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fix WCS computation when importing fits

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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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45
package/lib/utils.py
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@@ -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