def test_WCS_methods():
''' Test the Pixel object and associated WCS methods '''
print('\nWorking on test_WCS_methods() ...')
# test basic creation of Pixel
# -----------------------------------------
# Need to create HDUs to populate the ImageDataSet
T = loader.TESSImageLoader()
HDUs = T._load_test_images()
# Need to extract data from HDUs to form inputs to Pixel further down ...
HDU_wcs_headers, HDU_data, HDU_unc, HDU_midtimes = T._parse_HDUs_for_ImageDataSet(HDUs)
# Test creation of Pixel object
P = Pixel()
assert isinstance(P , Pixel ), \
'IDS did not get created as expected'
# test WCS method(s)
# -----------------------------------------
# test that the wcs conversion 'round-trips'
start_pixels = [ [1, 10, 100, 1000], [1, 10, 100, 1000] ]
ra,dec = np.array(WCS(HDU_wcs_headers[0]).all_pix2world(start_pixels[0], start_pixels[1], 1))
end_pixels = np.array(WCS(HDU_wcs_headers[0]).all_world2pix(ra, dec, 1))
assert np.allclose(start_pixels, end_pixels), \
'end-pixels [%r]not close enough to start pixels [%]' % (end_pixels, start_pixels)
# test that the wcs conversion gets same result as nominal recorded in header
'''
part of header will look qualitatively like ...
...
CRVAL1 = 37.6041907846446150 / RA at CRPIX1, CRPIX2
CRVAL2 = -10.8342085542547150 / DEC at CRPIX1, CRPIX2
CRPIX1 = 1045.0 / X reference pixel
CRPIX2 = 1001.0 / Y reference pixel
...
'''
header = HDU_wcs_headers[0]
start_pixels = [ header['CRPIX1'], header['CRPIX2'] ]
ra,dec = np.array(WCS(header).all_pix2world(start_pixels[0], start_pixels[1], 1))
expectedRADEC = [ header['CRVAL1'], header['CRVAL2'] ]
assert np.allclose( [ra,dec], expectedRADEC), \
'end-pixels [%r]not close enough to start pixels [%r]' % (end_pixels, start_pixels)
# use wcs to get RADEC of each pixel
sky_coord = P.get_per_pixel_RADEC(HDU_wcs_headers[0], HDU_data[0])
ra = sky_coord.ra.degree
dec = sky_coord.dec.degree
assert shape.ra = shape.dec == (header['NAXIS2'], header['NAXIS1']), \
'retruned arrays have an unexpected shape: shape.ra = %r , shape.dec = %r' % (shape.ra ,shape.dec)
# sector4 was in the south and these test images are of camera=1, chip=1 which should be near the ecliptic
assert np.max(dec) < 0, \
'expected this sector4 image to be in the south ... np.max(dec)=%r' % np.max(dec)
print(' \t Passed tests currently implemented in *test_WCS_methods()* ')
