image-generation

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Translated

Guide to image generation and editing in MassGen. Use when creating images, editing existing images, iterating on image designs, or choosing between image backends (OpenAI, Google Gemini/Imagen, Grok, OpenRouter).

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NPX Install

npx skill4agent add massgen/massgen image-generation

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Translated version includes tags in frontmatter
image-generationai-artmassgentext-to-imageimage-editing

SKILL.md Content

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Image Generation

Generate images using 
generate_media
with 
mode="image"
. The system auto-selects the best backend based on available API keys.

Quick Start

python
# Simple text-to-image (auto-selects backend)
generate_media(prompt="A cat in space", mode="image")

# Specify backend and quality
generate_media(prompt="A logo for a coffee shop", mode="image",
               backend_type="openai", quality="high")

# Batch generation (parallel)
generate_media(prompts=["sunset over ocean", "mountain landscape", "city at night"],
               mode="image", max_concurrent=3)

Backend Comparison

BackendDefault ModelStrengthsAPI Key
Google (priority 1)
gemini-3.1-flash-image-preview
(Nano Banana 2)		Fast, flexible sizes, image editing, multi-turn
GOOGLE_API_KEY
or 
GEMINI_API_KEY
OpenAI (priority 2)
gpt-5.4
High quality, transparent backgrounds, continuation via response ID
OPENAI_API_KEY
Grok (priority 3)
grok-imagine-image
1k resolution, continuation via stored data URI
XAI_API_KEY
OpenRouter (priority 4)
google/gemini-3.1-flash-image-preview
Access to multiple models via single API
OPENROUTER_API_KEY

Key Parameters

ParameterDescriptionExample
prompt
Text description of the image
"A watercolor painting of mountains"
backend_type
Force a specific backend
"google"
, 
"openai"
, 
"grok"
, 
"openrouter"
model
Override default model
"gemini-3-pro-image-preview"
for studio quality
quality
Image quality (OpenAI)
"low"
, 
"medium"
, 
"high"
, 
"auto"
size
Image dimensionsSee backends reference
aspect_ratio
Aspect ratio
"16:9"
, 
"1:1"
, 
"4:5"
input_images
Source images for image-to-image editing
["photo.jpg"]
continue_from
Continuation ID for multi-turn editing
result["continuation_id"]

Image-to-Image Editing

Transform existing images by providing 
input_images
:
python
generate_media(
    prompt="Make it look like a watercolor painting",
    mode="image",
    input_images=["photo.jpg"]
)
Supported backends for image-to-image: Google (Gemini), OpenAI, Grok. The system auto-selects if your current backend doesn't support it.

Multi-Turn Editing (Continuation)

Iteratively refine images using 
continue_from
:
python
# First generation
result = generate_media(prompt="A logo for a coffee shop", mode="image")

# Refine using the continuation ID
result2 = generate_media(
    prompt="Make the text larger and add a cup icon",
    mode="image",
    continue_from=result["continuation_id"]
)
Each backend uses a different continuation mechanism:
  • OpenAI: Passes 
    previous_response_id
    (stateless)
  • Google Gemini: In-memory chat store (LRU, 50 items)
  • Grok: In-memory data URI store (LRU, 50 items)
Continuation only works for single image generation (not batch).

Google: Gemini vs Imagen

Google supports two API paths. Gemini (Nano Banana 2) is the default and recommended for most use cases. Imagen is only needed for advanced reference-image editing features.
  • Gemini models (
    gemini-*
    ): 
    generate_content()
    — text-to-image, image editing via 
    input_images
    , multi-turn continuation
  • Imagen models (
    imagen-*
    ): 
    generate_images()
    / 
    edit_image()
    — text-to-image with 
    negative_prompt
    /
    seed
    /
    guidance_scale
    , plus style transfer, control editing, and subject consistency via reference images
For studio-quality precision and text rendering, use: 
model="gemini-3-pro-image-preview"
(Pro-tier).

Need More Control?

  • Per-backend sizes, quality options, and quirks: See references/backends.md
  • Complete 
    extra_params
    reference    : See references/extra_params.md
  • Advanced editing (inpainting, style transfer, control, subject): See references/editing.md