def test_c_projections_shaped():
nx, ny = (5, 2)
x = np.linspace(0, 1, nx)
y = np.linspace(0, 1, ny)
xv, yv = np.meshgrid(x, y)
model = projections.Pix2Sky_TAN()
phi, theta = model(xv, yv)
assert_allclose(phi,
[[0., 90., 90., 90., 90.],
[180., 165.96375653, 153.43494882, 143.13010235, 135.]])
assert_allclose(
theta,
[[90., 89.75000159, 89.50001269, 89.25004283, 89.00010152],
[89.00010152, 88.96933478, 88.88210788, 88.75019826, 88.58607353]])
def convert_wcs(fitswcs):
'''
Accepts an astropy.wcs wcs object (based on the FITS standard).
Returns the GWCS equivalent WCS object.
'''
# this first version only handles non distorted ra,dec tangent projections
# check that it is that case
radesys_dict = {
'ICRS': coord.ICRS,
'FK5': coord.FK5,
'FK4': coord.FK4,
}
projection_dict = {
'TAN': projections.Pix2Sky_TAN(),
'SIN': projections.Pix2Sky_SIN()
}
fctypes = fitswcs.wcs.ctype
fcrval = fitswcs.wcs.crval
fcrpix = fitswcs.wcs.crpix
if fitswcs.naxis != 2:
raise ValueError("currently only handles 2d images")
print(fctypes)
ptypes = [ct[5:8] for ct in fctypes]
for ptype in ptypes:
print(ptype)
if ptype not in ['TAN', 'SIN']:
raise ValueError("currently only supports TAN and SIN projections")
tptype = ptype # temporary since this part is only for celestial coordinates
if fitswcs.cpdis1 or fitswcs.cpdis2: ### error here
raise ValueError("currently doesn't support distortion")
# Check for SIP correction
fsip = fitswcs.sip
if fsip:
sipa = Polynomial2D(fsip.a_order)
sipb = Polynomial2D(fsip.b_order)
assign_coefficients(sipa, fsip.a)
assign_coefficients(sipb, fsip.b)
# now the inverse, if it exists
if fsip.ap_order and fsip.bp_order:
sipap = Polynomial2D(fsip.ap_order)
sipbp = Polynomial2D(fsip.bp_order)
assign_coefficients(sipap, fsip.ap)
assign_coefficients(sipbp, fsip.bp)
else:
sipap = None
siptrans = Identity(2) + (Mapping((0, 1, 0, 1)) | (sipa & sipb))
if sipap:
siptrans.inverse = Identity(2) + (Mapping(
(0, 1, 0, 1)) | (sipap & sipbp))
# construct transformation
if fitswcs.wcs.has_cd():
trans1 = (Shift(-fcrpix[0]) & Shift(-fcrpix[1]))
trans2 = (projections.AffineTransformation2D(fitswcs.wcs.cd)
| projection_dict[tptype] | rotations.RotateNative2Celestial(
fcrval[0], fcrval[1], 180.))
elif fitswcs.wcs.has_pc():
trans1 = (Shift(-fcrpix[0]) & Shift(-fcrpix[1]))
pcmatrix = np.array(fitswcs.wcs.cdelt) * fitswcs.wcs.pc
trans2 = (projections.AffineTransformation2D(pcmatrix)
| projection_dict[tptype] | rotations.RotateNative2Celestial(
fcrval[0], fcrval[1], 180.))
else:
cdelt = fitswcs.wcs.cdelt
crota2 = fitswcs.wcs.crota[1] * np.pi / 180 # unware of any crota1 case
pscale_ratio = cdelt[1] / cdelt[0]
pcmatrix = np.array(
[[np.cos(crota2) * cdelt[0], -np.sin(crota2) * cdelt[1]],
[np.sin(crota2) * cdelt[0],
np.cos(crota2) * cdelt[1]]])
trans1 = (Shift(-fcrpix[0]) & Shift(-fcrpix[1]))
trans2 = (projections.AffineTransformation2D(pcmatrix)
| projection_dict[tptype] | rotations.RotateNative2Celestial(
fcrval[0], fcrval[1], 180.))
if fsip:
trans = trans1 | siptrans | trans2
else:
trans = trans1 | trans2
detector_frame = cf.Frame2D(name="detector",
axes_names=('x', 'y'),
unit=(u.pix, u.pix))
# Now see if a standard frame is referenced.
if fitswcs.wcs.radesys:
if fitswcs.wcs.radesys in radesys_dict:
reference_frame = radesys_dict[fitswcs.wcs.radesys]()
sky_frame = cf.CelestialFrame(reference_frame=reference_frame,
name=fitswcs.wcs.radesys.lower())
else:
sky_frame = '' # or None?
wcsobj = ggwcs.WCS(forward_transform=trans,
input_frame=detector_frame,
output_frame=sky_frame)
return wcsobj
