def test_vs_sextractor():
"""Test behavior of sep versus sextractor.
Note: we turn deblending off for this test. This is because the
deblending algorithm uses a random number generator. Since the sequence
of random numbers is not the same between sextractor and sep or between
different platforms, object member pixels (and even the number of objects)
can differ when deblending is on.
Deblending is turned off by setting DEBLEND_MINCONT=1.0 in the sextractor
configuration file and by setting deblend_cont=1.0 in sep.extract().
"""
data = np.copy(image_data) # make an explicit copy so we can 'subfrom'
bkg = sep.Background(data, bw=64, bh=64, fw=3, fh=3)
# Test that SExtractor background is same as SEP:
bkgarr = bkg.back(dtype=np.float32)
assert_allclose(bkgarr, image_refback, rtol=1.e-5)
# Extract objects (use deblend_cont=1.0 to disable deblending).
bkg.subfrom(data)
objs = sep.extract(data, 1.5*bkg.globalrms, deblend_cont=1.0)
objs = np.sort(objs, order=['y'])
# Read SExtractor result
refobjs = np.loadtxt(IMAGECAT_FNAME, dtype=IMAGECAT_DTYPE)
refobjs = np.sort(refobjs, order=['y'])
# Found correct number of sources at the right locations?
assert_allclose(objs['x'], refobjs['x'] - 1., atol=1.e-3)
assert_allclose(objs['y'], refobjs['y'] - 1., atol=1.e-3)
# Test aperture flux
flux, fluxerr, flag = sep.sum_circle(data, objs['x'], objs['y'], 5.,
err=bkg.globalrms)
assert_allclose(flux, refobjs['flux_aper'], rtol=2.e-4)
assert_allclose(fluxerr, refobjs['fluxerr_aper'], rtol=1.0e-5)
# check if the flags work at all (comparison values
assert ((flag & sep.APER_TRUNC) != 0).sum() == 4
assert ((flag & sep.APER_HASMASKED) != 0).sum() == 0
# Test "flux_auto"
kr, flag = sep.kron_radius(data, objs['x'], objs['y'], objs['a'],
objs['b'], objs['theta'], 6.0)
flux, fluxerr, flag = sep.sum_ellipse(data, objs['x'], objs['y'],
objs['a'], objs['b'],
objs['theta'], r=2.5 * kr,
err=bkg.globalrms, subpix=1)
# For some reason, one object doesn't match. It's very small
# and kron_radius is set to 0.0 in SExtractor, but 0.08 in sep.
# Could be due to a change in SExtractor between v2.8.6 (used to
# generate "truth" catalog) and v2.18.11 (from which sep was forked).
i = 56 # index is 59 when deblending is on.
kr[i] = 0.0
flux[i] = 0.0
fluxerr[i] = 0.0
# We use atol for radius because it is reported to nearest 0.01 in
# reference objects.
assert_allclose(2.5*kr, refobjs['kron_radius'], atol=0.01, rtol=0.)
assert_allclose(flux, refobjs['flux_auto'], rtol=0.0005)
assert_allclose(fluxerr, refobjs['fluxerr_auto'], rtol=0.0005)
# Test ellipse representation conversion
cxx, cyy, cxy = sep.ellipse_coeffs(objs['a'], objs['b'], objs['theta'])
assert_allclose(cxx, objs['cxx'], rtol=1.e-4)
assert_allclose(cyy, objs['cyy'], rtol=1.e-4)
assert_allclose(cxy, objs['cxy'], rtol=1.e-4)
a, b, theta = sep.ellipse_axes(objs['cxx'], objs['cyy'], objs['cxy'])
assert_allclose(a, objs['a'], rtol=1.e-4)
assert_allclose(b, objs['b'], rtol=1.e-4)
assert_allclose(theta, objs['theta'], rtol=1.e-4)
#test round trip
cxx, cyy, cxy = sep.ellipse_coeffs(a, b, theta)
assert_allclose(cxx, objs['cxx'], rtol=1.e-4)
assert_allclose(cyy, objs['cyy'], rtol=1.e-4)
assert_allclose(cxy, objs['cxy'], rtol=1.e-4)
# test flux_radius
fr, flags = sep.flux_radius(data, objs['x'], objs['y'], 6.*refobjs['a'],
[0.1, 0.5, 0.6], normflux=refobjs['flux_auto'],
subpix=5)
assert_allclose(fr, refobjs["flux_radius"], rtol=0.04, atol=0.01)
# test winpos
sig = 2. / 2.35 * fr[:, 1] # flux_radius = 0.5
xwin, ywin, flag = sep.winpos(data, objs['x'], objs['y'], sig)
assert_allclose(xwin, refobjs["xwin"] - 1., rtol=0., atol=0.0025)
assert_allclose(ywin, refobjs["ywin"] - 1., rtol=0., atol=0.0025)
def test_vs_sextractor():
data = np.copy(image_data) # make an explicit copy so we can 'subfrom'
bkg = sep.Background(data, bw=64, bh=64, fw=3, fh=3)
# Test that SExtractor background is same as SEP:
bkgarr = bkg.back(dtype=np.float32)
assert_allclose(bkgarr, image_refback, rtol=1.e-5)
# Extract objects
bkg.subfrom(data)
objs = sep.extract(data, 1.5*bkg.globalrms)
objs = np.sort(objs, order=['y'])
# Read SExtractor result
refobjs = np.loadtxt(IMAGECAT_FNAME, dtype=IMAGECAT_DTYPE)
refobjs = np.sort(refobjs, order=['y'])
# Found correct number of sources at the right locations?
assert_allclose(objs['x'], refobjs['x'] - 1., atol=1.e-3)
assert_allclose(objs['y'], refobjs['y'] - 1., atol=1.e-3)
# Test aperture flux
flux, fluxerr, flag = sep.sum_circle(data, objs['x'], objs['y'], 5.,
err=bkg.globalrms)
assert_allclose(flux, refobjs['flux_aper'], rtol=2.e-4)
assert_allclose(fluxerr, refobjs['fluxerr_aper'], rtol=1.0e-5)
# check if the flags work at all (comparison values
assert ((flag & sep.APER_TRUNC) != 0).sum() == 4
assert ((flag & sep.APER_HASMASKED) != 0).sum() == 0
# Test "flux_auto"
kr, flag = sep.kron_radius(data, objs['x'], objs['y'], objs['a'],
objs['b'], objs['theta'], 6.0)
flux, fluxerr, flag = sep.sum_ellipse(data, objs['x'], objs['y'],
objs['a'], objs['b'],
objs['theta'], r=2.5 * kr,
err=bkg.globalrms, subpix=1)
# For some reason, object at index 59 doesn't match. It's very small
# and kron_radius is set to 0.0 in SExtractor, but 0.08 in sep.
# Most of the other values are within 1e-4 except one which is only
# within 0.01. This might be due to a change in SExtractor between
# v2.8.6 (used to generate "truth" catalog) and v2.18.11.
kr[59] = 0.0
flux[59] = 0.0
fluxerr[59] = 0.0
assert_allclose(2.5*kr, refobjs['kron_radius'], rtol=0.01)
assert_allclose(flux, refobjs['flux_auto'], rtol=0.01)
assert_allclose(fluxerr, refobjs['fluxerr_auto'], rtol=0.01)
# Test ellipse representation conversion
cxx, cyy, cxy = sep.ellipse_coeffs(objs['a'], objs['b'], objs['theta'])
assert_allclose(cxx, objs['cxx'], rtol=1.e-4)
assert_allclose(cyy, objs['cyy'], rtol=1.e-4)
assert_allclose(cxy, objs['cxy'], rtol=1.e-4)
a, b, theta = sep.ellipse_axes(objs['cxx'], objs['cyy'], objs['cxy'])
assert_allclose(a, objs['a'], rtol=1.e-4)
assert_allclose(b, objs['b'], rtol=1.e-4)
assert_allclose(theta, objs['theta'], rtol=1.e-4)
#test round trip
cxx, cyy, cxy = sep.ellipse_coeffs(a, b, theta)
assert_allclose(cxx, objs['cxx'], rtol=1.e-4)
assert_allclose(cyy, objs['cyy'], rtol=1.e-4)
assert_allclose(cxy, objs['cxy'], rtol=1.e-4)
# test flux_radius
fr, flags = sep.flux_radius(data, objs['x'], objs['y'], 6.*refobjs['a'],
[0.1, 0.5, 0.6], normflux=refobjs['flux_auto'],
subpix=5)
assert_allclose(fr, refobjs["flux_radius"], rtol=0.04, atol=0.01)
# test winpos
sig = 2. / 2.35 * fr[:, 1] # flux_radius = 0.5
xwin, ywin, flag = sep.winpos(data, objs['x'], objs['y'], sig)
assert_allclose(xwin, refobjs["xwin"] - 1., rtol=0., atol=0.0025)
assert_allclose(ywin, refobjs["ywin"] - 1., rtol=0., atol=0.0025)
