utils/create_splits.py

import os
import random
from glob import glob
import json
from huggingface_hub import hf_hub_download
from tqdm import tqdm
import numpy as np

from astropy.io import fits
from astropy.wcs import WCS
import datasets
from datasets import DownloadManager
from fsspec.core import url_to_fs

def get_fits_footprint(fits_path):
    """
    Process a FITS file to extract WCS information and calculate the footprint.

    Parameters:
    fits_path (str): Path to the FITS file.

    Returns:
    tuple: A tuple containing the WCS footprint coordinates.
    """
    with fits.open(fits_path) as hdul:
        wcs = WCS(hdul[1].header)
        shape = sorted(tuple(wcs.pixel_shape))[:2]
        footprint = wcs.calc_footprint(axes=shape)
        coords1 = list(footprint.flatten())
        
        wcs = WCS(hdul[4].header)
        shape = sorted(tuple(wcs.pixel_shape))[:2]
        footprint = wcs.calc_footprint(axes=shape)
        coords2 = list(footprint.flatten())
        
    return coords1, coords2


def calculate_pixel_scale(header):
    """
    Calculate the pixel scale separately for X and Y directions and return the mean pixel scale from a FITS header.
    
    Args:
    header: A FITS header object containing CD1_1, CD1_2, CD2_1, and CD2_2.
    
    Returns:
    mean_pixscale: The mean pixel scale in arcseconds per pixel.
    """
    # Extract CD matrix elements
    CD1_1 = header['CD1_1']
    CD1_2 = header['CD1_2']
    CD2_1 = header['CD2_1']
    CD2_2 = header['CD2_2']
    
    # Calculate pixel scales
    pixscale_x = (CD1_1**2 + CD1_2**2)**0.5 * 3600  # Convert from degrees to arcseconds
    pixscale_y = (CD2_1**2 + CD2_2**2)**0.5 * 3600  # Convert from degrees to arcseconds
    
    # Calculate mean pixel scale
    mean_pixscale = (pixscale_x + pixscale_y) / 2
    
    return mean_pixscale


def make_split_jsonl_files(
    config_type="tiny", data_dir="./data", outdir="./splits", seed=42
):
    """
    Create jsonl files for the SBI-16-2D dataset.

    config_type: str, default="tiny"
        The type of split to create. Options are "tiny" and "full".
    data_dir: str, default="./data"
        The directory where the FITS files are located.
    outdir: str, default="./splits"
        The directory where the jsonl files will be created.
    seed: int, default=42
        The seed for the random split.
    """
    random.seed(seed)
    os.makedirs(outdir, exist_ok=True)

    fits_files = glob(os.path.join(data_dir, "*.fits"))
    random.shuffle(fits_files)
    if config_type == "tiny":
        train_files = fits_files[:2]
        test_files = fits_files[2:3]
    elif config_type == "full":
        split_idx = int(0.8 * len(fits_files))
        train_files = fits_files[:split_idx]
        test_files = fits_files[split_idx:]
    else:
        raise ValueError("Unsupported config_type. Use 'tiny' or 'full'.")

    def create_jsonl(files, split_name):
        output_file = os.path.join(outdir, f"{config_type}_{split_name}.jsonl")
        with open(output_file, "w") as out_f:
            for file in tqdm(files):
                #print(file, flush=True, end="...")
                with fits.open(file, memmap=False) as hdul:
                    image_id = os.path.basename(file).split(".fits")[0]
                    ra = hdul["SCI"].header.get("CRVAL1", 0)
                    dec = hdul["SCI"].header.get("CRVAL2", 0)
                    exptime = hdul[0].header.get("EXPTIME", -1)
                    pixscale = calculate_pixel_scale(hdul[1].header)
                    footprint = get_fits_footprint(file)
                    item = {
                        "image_id": image_id,
                        "image": file,
                        "ra": ra,
                        "dec": dec,
                        "pixscale": pixscale,
                        "exposure_time": exptime,
                        "footprint": footprint,
                    }
                    out_f.write(json.dumps(item) + "\n")

    create_jsonl(train_files, "train")
    create_jsonl(test_files, "test")

if __name__ == "__main__":
    make_split_jsonl_files("tiny")
    make_split_jsonl_files("full")