Gemini Imagen

Gemini Image Generation

Source: https://ai.google.dev/gemini-api/docs/image-generation

Google offers two approaches for image generation: Imagen (dedicated image model) and Gemini native (multimodal generation). All generated images include SynthID watermarks.

Model Selection

When to use which:

• Gemini native (gemini-*-image): Image editing, multi-turn refinement, mixed text+image output
• Imagen: Pure text-to-image, high-fidelity results, batch generation (1-4 images)

Quick Start

Gemini Native (Text-to-Image)

from google import genai
from PIL import Image

client = genai.Client()

response = client.models.generate_content(
    model="gemini-2.5-flash-image",
    contents=["A modern logo for a tech startup called 'Nexus'"],
)

for part in response.parts:
    if part.inline_data is not None:
        image = part.as_image()
        image.save("logo.png")

Imagen (Dedicated Image Generation)

from google import genai
from google.genai import types

client = genai.Client()

response = client.models.generate_images(
    model="imagen-4.0-generate-001",
    prompt="A photorealistic sunset over mountains, 4K HDR",
    config=types.GenerateImagesConfig(
        number_of_images=4,
        aspect_ratio="16:9",
    )
)

for i, generated_image in enumerate(response.generated_images):
    generated_image.image.save(f"sunset_{i}.png")

Image Editing (Gemini Native)

from google import genai
from PIL import Image

client = genai.Client()
source_image = Image.open("photo.jpg")

response = client.models.generate_content(
    model="gemini-2.5-flash-image",
    contents=[
        "Remove the background and replace with a gradient blue sky",
        source_image,
    ],
)

for part in response.parts:
    if part.inline_data is not None:
        part.as_image().save("edited.png")

Best Practices

Prompt Structure

Build prompts with three components:

1. Subject: The main object, person, or scene
2. Context: Background, setting, environment
3. Style: Art style, photography type, quality modifiers

"A [style] of [subject] in/with [context]"

Example:

"A minimalist logo for a health care company on a solid color background. Include the text 'Journey'."

Photography Modifiers

Text in Images

When generating text in images:

• Keep text under 25 characters for best results
• Use 2-3 distinct phrases maximum
• Specify font style (bold, serif, sans-serif)
• Specify placement (top, center, bottom)

prompt = 'A poster with the text "Summerland" in bold font as a title, underneath is "Summer never felt so good"'

Aspect Ratios

Imagen Configuration

config = types.GenerateImagesConfig(
    number_of_images=4,        # 1-4 images
    aspect_ratio="16:9",       # Aspect ratio
    image_size="2K",           # 1K or 2K (Ultra/Standard only)
    person_generation="allow_adult",  # dont_allow, allow_adult, allow_all
)

Multi-Turn Refinement (Gemini Native)

Gemini native supports conversational image editing:

from google import genai

client = genai.Client()
chat = client.chats.create(model="gemini-2.5-flash-image")

# Initial generation
response = chat.send_message("Create a cozy coffee shop interior")

# Iterative refinement
response = chat.send_message("Add more plants and warmer lighting")
response = chat.send_message("Make it evening with fairy lights")

# Save final result
for part in response.parts:
    if part.inline_data:
        part.as_image().save("coffee_shop_final.png")

Async Usage

import asyncio
from google import genai

client = genai.Client()

async def generate_variations(prompt: str, count: int = 4):
    """Generate multiple image variations concurrently."""
    tasks = [
        client.aio.models.generate_images(
            model="imagen-4.0-generate-001",
            prompt=prompt,
            config={"number_of_images": 1}
        )
        for _ in range(count)
    ]
    results = await asyncio.gather(*tasks)
    return [r.generated_images[0] for r in results]

Common Patterns

Logo Generation

prompt = """
A {style} logo for a {industry} company on a solid color background.
Include the text "{company_name}".
Style: minimalist, modern, clean lines
"""

Product Photography

prompt = """
Professional studio photo of {product},
{background} background,
{lighting} lighting,
4K, high detail, commercial quality
"""

Artistic Styles

Reference historical movements:

• "in the style of an impressionist painting"
• "in the style of pop art"
• "in the style of art deco poster"
• "digital art, trending on artstation"

Limitations

• Imagen: English prompts only, max 480 tokens
• Person generation: allow_all not available in EU, UK, CH, MENA
• Text rendering: Best under 25 characters
• Iterative editing: Only with Gemini native, not Imagen

Documentation Index

Syncing Documentation

cd skills/gemini-imagen
bun run scripts/sync-docs.ts