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fix WCS computation when importing fits

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This commit is contained in:
Thibault Barnouin
2025-04-10 18:14:38 +02:00
parent 3c321a7724
commit 278a31beab
2 changed files with 55 additions and 32 deletions
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42
package/lib/fits.py
View File

@@ -16,7 +16,7 @@ from astropy.io import fits
from astropy.wcs import WCS
from .convex_hull import clean_ROI
from .utils import wcs_PA
from .utils import wcs_CD_to_PC, wcs_PA
def get_obs_data(infiles, data_folder="", compute_flux=False):
@@ -61,26 +61,30 @@ def get_obs_data(infiles, data_folder="", compute_flux=False):
for i in range(len(data_array)):
data_array[i][data_array[i] < 0.0] = 0.0
# force WCS to convention PCi_ja unitary, cdelt in deg
# Compute CDELT, ORIENTAT from header
for wcs, header in zip(wcs_array, headers):
new_wcs = wcs.deepcopy()
if new_wcs.wcs.has_cd() or (new_wcs.wcs.cdelt[:2] == np.array([1.0, 1.0])).all():
# Update WCS with relevant information
if new_wcs.wcs.has_cd():
del new_wcs.wcs.cd
keys = list(new_wcs.to_header().keys()) + ["CD1_1", "CD1_2", "CD1_3", "CD2_1", "CD2_2", "CD2_3", "CD3_1", "CD3_2", "CD3_3"]
for key in keys:
header.remove(key, ignore_missing=True)
new_cdelt = np.linalg.eigvals(wcs.wcs.cd)
# new_cdelt.sort()
new_wcs.wcs.pc = wcs.wcs.cd.dot(np.diag(1.0 / new_cdelt))
new_wcs.wcs.cdelt = new_cdelt
for key, val in new_wcs.to_header().items():
header[key] = val
try:
header["ORIENTAT"] = float(header["ORIENTAT"])
except KeyError:
header["ORIENTAT"] = wcs_PA(new_wcs.wcs.pc[1, 0], np.diag(new_wcs.wcs.pc).mean())
if new_wcs.wcs.has_cd():
del new_wcs.wcs.cd
keys = list(new_wcs.to_header().keys()) + ["CD1_1", "CD1_2", "CD1_3", "CD2_1", "CD2_2", "CD2_3", "CD3_1", "CD3_2", "CD3_3"]
for key in keys:
header.remove(key, ignore_missing=True)
cdelt, orient = wcs_CD_to_PC(wcs.wcs.cd)
new_wcs.wcs.pc = wcs.wcs.cd.dot(np.diag(1.0 / cdelt))
new_wcs.wcs.cdelt = cdelt
try:
header["ORIENTAT"] = float(header["ORIENTAT"])
except KeyError:
header["ORIENTAT"] = -orient
elif new_wcs.wcs.has_pc() and (new_wcs.wcs.cdelt[:2] != np.array([1.0, 1.0])).all():
try:
header["ORIENTAT"] = float(header["ORIENTAT"])
except KeyError:
header["ORIENTAT"] = -wcs_PA(new_wcs.wcs.pc, new_wcs.wcs.cdelt)
else:
print("Could not compute ORIENTAT or CDELT from WCS")
for key, val in new_wcs.to_header().items():
header[key] = val
# force WCS for POL60 to have same pixel size as POL0 and POL120
is_pol60 = np.array([head["filtnam1"].lower() == "pol60" for head in headers], dtype=bool)

45
package/lib/utils.py
View File

@@ -154,27 +154,46 @@ def sci_not(v, err, rnd=1, out=str):
return *output[1:], -power
def wcs_PA(PC21, PC22):
def wcs_CD_to_PC(CD):
"""
Return the position angle in degrees to the North direction of a wcs
from the values of coefficient of its transformation matrix.
----------
Inputs:
PC21 : float
Value of the WCS matric PC[1,0]
PC22 : float
Value of the WCS matric PC[1,1]
CD : np.ndarray
Value of the WCS matrix CD
----------
Returns:
cdelt : (float, float)
Scaling factor in arcsec between pixel in X and Y directions.
orient : float
Angle in degrees between the North direction and the Up direction of the WCS.
"""
det = CD[0, 0] * CD[1, 1] - CD[0, 1] * CD[1, 0]
sgn = -1.0 if det < 0 else 1.0
cdelt = np.array([sgn, 1.0]) * np.sqrt(np.sum(CD**2, axis=1))
rot = np.arctan2(-CD[1, 0], sgn * CD[0, 0])
rot2 = np.arctan2(sgn * CD[0, 1], CD[1, 1])
orient = 0.5 * (rot + rot2) * 180.0 / np.pi
return cdelt, orient
def wcs_PA(PC, cdelt):
"""
Return the position angle in degrees to the North direction of a wcs
from the values of coefficient of its transformation matrix.
----------
Inputs:
PC : np.ndarray
Value of the WCS matrix PC
cdelt : (float, float)
Scaling factor in arcsec between pixel in X and Y directions.
----------
Returns:
orient : float
Angle in degrees between the North direction and the Up direction of the WCS.
"""
if (abs(PC21) > abs(PC22)) and (PC21 >= 0):
orient = -np.arccos(PC22) * 180.0 / np.pi
elif (abs(PC21) > abs(PC22)) and (PC21 < 0):
orient = np.arccos(PC22) * 180.0 / np.pi
elif (abs(PC21) < abs(PC22)) and (PC22 >= 0):
orient = np.arccos(PC22) * 180.0 / np.pi
elif (abs(PC21) < abs(PC22)) and (PC22 < 0):
orient = -np.arccos(PC22) * 180.0 / np.pi
rot = np.pi / 2.0 - np.arctan2(-cdelt[1] * PC[1, 0], abs(cdelt[0]) * PC[0, 0])
rot2 = np.pi / 2.0 - np.arctan2(abs(cdelt[0]) * PC[0, 1], cdelt[1] * PC[1, 1])
orient = 0.5 * (rot + rot2) * 180.0 / np.pi
return orient