Gemini Image Generator

Overview

Generate images using Google's Gemini API with support for text-to-image generation, image editing, and multi-image reference inputs. Supports both the fast Gemini 2.5 Flash model and the high-quality Gemini 3 Pro model with up to 4K resolution.

When to Use

Generating app icons, logos, and UI assets
Creating marketing visuals and promotional graphics
Prototyping UI designs with AI-generated placeholders
Generating game sprites and 2D assets
Creating concept art and mood boards
Editing or modifying existing images with text prompts
Style transfer using reference images

Prerequisites

Python 3.9+
```
google-genai
```
package
```
GEMINI_API_KEY
```
environment variable

Installation

bash

pip install google-genai

Getting an API Key

Go to Google AI Studio
Sign in with your Google account
Click "Create API Key"
Copy the key and set it as an environment variable:

bash

export GEMINI_API_KEY="your-api-key"

Add to your shell profile (

~/.zshrc

~/.bashrc

) for persistence:

bash

echo 'export GEMINI_API_KEY="your-api-key"' >> ~/.zshrc

Quick Start

Generate a simple image:

bash

python scripts/generate_image.py -p "A fluffy orange cat sitting on a windowsill, warm sunlight, cozy atmosphere"

Generate with specific aspect ratio:

bash

python scripts/generate_image.py -p "Modern tech startup banner" -a 16:9 -o banner.png

Edit an existing image:

bash

python scripts/generate_image.py -p "Make the sky more dramatic with sunset colors" -i photo.jpg -o edited.png

Command Reference

python scripts/generate_image.py [options]

Required:
  -p, --prompt TEXT         Text prompt describing the image

Optional:
  -o, --output PATH         Output file path (default: auto-generated)
  -m, --model MODEL         Model to use (default: gemini-3-pro-image-preview)
  -a, --aspect-ratio RATIO  Aspect ratio (default: 1:1)
  -s, --size SIZE           Image size: 1K, 2K, 4K (default: 1K, Pro only)
  -i, --input-image PATH    Input image for editing mode
  -r, --reference-images    Reference image(s), can be repeated (max 14)
  -v, --verbose             Show detailed progress

Models

Model	Resolution	Best For
`gemini-3-pro-image-preview`	Up to 4K	Final assets, high quality, professional work
`gemini-2.5-flash-image`	1024px	Quick iterations, prototyping, batch generation

The Pro model is used by default. Use the Flash model for faster generation when quality is less critical:

bash

python scripts/generate_image.py -p "Quick concept sketch" -m gemini-2.5-flash-image

Aspect Ratios

Ratio	Use Case
`1:1`	App icons, profile pictures, thumbnails
`2:3`	Portrait photos, book covers
`3:2`	Landscape photos, postcards
`3:4`	Portrait photos, social media posts
`4:3`	Traditional photos, presentations
`4:5`	Instagram posts, portrait social media
`5:4`	Large format prints
`9:16`	Stories, vertical videos, mobile wallpapers
`16:9`	Widescreen banners, video thumbnails, headers
`21:9`	Ultrawide banners, cinematic headers

Image Sizes

Available for Gemini 3 Pro model only:

Size	Resolution	Use Case
`1K`	1024px	Web graphics, thumbnails
`2K`	2048px	Print materials, detailed graphics
`4K`	4096px	High-resolution prints, large displays

bash

python scripts/generate_image.py -p "Detailed landscape" -s 4K -o landscape_4k.png

Prompt Engineering Guide

Prompt Structure

Use this formula for effective prompts:

[Subject] + [Style] + [Details] + [Quality modifiers]

Techniques

1. Be Specific About the Subject

Bad:  "a cat"
Good: "a fluffy orange tabby cat sitting on a windowsill"

2. Specify Art Style

Photorealistic, cartoon, anime, oil painting, watercolor
Digital art, 3D render, pixel art, vector illustration
Specific styles: "in the style of Studio Ghibli", "cyberpunk aesthetic"

3. Include Environment and Lighting

"golden hour lighting", "dramatic shadows", "soft ambient light"
"neon-lit cityscape", "cozy interior", "misty forest"

4. Add Quality Modifiers

"high quality", "detailed", "professional"
"sharp focus", "studio lighting", "cinematic"

5. Specify Composition

"centered composition", "rule of thirds"
"close-up", "wide shot", "bird's eye view", "isometric"

Example Prompts by Use Case

App Icon

Minimalist app icon for a weather app, blue gradient background,
white cloud with golden sun rays, flat design, rounded corners,
iOS style, clean and modern

Marketing Banner

Professional tech startup banner, abstract geometric shapes
flowing from left to right, purple and blue gradient,
modern and clean aesthetic, corporate style

Game Sprite

Pixel art character sprite, fantasy warrior with glowing sword,
32x32 style, transparent background, retro 16-bit game aesthetic,
vibrant colors

Product Photo

Professional product photo of wireless earbuds on white background,
soft shadows, studio lighting, minimalist composition,
commercial photography style

Concept Art

Futuristic city skyline at sunset, flying vehicles between
towering skyscrapers, neon lights reflecting on wet streets,
cyberpunk atmosphere, cinematic composition, detailed

UI Mockup Asset

Abstract gradient background for mobile app, soft purple to pink
transition, subtle geometric patterns, modern and minimal,
suitable for dark text overlay

Generation Modes

Text-to-Image

Generate images from text descriptions:

bash

python scripts/generate_image.py -p "Your description here" -o output.png

Image Editing

Modify an existing image with a text prompt:

bash

python scripts/generate_image.py \
  -p "Change the background to a tropical beach at sunset" \
  -i original.jpg \
  -o edited.png

Multi-Image Reference

Use up to 14 reference images to guide style or content:

bash

python scripts/generate_image.py \
  -p "Create a new character in this art style" \
  -r style_ref1.png \
  -r style_ref2.png \
  -o new_character.png

Examples

Generate App Icons

bash

# iOS-style weather icon
python scripts/generate_image.py \
  -p "Minimalist weather app icon, blue sky gradient, white fluffy cloud, sun peeking out, flat design, rounded square, iOS 17 style" \
  -a 1:1 \
  -o weather_icon.png

# Fitness app icon
python scripts/generate_image.py \
  -p "Fitness app icon, running figure silhouette, orange to red gradient background, energetic and dynamic, modern flat design" \
  -a 1:1 \
  -o fitness_icon.png

Create Marketing Assets

bash

# Website hero banner
python scripts/generate_image.py \
  -p "Abstract tech hero banner, flowing data visualization, dark blue background with glowing cyan accents, futuristic and professional" \
  -a 21:9 \
  -s 2K \
  -o hero_banner.png

# Social media post
python scripts/generate_image.py \
  -p "Motivational quote background, soft sunrise gradient, minimalist mountain silhouette, peaceful and inspiring" \
  -a 4:5 \
  -o social_post_bg.png

Generate Game Assets

bash

# Character sprite
python scripts/generate_image.py \
  -p "Pixel art hero character, knight with blue cape and silver armor, idle pose, transparent background, 16-bit retro style" \
  -a 1:1 \
  -o knight_sprite.png

# Environment tile
python scripts/generate_image.py \
  -p "Grass tile for top-down RPG, seamless pattern, vibrant green with small flowers, pixel art style, 32x32 aesthetic" \
  -a 1:1 \
  -o grass_tile.png

Edit Photos

bash

# Change background
python scripts/generate_image.py \
  -p "Replace background with a cozy coffee shop interior" \
  -i portrait.jpg \
  -o portrait_coffee_shop.png

# Style enhancement
python scripts/generate_image.py \
  -p "Enhance with dramatic cinematic color grading, increase contrast, add film grain" \
  -i landscape.jpg \
  -o landscape_cinematic.png

Troubleshooting

"GEMINI_API_KEY environment variable not set"

Set your API key:

bash

export GEMINI_API_KEY="your-api-key"

"Rate limit exceeded"

Wait a few minutes and try again. For batch operations, add delays between requests.

"Content policy violation"

Modify your prompt to avoid content that violates Google's usage policies. Try:

Using more generic descriptions
Avoiding specific brand names or copyrighted characters
Removing potentially sensitive content

"No image in response"

The model sometimes returns text instead of an image. Try:

Making your prompt more specific
Adding "generate an image of" to your prompt
Using a different aspect ratio

"Unsupported image format"

Supported formats for input images: PNG, JPEG, WebP

Size option not working

The size option (2K, 4K) is only available for

gemini-3-pro-image-preview

. The Flash model always generates 1024px images.

Best Practices

Start simple: Begin with clear, concise prompts and iterate
Use the right model: Flash for speed, Pro for quality
Match aspect ratio to use case: 16:9 for banners, 1:1 for icons
Save high-quality versions: Use 4K when you need detailed assets
Iterate on prompts: Small changes can significantly affect results
Use reference images: For consistent style across multiple generations
Add quality modifiers: "high quality", "detailed", "professional"
Specify what you don't want: "no text", "simple background", "no people"

gemini-image-generator

NPX Install

Tags

SKILL.md Content

Gemini Image Generator

Overview

When to Use

Prerequisites

Installation

Getting an API Key

Quick Start

Command Reference

Models

Aspect Ratios

Image Sizes

Prompt Engineering Guide

Prompt Structure

Techniques

Example Prompts by Use Case

Generation Modes

Text-to-Image

Image Editing

Multi-Image Reference

Examples

Generate App Icons

Create Marketing Assets

Generate Game Assets

Edit Photos

Troubleshooting

"GEMINI_API_KEY environment variable not set"

"Rate limit exceeded"

"Content policy violation"

"No image in response"

"Unsupported image format"

Size option not working

Best Practices