sg-generate-images

name	sg-generate-images
effort	low
description	Generate slide visuals using Gemini Pro from validated graphics descriptions. Use when you want to generate slide images, create visuals after validation, or see what the slides will look like.
argument-hint	<presentation.md> [--resolution high|medium|small]
allowed-tools	Bash, Read, Glob, Grep

Slide Generator: Generate Images Step

Generate slide visuals using Gemini Pro from the validated graphics descriptions in the presentation. Uses a unified prompt builder and async batch generation for efficiency.

Pre-loaded Context

Working directory: !pwd

Available presentation files: !ls -la *.md 2>/dev/null | grep -i pres || echo "No presentation files found"

Existing images: !ls -la images/ 2>/dev/null || echo "No images directory yet"

Prerequisites

• Preflight: sg --version must succeed before proceeding — if sg is missing, stop and tell the user this requires the private davistroy/slide-generator engine (owner-only; see ADR-0008)
• slide-generator package installed
• GOOGLE_API_KEY set in environment (Gemini Pro access)
• A presentation.md file with validated graphics descriptions
• Graphics validation should be run first (.graphics_validated marker)

Input Validation

Required:

• <presentation.md> - Path to presentation markdown file

Optional:

• --resolution <level> - Image resolution: small, medium, high (default: high)
• --image-format <fmt> - Output format: png, jpg (default: png)
• --skip-existing - Don't regenerate images that already exist

Instructions

1. Verify prerequisites: Confirm GOOGLE_API_KEY is set and presentation has validated graphics
2. Run image generation:

   sg generate-images presentation.md --resolution high
   

3. Monitor progress: Image generation takes time (~5-10s per image)
4. Verify output: Check that images were created in the images/ directory
5. Report results: Show count of images generated, any failures

How It Works

The image generation step uses:

• Gemini Pro (gemini-3-pro-image-preview): Google's image generation model
• Unified prompt builder: prompt_builder.py constructs optimized prompts from descriptions
• Async batch generation: Multiple images generated concurrently via asyncio
• API key in header: Authentication via header (not query param)
• Block reason diagnostics: Clear error messages when generation is blocked

Error Handling

Error	Cause	Fix
GOOGLE_API_KEY not found	Missing env var	Set the key
Image blocked	Content policy violation	Review and soften the description
Rate limit	Too many concurrent requests	Built-in rate limiter handles this
Generation timeout	Gemini service slow	Retry; increase SG_API_TIMEOUT

Cost Estimate

• ~$0.10 per image at high resolution
• Typical 20-slide deck: ~$2.00

Output

The step produces:

• PNG/JPG images in an images/ directory (one per slide)
• File names correspond to slide numbers (slide-01.png, slide-02.png, etc.)

Next Step

After images are generated, build the final PowerPoint:

sg build presentation.md --template generic

Or use /sg-build to continue the pipeline.

Related Gemini Image Path

This step delegates image generation to the external sg CLI (the slide-generator package), which is unbundled and maintained outside this repo. personal-plugin's visual-explainer skill/tool is a separate, in-tree, tested Gemini image path with its own prompt builder and model config — the two are intentionally independent implementations, not a shared library. Future Gemini model or API changes (e.g. a new model ID, auth scheme, or block-reason handling) must be applied in both places: here (via the external sg package) and in plugins/personal-plugin/tools/visual-explainer/.