image-generator

Image Generator

This skill generates and edits images using Google's Gemini Nano Banana Pro model (gemini-3-pro-image-preview).

IMPORTANT: Setup Required

Before using this skill, the user must set the GEMINI_API_KEY environment variable:

1. Get a free API key from Google AI Studio
2. Export the key in your shell profile (~/.zshrc, ~/.bashrc, etc.):

   export GEMINI_API_KEY="your_api_key_here"
   

3. Restart your terminal or run source ~/.zshrc (or ~/.bashrc)

The skill will not work without this configuration.

Pre-flight Check

Before making any API call, verify the key is set:

if [ -z "$GEMINI_API_KEY" ]; then
  echo "ERROR: GEMINI_API_KEY is not set. Please export it in your shell profile."
  exit 1
fi

If the key is missing, stop and tell the user to set it using the instructions above.

Configuration

Model: gemini-3-pro-image-preview

API Key: Read from the GEMINI_API_KEY environment variable

Iterating on User-Provided Images

When the user provides a path to an image they want to edit or iterate on, use this workflow:

Step 1: Read and encode the image to base64

# Get the image path from user
IMG_PATH="/path/to/user/image.png"

# Detect mime type
if [[ "$IMG_PATH" == *.png ]]; then
    MIME_TYPE="image/png"
elif [[ "$IMG_PATH" == *.jpg ]] || [[ "$IMG_PATH" == *.jpeg ]]; then
    MIME_TYPE="image/jpeg"
elif [[ "$IMG_PATH" == *.webp ]]; then
    MIME_TYPE="image/webp"
else
    MIME_TYPE="image/png"
fi

# Encode to base64 (works on both macOS and Linux)
if [[ "$(uname)" == "Darwin" ]]; then
    IMG_BASE64=$(base64 -i "$IMG_PATH")
else
    IMG_BASE64=$(base64 -w0 "$IMG_PATH")
fi

Step 2: Send image with edit prompt (File-Based Approach)

IMPORTANT: Always use a file-based approach for the request body. Base64-encoded images are too large for command-line arguments and will cause "argument list too long" errors.

# User's edit request
EDIT_PROMPT="Add a santa hat to the person in this image"

# Write request to a JSON file (avoids command line length limits)
cat > /tmp/gemini_request.json << JSONEOF
{
  "contents": [{
    "parts": [
      {"text": "$EDIT_PROMPT"},
      {
        "inline_data": {
          "mime_type": "$MIME_TYPE",
          "data": "$IMG_BASE64"
        }
      }
    ]
  }],
  "generationConfig": {
    "responseModalities": ["TEXT", "IMAGE"]
  }
}
JSONEOF

# Call the API using the file
curl -s -X POST \
  "https://generativelanguage.googleapis.com/v1beta/models/gemini-3-pro-image-preview:generateContent" \
  -H "x-goog-api-key: $GEMINI_API_KEY" \
  -H "Content-Type: application/json" \
  -d @/tmp/gemini_request.json > /tmp/gemini_response.json