onyx-dot-app/image-generation

Image Generation Skill

Generate images using Nano Banana (Google Gemini Image API). Supports text-to-image and image-to-image generation with configurable options.

Setup

Dependencies

pip install google-genai Pillow

Environment Variable

Set your API key:

export GEMINI_API_KEY="your_api_key_here"

Usage

Basic Text-to-Image

python scripts/generate.py --prompt "A futuristic city at sunset with neon lights" --output city.png

With Aspect Ratio

python scripts/generate.py \
  --prompt "Mountain landscape with a lake" \
  --output landscape.png \
  --aspect-ratio 16:9

Image-to-Image Mode

Use a reference image to guide generation:

python scripts/generate.py \
  --prompt "Make it look like a watercolor painting" \
  --input-image original.png \
  --output watercolor.png

Generate Multiple Images

python scripts/generate.py \
  --prompt "Abstract colorful art" \
  --output art.png \
  --num-images 3

Arguments

| Argument | Short | Required | Default | Description | |----------|-------|----------|---------|-------------| | --prompt | -p | Yes | — | Text prompt describing the desired image | | --output | -o | No | output.png | Output path for the generated image | | --model | -m | No | gemini-2.0-flash-preview-image-generation | Model to use for generation | | --input-image | -i | No | — | Reference image for image-to-image mode | | --aspect-ratio | -a | No | — | Aspect ratio: 1:1, 16:9, 9:16, 4:3, 3:4 | | --num-images | -n | No | 1 | Number of images to generate |

Available Models

• gemini-2.0-flash-preview-image-generation - Fast, optimized for speed and lower latency
• imagen-3.0-generate-002 - High quality image generation

Programmatic Usage

Import the function directly in Python:

from scripts.generate import generate_image

paths = generate_image(
    prompt="A serene mountain lake under moonlight",
    output_path="./outputs/lake.png",
    aspect_ratio="16:9",
    num_images=2,
)

Tips

• Detailed prompts work better: Instead of "a cat", try "a fluffy orange tabby cat sitting on a windowsill, soft morning light, photorealistic"
• Specify style: Include style keywords like "digital art", "oil painting", "photorealistic", "anime style"
• Use aspect ratios: Match the aspect ratio to your intended use (16:9 for landscapes, 9:16 for portraits/mobile)
• Image-to-image: Great for style transfer, variations, or guided modifications of existing images