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4. Set up API key

mkdir -p ~/.nano-banana

echo "GEMINI_API_KEY=" > ~/.nano-banana/.env

After init, the user can type `nano-banana "prompt"` from anywhere.

If `bun link` fails or the command is not found after linking, fall back to:

mkdir -p ~/.local/bin

ln -sf ~/tools/nano-banana-2/src/cli.ts ~/.local/bin/nano-banana

Then ensure ~/.local/bin is on PATH:

echo 'export PATH="$HOME/.local/bin:$PATH"' >> ~/.zshrc

source ~/.zshrc


Get a Gemini API key at: [https://aistudio.google.com/apikey](https://aistudio.google.com/apikey)

## Quick Reference

- Command: `nano-banana "prompt" [options]`

- Default: 1K resolution, Flash model, current directory

## Core Options

Option
Default
Description

`-o, --output`
`nano-gen-{timestamp}`
Output filename (no extension)

`-s, --size`
`1K`
Image size: `512`, `1K`, `2K`, or `4K`

`-a, --aspect`
model default
Aspect ratio: `1:1`, `16:9`, `9:16`, `4:3`, `3:4`, etc.

`-m, --model`
`flash`
Model: `flash`/`nb2`, `pro`/`nb-pro`, or any model ID

`-d, --dir`
current directory
Output directory

`-r, --ref`
-
Reference image (can use multiple times)

`-t, --transparent`
-
Generate on green screen, remove background (FFmpeg)

`--api-key`
-
Gemini API key (overrides env/file)

`--costs`
-
Show cost summary

## Models

Alias
Model
Use When

`flash`, `nb2`
Gemini 3.1 Flash
Default. Fast, cheap (~$0.067/1K image)

`pro`, `nb-pro`
Gemini 3 Pro
Highest quality needed (~$0.134/1K image)

## Sizes

Size
Cost (Flash)
Cost (Pro)

`512`
~$0.045
Flash only

`1K`
~$0.067
~$0.134

`2K`
~$0.101
~$0.201

`4K`
~$0.151
~$0.302

## Aspect Ratios

Supported: `1:1`, `16:9`, `9:16`, `4:3`, `3:4`, `3:2`, `2:3`, `4:5`, `5:4`, `21:9`

Use `-a` flag: `nano-banana "cinematic scene" -a 16:9`

## Key Workflows

### Basic Generation

nano-banana "minimal dashboard UI with dark theme"

nano-banana "cinematic landscape" -s 2K -a 16:9

nano-banana "quick concept sketch" -s 512


### Model Selection

Default (Flash - fast, cheap)

nano-banana "your prompt"

Pro (highest quality)

nano-banana "detailed portrait" --model pro -s 2K


### Reference Images (Style Transfer / Editing)

Edit existing image

nano-banana "change the background to pure white" -r dark-ui.png -o light-ui

Style transfer - multiple references

nano-banana "combine these two styles" -r style1.png -r style2.png -o combined


### Transparent Assets

nano-banana "robot mascot character" -t -o mascot

nano-banana "pixel art treasure chest" -t -o chest


The `-t` flag automatically prompts the AI to generate on a green screen, then uses FFmpeg `colorkey` + `despill` to key out the background and remove green spill from edge pixels. Pixel-perfect transparency with no manual prompting needed.

Requires: `brew install ffmpeg imagemagick`

### Exact Dimensions

To get a specific output dimension:

- First `-r` flag: your reference/style image

- Last `-r` flag: blank image in target dimensions

- Include dimensions in prompt

nano-banana "pixel art character in style of first image, 256x256" -r style.png -r blank-256x256.png -o sprite


## Reference Order Matters

- First reference: primary style/content source

- Additional references: secondary influences

- Last reference: controls output dimensions (if using blank image trick)

## Cost Tracking

Every generation is logged to `~/.nano-banana/costs.json`. View summary:

nano-banana --costs


## Use Cases

- **Landing page assets** - product mockups, UI previews

- **Image editing** - transform existing images with prompts

- **Style transfer** - combine multiple reference images

- **Marketing materials** - hero images, feature illustrations

- **UI iterations** - quickly generate variations of designs

- **Transparent assets** - icons, logos, mascots with no background

- **Game assets** - sprites, backgrounds, characters

- **Video production** - visual elements for video compositions

## Prompt Examples

UI mockups

nano-banana "clean SaaS dashboard with analytics charts, white background"

Widescreen cinematic

nano-banana "cyberpunk cityscape at sunset" -a 16:9 -s 2K

Product shots with Pro quality

nano-banana "premium software product hero image" --model pro

Quick low-res concept

nano-banana "rough sketch of a robot" -s 512

Dark mode UI

nano-banana "Premium SaaS chat interface, dark mode, minimal, Linear-style aesthetic"

Game assets with transparency (green screen auto-prompted)