content-image-style

name	content-image-style
description	Image style reference — visual guidelines, prompt templates, placement rules, and file naming conventions for image generation. Reads project-specific values from plugin config.
user-invocable	false
disable-model-invocation	false

Image Style Reference

This skill provides the image generation rules for content creation. It is auto-loaded during image generation tasks.

Config Values

The following image_generation values are expected in your task prompt from the orchestrator:

• image_generation.enabled, image_generation.provider, image_generation.model, image_generation.guidelines
• image_generation.output_path, image_generation.hero_dimensions, image_generation.inline_dimensions
• image_generation.placement, image_generation.min_word_count, image_generation.skip_types
• image_generation.max_inline_images (optional — caps inline images per article)

For the full image style guide, read the file at image_generation.guidelines (e.g., .content-ops/image-style-guide.md). Below is the condensed reference for quick access.

Pre-Flight Checks

Before generating any images, verify:

1. image_generation.enabled is true — if not, skip entirely and note "image generation is disabled"
2. The content type is not in image_generation.skip_types — if it is, skip entirely
3. The article word count is at or above image_generation.min_word_count — if below, skip entirely
4. The required API key environment variable is set — check without printing the value:

   test -n "${GEMINI_API_KEY}" && echo "set" || echo "missing"
   

   Never echo, log, or include the API key in any output. If missing, stop with a clear error:
   • Gemini: GEMINI_API_KEY
   • OpenAI: OPENAI_API_KEY

Placement Decision Framework

When placement is ai-driven:

Always add:

• A hero image for every qualifying article (at the top, before the first paragraph)

Add a section image when the H2 section:

• Covers an abstract concept that benefits from visual representation
• Introduces a process, workflow, or comparison
• Is longer than ~150 words and not primarily a code block or numbered list

Skip a section image when:

• The section is a short factual statement
• The section already has code examples or step-by-step instructions (already visual enough)
• The section is the closing "next steps" or "related reading" section
• The section is very short (under 80 words)

Default approach: fewer, better-placed images beat one-per-section coverage. If image_generation.max_inline_images is set in config, respect that cap. Otherwise, use editorial judgment — typically 1–3 inline images for a standard article. Always defer to the image style guide at image_generation.guidelines for project-specific placement preferences.

API Call Patterns

Google Gemini (Nano Banana)

Use the model specified in image_generation.model from config. If not set, default to imagen-3.0-generate-002. Make API calls via Bash using curl:

# MODEL comes from image_generation.model in config (default: imagen-3.0-generate-002)
curl -s -X POST \
  "https://generativelanguage.googleapis.com/v1beta/models/${MODEL}:predict?key=${GEMINI_API_KEY}" \
  -H "Content-Type: application/json" \
  -d '{
    "instances": [{"prompt": "[your prompt here]"}],
    "parameters": {
      "sampleCount": 1,
      "aspectRatio": "[16:9 for inline | 1200:630 expressed as aspect ratio]",
      "outputMimeType": "image/webp"
    }
  }'

The response contains a base64-encoded image in predictions[0].bytesBase64Encoded. Decode and write to the output path.

OpenAI GPT Image

curl -s -X POST \
  "https://api.openai.com/v1/images/generations" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer ${OPENAI_API_KEY}" \
  -d '{
    "model": "${MODEL}",  // from image_generation.model in config (default: gpt-image-1)
    "prompt": "[your prompt here]",
    "n": 1,
    "size": "1792x1024",
    "response_format": "b64_json"
  }'

The response contains a base64-encoded image in data[0].b64_json.

Prompt Construction

Build prompts by combining three parts:

1. Content description — What the image should depict, derived from the article section's key concept
2. Style modifiers — From the Visual Style section of the image style guide
3. Base prompt template — From the Base Prompt Template section of the image style guide

Example assembled prompt:

A developer reviewing a distributed system architecture diagram on a laptop screen.
Flat illustration style, clean geometric shapes, bold outlines, minimal texture.
Primary color #1A1A2E accent color #E94560, neutral background, no text overlays,
no watermarks, professional quality, suitable for a blog article about microservices.

Keep prompts under 400 characters. Avoid vague terms like "beautiful" or "amazing" — be specific about what is depicted.

File Naming and Output

Output root:     {image_generation.output_path}/articles/{article-slug}/
Hero image:      hero.webp
Inline images:   {section-heading-slug}.webp (e.g., "## How Consensus Works" → how-consensus-works.webp)
Fallback format: .png (if API does not support webp)

Derive inline filenames by slugifying the H2 heading: lowercase, replace spaces and special characters with hyphens, collapse consecutive hyphens, trim leading/trailing hyphens. This makes filenames meaningful and aligned with the section content.

Write image bytes by piping the base64-decoded output via Bash:

echo "[base64 string]" | base64 -d > public/images/articles/{slug}/hero.webp

Always verify the file was written (check file size > 0) before returning the path.

Alt Text Rules

• Describe what the image depicts, not what it "is"
• Include the article topic keyword naturally
• Keep under 125 characters
• Do not start with "image of", "photo of", or "picture of"
• Write for screen readers — a blind user should understand what visual information they are missing

Examples:

Good: "A diagram showing how validator nodes reach consensus in a proof-of-stake network"
Bad:  "Image showing blockchain consensus"

Markdown Reference Format

Insert images as standard Markdown:

Hero image — insert after the closing --- of the frontmatter, before the first paragraph:

![{alt text}]({output_path}/articles/{slug}/hero.webp)

Inline section images — insert immediately before the ## Section Title heading they illustrate:

![{alt text}]({output_path}/articles/{slug}/{section-heading-slug}.webp)

## Section Title

Error Handling

• API rate limit (429): Retry up to 3 times with exponential backoff (2s, 4s, 8s). If still failing, skip the image and note it in the output.
• API key missing: Stop immediately with a clear error message. Do not attempt to generate.
• Network error: Retry once. If still failing, skip and note.
• Decode error (corrupted image): Skip and note. Do not write a broken file.

Always report skipped images clearly in the output so the orchestrator can flag them.