Image Generation

Generate images from text prompts using OpenAI, Google Imagen, Nano Banana Pro (Gemini), or fal.ai.

Usage

OpenAI (gpt-image-1)

uv run ~/.claude/skills/image-gen/scripts/generate_openai.py \
  --prompt "a cat wearing a top hat" \
  --output /tmp/cat.png

Options:

• --prompt (required): Text description of the image
• --output, -o: Output file path (default: ./generated-{timestamp}.png)
• --size: Image size (default: 1024x1024, options: 1024x1024, 1024x1792, 1792x1024)
• --quality: Image quality (default: auto, options: low, medium, high, auto)

Google Imagen 4

uv run ~/.claude/skills/image-gen/scripts/generate_imagen.py \
  --prompt "a cat wearing a top hat" \
  --output /tmp/cat.png

Options:

• --prompt (required): Text description of the image
• --output, -o: Output file path (default: ./generated-{timestamp}.png)
• --model: Model to use (default: imagen-4.0-generate-001, options: imagen-4.0-fast-generate-001, imagen-4.0-ultra-generate-001)

Nano Banana Pro (Gemini)

uv run ~/.claude/skills/image-gen/scripts/generate_gemini.py \
  --prompt "a cat wearing a top hat" \
  --output /tmp/cat.png

Options:

• --prompt (required): Text description of the image
• --output, -o: Output file path (default: ./generated-{timestamp}.jpg)
• --model: Model to use (default: gemini-3-pro-image-preview)
• --aspect-ratio, -a: Aspect ratio (default: 1:1, options: 1:1, 16:9, 9:16, 21:9)
• --image-size, -s: Output size for Pro model (options: 1K, 2K, 4K)

fal.ai (Flux)

uv run ~/.claude/skills/image-gen/scripts/generate_fal.py \
  --prompt "a cat wearing a top hat" \
  --output /tmp/cat.png

Options:

• --prompt (required): Text description of the image
• --output, -o: Output file path (default: ./generated-{timestamp}.png)
• --model: Model to use (default: fal-ai/flux/dev)

Provider Comparison

Provider	Model	Speed	Quality	Cost
OpenAI	gpt-image-1	Medium	Excellent	~$0.04/img
Google	Imagen 4	Medium	Excellent	~$0.04/img
Google	Nano Banana Pro	Fast	Excellent	~$0.13/img (2K)
fal.ai	Flux dev	Fast	Very good	Pay-per-compute

Environment Variables

Provider	Variable	Required
OpenAI	OPENAI_API_KEY	Yes
Google	GOOGLE_API_KEY	Yes
fal.ai	FAL_KEY	Yes

Set in ~/.env or export in shell.

Troubleshooting

Getting API Keys

Provider	Get Key URL
OpenAI	https://platform.openai.com/api-keys
Google	https://aistudio.google.com/apikey
fal.ai	https://fal.ai/dashboard/keys

Common Errors

"API key not set"

# Add to ~/.env
echo "GOOGLE_API_KEY=your-key-here" >> ~/.env

# Or export in current shell
export GOOGLE_API_KEY=your-key-here

"API key is invalid"

• Regenerate your key at the provider's dashboard
• Ensure no extra whitespace when copying the key
• Check the key hasn't expired

"Rate limit exceeded"

• Wait 1-2 minutes and retry
• Check your usage quota at the provider's dashboard

"Content blocked"

• The prompt triggered safety filters
• Rephrase to avoid restricted content

"Cannot connect"

• Check your internet connection
• Verify the API service isn't experiencing outages

File Format Notes

• OpenAI: Returns PNG
• Google Imagen: Returns PNG
• Google Gemini: Returns JPEG (scripts auto-correct extension if needed)
• fal.ai Flux: Returns JPEG (scripts auto-correct extension if needed)

Testing

uv run ~/.claude/skills/image-gen/tests/test_image_gen.py --help