ZenMux Image Gen (Nano Banana 2)

Generate images from text prompts using ZenMux API (Vertex AI protocol with Gemini models). Use when: (1) User wants to generate/create images from text desc...

ZenMux Image Generation

Generate images from text prompts using ZenMux API with Google Gemini models.

Quick Start

# Generate image (requires ZENMUX_API_KEY env var)
python3 scripts/generate_image.py "A cute cat" output.png

# With aspect ratio and resolution
python3 scripts/generate_image.py "A cute cat" output.png --aspect-ratio 16:9 --image-size 2K

API Key Setup

Get your API key from https://zenmux.ai.

# Set environment variable
export ZENMUX_API_KEY="sk-..."

Security Rules:

• NEVER use --api-key flag (visible in shell history)
• NEVER commit API keys to git

Script Options

Option	Description
--model MODEL	Model name (default: google/gemini-3.1-flash-image-preview)
--input-image PATH	Input image for image-to-image generation
--temperature N	Randomness 0.0-2.0 (default: 1.0)
--max-tokens N	Max output tokens
--aspect-ratio RATIO	1:1, 2:3, 3:2, 3:4, 4:3, 9:16, 16:9, 21:9
--image-size SIZE	1K (default), 2K, 4K

Image-to-Image

Edit existing images with text prompts:

python3 scripts/generate_image.py "Make it nighttime" result.png --input-image photo.jpg

Available Models

Model	Alias	Use Case
google/gemini-3.1-flash-image-preview	Nano Banana 2	Fast & quality (default)
google/gemini-3-pro-image-preview	Nano Banana Pro	Best quality
google/gemini-2.5-flash-image	Nano Banana	Faster generation

Prompt Tips

Writing effective prompts:

• Be specific: "A golden retriever puppy playing on grass" instead of "a dog"
• Include details: lighting (golden hour, soft light), style (photorealistic, anime, oil painting)
• For image-to-image: describe the desired change clearly, e.g., "Change to nighttime with city lights"
• Try 10+ words for better results

Troubleshooting

Error	Fix
Input image not found	Check file path; verify file exists
Image too large	Max input size is 20 MB; compress before uploading
401 Unauthorized	Check ZENMUX_API_KEY is set correctly
429 Rate limited	Wait and retry, or upgrade to paid tier
Request timeout	API may be slow; wait and retry
Network error	Check internet connection
No image in response	Try a different prompt or model
Poor image quality	Use more descriptive prompt (10+ words)

Script Features

• Timeout protection: Requests timeout after 300 seconds (5 minutes)
• Auto-create directories: Output directories are created automatically
• Auto-rename on conflict: If output file exists, automatically appends number (e.g., image_1.png, image_2.png)
• Input validation: Checks image format, size, and existence
• Clear error messages: Human-readable error explanations
• Format support: JPG, PNG, WebP, GIF input formats

Batch Generation

Generate multiple images by running the script multiple times with different outputs:

# Generate variations of the same prompt
for i in 1 2 3; do
  python3 scripts/generate_image.py "A cute cat in different poses" "cat_$i.png"
done