def get_arc_conv(w: wcs.WCS):
""" Gets pixels to arc-seconds conversion scale (Number of arcseconds per pixel) """
pix_x, pix_y = 1, 1
ra_1, dec_1 = w.wcs_pix2world(pix_x, pix_y, 0)
ra_2, dec_2 = w.wcs_pix2world(pix_x + 1, pix_y + 1, 0)
diff_1 = abs(ra_1 - ra_2) * 3600
diff_2 = abs(dec_1 - dec_2) * 3600
return (diff_1 + diff_2) / 2
def wcsTest():
wcsPath = getResourcePath('ISS030-E-102170_dc.wcs')
header = readHeader(wcsPath)
# the pixel coordinates of which we want the world coordinates
x, y = np.meshgrid(np.arange(0,4000), np.arange(0,2000))
x = x.ravel()
y = y.ravel()
# first, calculate using astropy as reference
wcs = WCS(header)
t0 = time.time()
ra_astropy, dec_astropy = wcs.wcs_pix2world(x, y, 0)
print('astropy wcs:', time.time()-t0, 's')
# now, check against our own implementation
#tan_pix2world(header, x, y, 0) # warmup
t0 = time.time()
ra, dec = tan_pix2world(header, x, y, 0)
print('own wcs:', time.time()-t0, 's')
assert_almost_equal([ra, dec], [ra_astropy, dec_astropy])