add compute_ra_dec_range

csst_dfs_commons/utils/fits.py

@@ -3,6 +3,7 @@ from astropy.coordinates import ICRS
 from astropy import units as u
 from astropy.coordinates import SkyCoord
 from astropy.io import fits
+from astropy import wcs
 
 from csst_dfs_commons.models.constants import PI, DEFAULT_NSIDE
 
@@ -110,3 +111,27 @@ def dfs_heapix_sql_condition(ra, dec, radius, ra_col = 'ra', dec_col = 'dec', br
     whereSql = f"{distance} <= 4*pow(pi()*{radius}/180.0/2, 2) and {whereZoneSql}"
 
     return whereSql
+
+def compute_ra_dec_range(hdulist):
+    header = hdulist[1].header
+    fits_wcs = wcs.WCS(header)
+
+    # Get the shape of the data
+    naxis1 = header['NAXIS1']
+    naxis2 = header['NAXIS2']
+
+    # Get the pixel coordinates of all corners
+    corners = [(0, 0), (naxis1, 0), (naxis1, naxis2), (0, naxis2)]
+
+    # Convert pixel coordinates of corners to RA and Dec
+    corners_coords = fits_wcs.all_pix2world(corners, 0)
+
+    # Extract RA and Dec values
+    ras = [coord[0] for coord in corners_coords]
+    decs = [coord[1] for coord in corners_coords]
+
+    # Compute the min and max of RA and Dec
+    min_ra, max_ra = min(ras), max(ras)
+    min_dec, max_dec = min(decs), max(decs)
+
+    return min_ra, max_ra, min_dec, max_dec