Nano Banana - Gemini Image Generation

Generate images from text prompts via Google's Gemini image generation API.

When to Use

• User requests image generation, creation, or production from a text description
• Creating illustrations or visuals for presentations, articles, or documents
• Generating concept art, mockups, diagrams, or placeholder images
• Editing existing images with text instructions

Requirements

• GEMINI_API_KEY environment variable (get from https://ai.google.dev/)

Quick Start

Generate an image using the bundled script:

scripts/generate_image.sh "a minimalist flat illustration of a rocket" ./output.png

The script accepts three arguments:

1. Prompt (required) -- text description of the image
2. Output path (optional, default: ./generated_image.png)
3. Model (optional, default: gemini-2.5-flash-image)

Models

Workflow

Basic Generation

1. Craft a descriptive prompt (style + subject + composition + colors)
2. Run: scripts/generate_image.sh "prompt" ./path/to/output.png
3. Open result: open ./path/to/output.png

High-Quality Generation

For important or text-heavy images, specify the Pro model:

scripts/generate_image.sh "diagram showing..." ./diagram.png gemini-3-pro-image-preview

Image Editing

To edit an existing image, use the API directly with an input image. See references/api_reference.md for the request format including inlineData with base64-encoded source image.

Batch Generation

To generate multiple images, run the script in a loop:

for prompt in "prompt one" "prompt two" "prompt three"; do
  scripts/generate_image.sh "$prompt" "./output_$(date +%s).png"
done

Prompt Tips

• Specify visual style: "photograph", "flat illustration", "watercolor", "3D render"
• Include composition: "centered", "wide shot", "white background"
• Name colors: "blue and white color scheme", "warm earth tones"
• For text rendering, use Pro model and quote exact text: 'with the text "Hello"'

See references/api_reference.md for comprehensive prompt engineering guidance.

Resources

• scripts/generate_image.sh -- Main generation script. Handles API call, error reporting, base64 decoding, and file output.
• references/api_reference.md -- Full API documentation: endpoints, request/response formats, models, prompt tips, error codes.