Generate Command

Generate images from text prompts with optional reference images using Google Gemini models.

Alias: generate-image (can be used interchangeably with generate)

Usage

gemini-nano-banana-tool generate [PROMPT] -o OUTPUT [OPTIONS]
gemini-nano-banana-tool generate-image [PROMPT] -o OUTPUT [OPTIONS]  # Alias

Arguments

• PROMPT - Text prompt (positional, mutually exclusive with -f and -s)

Required Options

• -o, --output PATH - Output image file path (required)

Prompt Input Options (mutually exclusive)

• PROMPT - Positional argument (default)
• -f, --prompt-file PATH - Read prompt from file
• -s, --stdin - Read prompt from stdin (for piping)

Image Options

• -i, --image PATH - Reference image (can be used up to 3 times for Flash, 14 for Pro)
• -a, --aspect-ratio TEXT - Aspect ratio (default: 1:1)
• -m, --model TEXT - Gemini model (default: gemini-2.5-flash-image)
• -r, --resolution TEXT - Resolution quality for Pro model (1K/2K/4K)

Authentication Options

• --api-key TEXT - Override API key from environment
• --use-vertex - Use Vertex AI instead of Developer API
• --project TEXT - Google Cloud project (for Vertex AI)
• --location TEXT - Google Cloud location (for Vertex AI)

Other Options

• -v, --verbose - Multi-level verbosity (-v INFO, -vv DEBUG, -vvv TRACE)

Examples

Basic Text-to-Image

# Simple generation (both commands work)
gemini-nano-banana-tool generate "A cat wearing a wizard hat" -o cat.png
gemini-nano-banana-tool generate-image "A cat wearing a wizard hat" -o cat.png

# With aspect ratio
gemini-nano-banana-tool generate "Mountain landscape" -o landscape.png -a 16:9

Prompt from File or Stdin

# From file
gemini-nano-banana-tool generate -f prompt.txt -o output.png

# From stdin (piping)
echo "Beautiful sunset" | gemini-nano-banana-tool generate -o sunset.png -s

# With promptgen
gemini-nano-banana-tool promptgen "wizard cat" | \
  gemini-nano-banana-tool generate -o cat.png -s -a 16:9

Image Editing with Reference Images

# Single reference image
gemini-nano-banana-tool generate "Add a birthday hat" -o edited.png \
  -i original.jpg

# Multiple reference images
gemini-nano-banana-tool generate "Put the dress on the model in garden" \
  -o fashion.png -i dress.jpg -i model.jpg

# Up to 3 references (Flash) or 14 (Pro)
gemini-nano-banana-tool generate "Combine these styles" -o result.png \
  -i ref1.jpg -i ref2.jpg -i ref3.jpg

Different Aspect Ratios

# Square (Instagram post)
gemini-nano-banana-tool generate "Modern design" -o square.png -a 1:1

# Widescreen (YouTube thumbnail)
gemini-nano-banana-tool generate "Epic scene" -o wide.png -a 16:9

# Vertical (Instagram story)
gemini-nano-banana-tool generate "Portrait" -o vertical.png -a 9:16

# Cinematic (ultra-wide)
gemini-nano-banana-tool generate "Sci-fi panorama" -o cinema.png -a 21:9

Model Selection and Resolution

# Default Flash model (fast, cost-effective)
gemini-nano-banana-tool generate "Your prompt" -o output.png

# Pro model (higher quality)
gemini-nano-banana-tool generate "Your prompt" -o output.png \
  -m gemini-3-pro-image-preview

# Pro with 4K resolution (maximum quality)
gemini-nano-banana-tool generate "Your prompt" -o output.png \
  -m gemini-3-pro-image-preview -r 4K

Verbosity Levels

# Normal (warnings only)
gemini-nano-banana-tool generate "test" -o output.png

# Verbose (show operations)
gemini-nano-banana-tool generate "test" -o output.png -v

# Debug (detailed info)
gemini-nano-banana-tool generate "test" -o output.png -vv

# Trace (full HTTP logs)
gemini-nano-banana-tool generate "test" -o output.png -vvv

Output Format

Returns JSON with generation details:

{
  "output_path": "output.png",
  "model": "gemini-2.5-flash-image",
  "aspect_ratio": "16:9",
  "resolution": "1344x768",
  "resolution_quality": "1K",
  "reference_image_count": 0,
  "token_count": 1295,
  "estimated_cost_usd": 0.0389,
  "metadata": {
    "finish_reason": "STOP",
    "safety_ratings": null
  }
}

Cost Information

Automatic cost tracking based on token usage:

• Flash Model: ~$0.039 per image (1,290 tokens × $0.00003)
• Pro Model 1K/2K: ~$0.134 per image (1,120 tokens × $0.00012)
• Pro Model 4K: ~$0.24 per image (2,000 tokens × $0.00012)

Cost is always included in output JSON as estimated_cost_usd.

Supported Aspect Ratios

• 1:1 - Square (1024×1024)
• 16:9 - Widescreen (1344×768)
• 9:16 - Vertical (768×1344)
• 4:3 - Traditional (1184×864)
• 3:4 - Portrait (864×1184)
• 3:2 - DSLR (1248×832)
• 2:3 - Portrait photo (832×1248)
• 21:9 - Cinematic (1536×672)
• 4:5 - Instagram portrait (896×1152)
• 5:4 - Medium format (1152×896)

Authentication

Set environment variable:

export GEMINI_API_KEY='your-api-key'

Get API key: https://aistudio.google.com/app/apikey

For Vertex AI:

export GOOGLE_GENAI_USE_VERTEXAI=true
export GOOGLE_CLOUD_PROJECT='your-project-id'
export GOOGLE_CLOUD_LOCATION='us-central1'