This repository hosts the pretrained models for Galaxy Image Simplification using Generative AI, a pipeline that converts complex galaxy images into simplified, skeletonized representations suitable for quantitative morphology analysis.

The pipeline combines:

A ResNet-based classifier to select spiral galaxies
A conditional GAN (cGAN) to produce initial arm masks
A post-processing cGAN to smooth and connect broken arm segments

These models were trained on images from the DESI Legacy Survey with manually annotated spiral arms.

Model Sources

Code & full project:
https://github.com/SaiTeja-Erukude/galaxy-image-simplification-using-genai

Files in this repository

File name	Type	Description
`models/galaxy_classifier_resnet50.h5`	Keras model	ResNet-based binary classifier: spiral vs. non-spiral galaxy
`models/galaxy_simplifier_cgan.h5`	Keras model	Conditional GAN: galaxy RGB image ➜ initial arm-highlighted image
`models/postprocess_cgan.h5`	Keras model	Conditional GAN: initial mask ➜ refined, smooth/connected mask
`predict.py`	Python script	Full inference pipeline (classification ➜ simplifier cGAN ➜ post-cGAN)
`graphical_abstract.jpg`	Image	Graphical abstract / high-level overview of the Galaxy Simplifier pipeline
`requirements.txt`	Text file	Python dependencies needed for running inference
`README.md`	Markdown	Model card and usage instructions (this file)

Intended Use

What this model does

Given an optical galaxy image (RGB, 256×256):

ResNet classifier (galaxy_classifier_resnet50.h5)
- Predicts whether the galaxy is a spiral.
- Outputs a 2-class softmax:
  - class 0 – non-spiral / other
  - class 1 – spiral
- Typical usage: apply a confidence threshold on the spiral class (e.g. p_spiral > 0.65) before running the GAN pipeline.
Skeletonization cGAN (galaxy_simplifier_cgan.h5)
- Input: original RGB galaxy image (normalized to [-1, 1]).
- Output: image where white lines track the spiral arms (initial skeleton-like mask).
Post-processing cGAN (postprocess_cgan.h5)
- Input: initial cGAN output.
- Output: refined mask with smoother and better-connected arm structures.
- This can be further processed with classical image processing (thresholding, skeletonization, dilation) to produce final binary masks.

Primary use cases

Large-scale spiral galaxy selection and morphology analysis
Measuring arm geometry, pitch angles, and other structural properties
Building catalogs of simplified galaxy images from wide-field surveys

Not intended for

General-purpose image generation outside the astronomy domain
High-fidelity photometric modeling or pixel-perfect reconstruction of galaxies

How to use

You can either:

use your own inference script, or
use the provided minimalistic inference.py.

Citation

If you use this code, models, or catalog in your research, please cite:

bibtex

@article{erukude2025galaxy,
  title={Galaxy image simplification using Generative AI},
  author={Erukude, Sai Teja and Shamir, Lior},
  journal={Astronomy and Computing},
  pages={100990},
  year={2025},
  publisher={Elsevier}
}

erukude/galaxy-simplifier

Galaxy Image Simplification using Generative AI