIME" |

Ask the user to approve, modify, or remove items before generating. Use AskUserQuestion to confirm.

Phase 4: Generate Images

Use generate.py from the image-explore skill. It handles env loading (~/.env), raccoon style (from raccoon-style.txt), reference image resolution, and parallel batch execution automatically.

  1. Resolve the script path:

    CHOP_ROOT="$(cd "$(dirname "$(readlink -f ~/.claude/skills/gen-image/SKILL.md)")" && git rev-parse --show-toplevel)"
GEN="$CHOP_ROOT/skills/image-explore/generate.py"

  2. Single image:

    uv run "$GEN" single --scene "Raccoon lifting kettlebell in a gym" --shirt "FIT" --output raccoon-kettlebell.webp

    The script's PEP 723 shebang auto-installs deps (typer + numpy/pillow/scipy for the --transparent eval). Pass --aspect, --ref, or --style to override defaults. Under --transparent, pass --no-eval to skip the mask-quality eval on stock python3 callers without numpy/scipy, and --eval-strict to exit nonzero when any eval threshold trips.

  3. Multiple images (parallel): Write a JSON file and use batch mode:

    [
  {
    "scene": "Raccoon lifting kettlebell in a gym",
    "shirt": "FIT",
    "output": "raccoon-kettlebell.webp"
  },
  {
    "scene": "Raccoon at family picnic",
    "shirt": "FAMILY",
    "output": "raccoon-picnic.webp"
  }
]

    uv run "$GEN" batch illustrations.json --aspect 3:4

  4. After generation, show each image to the user by reading the file with the Read tool (which renders images inline).

  5. If generation fails, report the error and ask if the user wants to retry with a modified prompt or skip.

Auto-eval runs on every generation. When --transparent is set, generate.py runs two complementary evals right after the Recraft pass — the alpha-mean signal (always) and the alpha-mask quality signal (interior holes, edge fringe; opt-out via --no-eval). Details and thresholds in the Automatic eval subsection above. See /hill-climbing for the "eval becomes regression guard" pattern.

Verifying transparent output. Don't judge bg-strip quality by compositing on a solid background — interior holes read as the background color. Extract the alpha channel as a mask: magick out.webp -alpha extract mask.png. A clean mask is a solid silhouette; swiss-cheese holes or visible halo mean the strip mis-segmented the subject.

Phase 5: Insert References (Optional)

Ask the user if they want the images inserted into the post. If yes:

  • For images stored in the blog's assets/images/ directory, use:

    {% include local_image_float_right.html src="filename.webp" %}

  • For images stored in the external blob repo (idvorkin/blob), use:

    {% include blob_image_float_right.html src="blog/filename.webp" %}

  • Insert the include tag just below the relevant section header (after any front matter or introductory text)

If the target was a freeform topic (not a file), skip this phase — just tell the user where the files were saved.

Output Directory

  • If editing a blog post, save images to the same directory convention the blog uses (ask user if unsure)
  • If freeform topic, save to ~/tmp/ and tell the user the paths

Error Handling

  • Missing API key: generate.py auto-loads from ~/.env. If still missing, tell the user to set GOOGLE_API_KEY
  • API error: Show the error message, suggest checking the API key or endpoint
  • No jq: The helper script (gemini-image.sh) requires jq
  • No cwebp: Images will be saved as PNG instead of WebP — inform the user

Safety

  • Always confirm before generating (API calls cost money)
  • Never generate more than 5 images in a single run without explicit user approval
  • Show each generated image to the user for review