def test_wcs_affine_approximation():
wcs1 = WCS(naxis=2)
wcs1.wcs.ctype = 'DEC--TAN', 'RA---TAN'
wcs1.wcs.set()
data1 = Data(label='Data 1')
data1.coords = wcs1
data1['x'] = np.ones((2, 3))
wcs2 = WCS(naxis=2)
wcs2.wcs.ctype = 'DEC--TAN', 'RA---TAN'
wcs2.wcs.crpix = -3, 5
wcs2.wcs.cd = [[2, -1], [1, 2]]
wcs2.wcs.set()
data2 = Data(label='Data 2')
data2.coords = wcs2
data2['x'] = np.ones((2, 3))
link = WCSLink(data1, data2)
affine_link = link.as_affine_link(tolerance=0.1)
assert isinstance(affine_link, AffineLink)
assert_allclose(affine_link.matrix,
[[0.4, 0.2, -3.4], [-0.2, 0.4, 4.2], [0, 0, 1]],
atol=1e-5)
x1 = np.array([1.4, 3.2, 2.5])
y1 = np.array([0.2, 4.3, 2.2])
x2, y2 = link.forwards(x1, y1)
x3, y3 = affine_link.forwards(x1, y1)
assert_allclose(x2, x3, atol=1e-5)
assert_allclose(y2, y3, atol=1e-5)
x4, y4 = link.backwards(x1, y1)
x5, y5 = affine_link.backwards(x1, y1)
assert_allclose(x4, x5, atol=1e-5)
assert_allclose(y4, y4, atol=1e-5)
def test_wcs_offset_approximation():
wcs1 = WCS(naxis=2)
wcs1.wcs.ctype = 'DEC--TAN', 'RA---TAN'
wcs1.wcs.set()
data1 = Data(label='Data 1')
data1.coords = wcs1
data1['x'] = np.ones((2, 3))
wcs2 = WCS(naxis=2)
wcs2.wcs.ctype = 'DEC--TAN', 'RA---TAN'
wcs2.wcs.crpix = -3, 5
wcs2.wcs.set()
data2 = Data(label='Data 2')
data2.coords = wcs2
data2['x'] = np.ones((2, 3))
link = WCSLink(data1, data2)
offset_link = link.as_affine_link(tolerance=0.1)
assert isinstance(offset_link, OffsetLink)
assert_allclose(offset_link.offsets, [3, -5])
x1 = np.array([1.4, 3.2, 2.5])
y1 = np.array([0.2, 4.3, 2.2])
x2, y2 = link.forwards(x1, y1)
x3, y3 = offset_link.forwards(x1, y1)
assert_allclose(x2, x3, atol=1e-5)
assert_allclose(y2, y3, atol=1e-5)
x4, y4 = link.backwards(x1, y1)
x5, y5 = offset_link.backwards(x1, y1)
assert_allclose(x4, x5, atol=1e-5)
assert_allclose(y4, y4, atol=1e-5)