SR-GAN

HF Repo to go along with https://github.com/simon-donike/SISR-RS-SRGAN

<img src="https://github.com/ESAOpenSR/opensr-model/blob/main/resources/opensr_logo.png?raw=true" width="250"/>

🌍 Single Image Super-Resolution Remote Sensing 'SRGAN'

Description: Remote-Sensing-SRGAN is a flexible, research‑grade GAN framework for super‑resolution (SR) of Sentinel‑2 and other remote‑sensing imagery. It supports arbitrary input band counts, configurable architectures, scalable depth/width, and a modular loss system—with a robust training strategy (generator pretraining, adversarial ramp‑up, and discriminator schedules) that stabilizes traditionally sensitive GAN training on EO data.

---

📖 Documentation

New: Documentation!

🧠 Overview

This repository provides:

• Training code for SRGAN‑style models tailored to remote sensing.
• A flexible generator and discriminator with multiple block implementations and pluggable depths/widths.
• Configurable losses (content/perceptual/adversarial) with fully exposed loss weights.
• A stabilized GAN procedure (G‑only pretraining → adversarial ramp‑up → scheduled D , EMA weights) that makes RS‑SR training more reliable.
• Smooth integration with the OpenSR ecosystem for data handling, evaluation, and large‑scene inference.
• Configuration‑first workflow: everything — from generator/discriminator choices to loss weights and warmup length — is selectable in configs/config.yaml.

Key Features

• 🧩 Flexible generator: choose block type res, rcab, rrdb, or lka; set n_blocks, n_channels, and scale ∈ {2,4,8}.
• 🛰️ Flexible inputs: train on any band layout (e.g., S2 RGB‑NIR, 6‑band stacks, or custom multispectral sets). Normalization/denorm utilities provided.
• ⚖️ Flexible losses & weights: combine L1, Spectral Angle Mapper, VGG19 or LPIPS perceptual distances, Total Variation, and a BCE adversarial term with per‑loss weights.
• 🧪 Robust training strategy: generator pretraining, linear adversarial loss ramp, cosine/linear LR warmup, and discriminator update schedules/curves.
• ⚡ Multi-GPU acceleration: run Lightning's DDP backend out of the box by listing multiple GPU IDs in Training.gpus for dramatically faster epochs on capable machines.
• 🌀 Generator EMA tracking: optional exponential moving average weights for sharper validation and inference results.
• 📊 Clear monitoring: PSNR, SSIM, LPIPS, qualitative panels, and Weights & Biases logging.

---

🧱 Architectures & Blocks (short)

• SRResNet (res): Residual blocks without BN, residual scaling; strong content backbone for pretraining.
• RCAB (rcab): Residual Channel Attention Blocks (attention via channel‑wise reweighting) for enhanced detail contrast in textures.
• RRDB (rrdb): Residual‑in‑Residual Dense Blocks (as in ESRGAN); deeper receptive fields with dense skip pathways for sharper detail.
• LKA (lka): Large‑Kernel Attention blocks approximating wide‑context kernels; good for large structures common in RS (fields, roads, shorelines).

⚙️ Config‑driven components

The YAML keeps the SRGAN flexible: swap architectures or rebalance perceptual vs. spectral fidelity without touching the code.

---

🧰 Installation

Option 1 — install the packaged model (recommended for inference)

The project can be consumed directly from PyPI:

python -m pip install opensr-srgan

After installation you have two options for model creation:

1. Instantiate directly from a config + weights when you manage checkpoints yourself.

   from opensr_srgan import load_from_config
   
   model = load_from_config(
       config_path="configs/config_10m.yaml",
       checkpoint_uri="https://example.com/checkpoints/srgan.ckpt",
       map_location="cpu",  # optional
   )
   

2. Load the packaged inference presets (either "RGB-NIR" or "SWIR").

   The helper fetches the appropriate configuration (e.g., config_RGB-NIR.yaml) and pretrained checkpoint (e.g., RGB-NIR_4band_inference.ckpt) from the simon-donike/SR-GAN repository on the Hugging Face Hub and caches them locally for reuse.

   from opensr_srgan import load_inference_model
   
   rgb_model = load_inference_model("RGB-NIR", map_location="cpu")
   swir_model = load_inference_model("SWIR")
   

Both helpers return a ready-to-use pytorch_lightning.LightningModule; access its .generator attribute for inference-ready PyTorch modules.

Option 2 — work from source

⚠️ Python version: the pinned torch==1.13.1 and torchvision==0.14.1 wheels target Python 3.10 (or earlier). Create your environment with a Python 3.10 interpreter to avoid installation failures on newer runtimes (e.g., Python 3.11).

# Clone the repository
git clone https://github.com/ESAOpenSR/Remote-Sensing-SRGAN.git
cd Remote-Sensing-SRGAN

# (optional) Create a Python 3.10 virtual environment
python3.10 -m venv .venv
source .venv/bin/activate

# (recommended) Upgrade pip so dependency resolution succeeds
python -m pip install --upgrade pip

# Install project dependencies
pip install -r requirements.txt

# (optional) Install extras for LPIPS metrics or TacoReader data loading
# pip install lpips tacoreader

ℹ️ Tip: If the default PyPI index cannot find torch==1.13.1, install PyTorch directly from the official wheel index before running pip install -r requirements.txt:

# CUDA 11.7 builds
pip install torch==1.13.1 torchvision==0.14.1 --index-url https://download.pytorch.org/whl/cu117

---

🚀 Quickstart

0) Data

Make sure the datafolders exist and are correctly associated with the dataset classes in the dataset folder. Use either your own data or any of the provided datasets in the data/ folder.

1) SRGAN Training

Train the GAN model.

python train.py --config configs/config.yaml

Multi-GPU training is enabled by setting Training.gpus in your config to a list of device indices (e.g. [0, 1, 2, 3]). The trainer automatically switches to Distributed Data Parallel (DDP), yielding significantly faster wall-clock times when scaling out across multiple GPUs.

2) Inference on Large Scenes

Use OpenSR‑Utils for tiled processing of SAFE/S2GM/GeoTIFF inputs.

import opensr_utils
from opensr_utils.model_utils import get_srgan

model = get_srgan(weights="path/to/checkpoint.ckpt")
opensr_utils.large_file_processing(
    root="/path/to/S2_or_scene",
    model=model,
    output_dir="/path/to/output"
)

---

🏗️ Configuration Highlights

All key knobs are exposed via YAML in the configs folder:

• Model: in_channels, n_channels, n_blocks, scale, block_type ∈ {SRResNet, res, rcab, rrdb, lka}
• Losses: l1_weight, sam_weight, perceptual_weight, tv_weight, adv_loss_beta
• Training: pretrain_g_only, g_pretrain_steps, adv_loss_ramp_steps, label_smoothing, generator LR warmup (Schedulers.g_warmup_steps, Schedulers.g_warmup_type), discriminator cadence controls
• Data: band order, normalization stats, crop sizes, augmentations

---

🎚️ Training Stabilization Strategies

• G‑only pretraining: Train with content/perceptual losses while the adversarial term is held at zero during the first g_pretrain_steps.
• Adversarial ramp‑up: Increase the BCE adversarial weight linearly or smoothly (cosine) over adv_loss_ramp_steps until it reaches adv_loss_beta.
• Generator LR warmup: Ramp the generator optimiser with a cosine or linear schedule for the first 1–5k steps via Schedulers.g_warmup_steps/g_warmup_type before switching to plateau-based reductions.
• EMA smoothing: Enable Training.EMA.enabled to keep a shadow copy of the generator. Decay values in the 0.995–0.9999 range balance responsiveness with stability and are swapped in automatically for validation/inference.

The schedule and ramp make training easier, safer, and more reproducible.

---

🧪 Validation & Logging

• Metrics: PSNR, SSIM, LPIPS (PSNR/SSIM use sen2_stretch with clipping for stable reflectance ranges)
• Visuals: side‑by‑side LR/SR/HR panels (clamped, stretched), saved under visualizations/
• W&B: loss curves, example previews, system metrics
• Outputs: all logs, configs, and artifacts are centralized in logs/ and on WandB.

---

🛰️ Datasets

Two dataset pipelines ship with the repository under data/. Both return (lr, hr) pairs that are wired into the training LightningDataModule through data/data_utils.py.

Sentinel‑2 SAFE windowed chips

• Purpose. Allows training directly from raw Sentinel‑2 Level‑1C/Level‑2A .SAFE products. A manifest builder enumerates the granule imagery, records chip windows, and the dataset turns each window into an (lr, hr) pair.
• Pipeline.
  1. S2SAFEWindowIndexBuilder crawls a root directory of .SAFE products, collects the band metadata, and (optionally) windows each raster into fixed chip sizes, storing the results as JSON.
  2. S2SAFEDataset groups those single‑band windows by granule, stacks the requested band order, and crops everything to the requested high‑resolution size (default 512×512).
  3. The stacked HR tensor is downsampled in code with anti‑aliased bilinear interpolation to create the LR observation, so the model sees the interpolated image as input and the original Sentinel‑2 patch as target. Invalid chips (NaNs, nodata, near‑black) are filtered out during training.
• Setup.
  1. Organise your .SAFE products under a common root (the builder expects the usual GRANULE/<id>/IMG_DATA structure).
  2. Run the builder (see the __main__ example in data/SEN2_SAFE/S2_6b_ds.py) to generate a manifest JSON containing file metadata and chip coordinates.
  3. Instantiate S2SAFEDataset with the manifest path, the band list/order, your desired hr_size, and the super‑resolution factor. The dataset will normalise values and synthesise the LR input automatically.

SEN2NAIP (4× Sentinel‑2 → NAIP pairs)

• Purpose. Wraps the Taco Foundation SEN2NAIPv2 release, which provides pre‑aligned Sentinel‑2 observations and NAIP aerial reference chips. The dataset class simply reads the file paths stored in the .taco manifest and loads the rasters on the fly—Sentinel‑2 frames act as the low‑resolution input, NAIP tiles are the 4× higher‑resolution target.
• Scale. This loader is hard‑coded for 4× super‑resolution. The Taco manifest already contains the bilinearly downsampled Sentinel‑2 inputs, so no alternative scale factors are exposed.
• Setup.
  1. Install the optional dependencies used by the loader: pip install tacoreader rasterio (plus Git LFS for the download step).
  2. Fetch the dataset by running python data/SEN2AIP/download_S2N.py. The helper script downloads the manifest and image tiles from the Hugging Face hub into the working directory.
  3. Point your config to the resulting .taco file when you instantiate SEN2NAIP (e.g. in a custom select_dataset branch). No extra preprocessing is required—the dataset returns NumPy arrays that are subsequently converted to tensors by the training pipeline.

Adding a new dataset

1. Create the dataset class inside data/<your_dataset>/. Mirror the existing API (__len__, __getitem__ returning (lr, hr)) so it can plug into the shared training utilities.
2. Register it with the selector by adding a new branch in data/data_utils.py::select_dataset, alongside the existing S2_6b/S2_4b options, so the configuration key resolves to your implementation.
3. Expose a config toggle by adding the new Data.dataset_type value to your experiment YAML (for example configs/config_20m.yaml). Point any dataset‑specific parameters (paths, band lists, scale factors) to your new loader inside that branch.

This keeps dataset plumbing centralised: dataset classes own their I/O logic, select_dataset wires them into Lightning, and the configuration file becomes the single switch for experiments.

---

📂 Repository Structure

Remote-Sensing-SRGAN/
├── models/                # Generator/Discriminator + block implementations
├── utils/                 # Normalization, stretching, plotting, logging
├── utils/                 # Dataset implementations and downloading scripts
├── train.py               # Training entry point (Lightning-compatible)

---

📚 Related Projects

• OpenSR‑Model – Latent Diffusion SR (LDSR‑S2)
• OpenSR‑Utils – Large‑scale inference & data plumbing
• OpenSR‑Test – Benchmarks & metrics
• SEN2NEON – Multispectral HR reference dataset

---

✍️ Citation

If you use this work, please cite:

coming soon...

---

🧑‍🚀 Authors & Acknowledgements

Developed by Simon Donike (IPL–UV) within the ESA Φ‑lab / OpenSR initiative.

📒 Notes

This repo has been extensively reworked using Codex since I wanted to see if/how well it works. The AI changes were mostly about structuring, commenting, documentation, and small-scale features. The GAN workflow itself was adapted from my previous implementations and the resulting experience with training these models: (Remote-Sensing-SRGAN) and NIR-GAN.
Only the SEN2 dataset class has been generated from scratch and can be considered AI slop. But since it works, I wont touch it again.

🧑‍🚀 ToDOs

• create inference.py (interface with opensr-test)
• build interface with SEN2SR (for 10m + 20m SR)
• incorporate the SEN2NAIP versions + downloading
• implement different discriminators
• implement different visual loses (like LPIPS, VGG, ...)
• upgrade to torch>2.0 (complicated, PL doesnt support multiple schedulers in >2)