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Add an option to use the corner of the pixel to compute the footprint #2348

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Merged
astrofrog merged 7 commits into from
Apr 23, 2014
Merged

Add an option to use the corner of the pixel to compute the footprint #2348

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061066a
Rename calcFootprint to calc_footprint. Add an optional boolean keywo…
nden Apr 21, 2014
409a073
fix docstrings
nden Apr 21, 2014
e3ffb56
rewrite calcFootprint to call calc_footprint
nden Apr 21, 2014
1cc3f3b
correct typo in docstrings
nden Apr 21, 2014
2b7f70d
add tests
nden Apr 22, 2014
7b093e0
added an entry in CHANGES
nden Apr 22, 2014
687a845
fix docstring
nden Apr 23, 2014
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5 changes: 5 additions & 0 deletions CHANGES.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -230,6 +230,11 @@ API Changes

- ``astropy.wcs``

- ``calcFootprint`` was deprecated. It is replaced by ``calc_footprint``.
An optional boolean keyword ``center`` was added to ``calc_footprint``.
It controls whether the centers or the corners of the pixels are used
in the computation. [#2384]

Bug Fixes
^^^^^^^^^

Expand Down
43 changes: 43 additions & 0 deletions astropy/wcs/tests/test_wcs.py
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Expand Up @@ -610,3 +610,46 @@ def test_out_of_bounds():

assert not np.isnan(ra)
assert not np.isnan(dec)


def test_calc_footprint_1():
fits = get_pkg_data_filename('data/sip.fits')
w = wcs.WCS(fits)

axes = (1000, 1051)
ref = np.array([[ 202.39314493, 47.17753352],
[ 202.71885939, 46.94630488],
[ 202.94631893, 47.15855022],
[ 202.72053428, 47.37893142]])
footprint = w.calc_footprint(axes=axes)
assert_allclose(footprint, ref)


def test_calc_footprint_2():
""" Test calc_footprint without distortion. """
fits = get_pkg_data_filename('data/sip.fits')
w = wcs.WCS(fits)

axes = (1000, 1051)
ref = np.array([[ 202.39265216, 47.17756518],
[ 202.7469062 , 46.91483312],
[ 203.11487481, 47.14359319],
[ 202.76092671, 47.40745948]])
footprint = w.calc_footprint(axes=axes, undistort=False)
assert_allclose(footprint, ref)


def test_calc_footprint_3():
""" Test calc_footprint with corner of the pixel."""
w = wcs.WCS()
w.wcs.ctype = ["GLON-CAR", "GLAT-CAR"]
w.wcs.crpix = [1.5, 5.5]
w.wcs.cdelt = [-0.1, 0.1]
axes = (2, 10)
ref = np.array([[0.1, -0.5],
[0.1, 0.5],
[359.9, 0.5],
[359.9, -0.5]])

footprint = w.calc_footprint(axes=axes, undistort=False, center=False)
assert_allclose(footprint, ref)
33 changes: 22 additions & 11 deletions astropy/wcs/wcs.py
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Expand Up @@ -548,7 +548,12 @@ def fix(self, translate_units='', naxis=None):
format(key, val),
FITSFixedWarning)

@deprecated("0.4", name="calcFootprint", alternative="calc_footprint")

@cdeil cdeil Apr 22, 2014

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This shows up like this in the HTML docs:

calcFootprint(*args, **kwargs)
Deprecated since version 0.4: Use calc_footprint instead.

Is this a bug or a feature of the @deprecated decorator that this doesn't show up like this?

def calcFootprint(self, header=None, undistort=True, axes=None)

@astrofrog astrofrog Apr 23, 2014

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Decorators don't easily preserve the call signature. If you want this to work we need to make use of the decorator.py package. Maybe you could open a new issue for this so we can discuss it? It might not be important since it's deprecated though - in fact, deprecated functions/methods should probably not show up in the API.

@cdeil cdeil Apr 23, 2014

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If it's not easy to do, I don't think it's worth the trouble.

@mdboom mdboom Apr 23, 2014

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There is a small bug in the @deprecated decorator (#2359), which unfortunately doesn't resolve this issue.

functools.wraps (which is the stdlib's simpler implementation of what decorator.py does) doesn't adapt the function signature of the wrapper. I don't know if this is worth adding yet another dependency.

@embray embray Apr 24, 2014

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I might open an issue for this actually. I don't think it's worth it for the @deprecated decorator itself, but I have been intended to write my own (similar to what decorator.py has) function to safely write new functions with a given call signature, for use with the modeling package. Once I have that it should be easy to make a wrapper around functools.wraps that includes this capability.

def calcFootprint(self, header=None, undistort=True, axes=None):
return self.calc_footprint(header=header, undistort=undistort, axes=axes,
center=True)

def calc_footprint(self, header=None, undistort=True, axes=None, center=True):

@cdeil cdeil Apr 22, 2014

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Can you change this:

header : astropy.io.fits header object, optional

to this:

header : `~astropy.io.fits.Header`, optional
    FITS Header

"""
Calculates the footprint of the image on the sky.

Expand All @@ -558,7 +563,7 @@ def calcFootprint(self, header=None, undistort=True, axes=None):

Parameters
----------
header : astropy.io.fits header object, optional
header : `~astropy.io.fits.Header` object, optional

undistort : bool, optional
If `True`, take SIP and distortion lookup table into
Expand All @@ -570,9 +575,13 @@ def calcFootprint(self, header=None, undistort=True, axes=None):
keywords from the header that was used to create this
`WCS` object.

center : bool, optional
If `True` use the center of the pixel, otherwise use the corner.

Returns
-------
coord : (4, 2) array of (*x*, *y*) coordinates.
The order is counter-clockwise starting with the bottom left corner.
"""
if axes is not None:
naxis1, naxis2 = axes
Expand All @@ -590,18 +599,20 @@ def calcFootprint(self, header=None, undistort=True, axes=None):
naxis1 = header.get('NAXIS1', None)
naxis2 = header.get('NAXIS2', None)

corners = np.zeros(shape=(4, 2), dtype=np.float64)
if naxis1 is None or naxis2 is None:
return None

corners[0, 0] = 1.
corners[0, 1] = 1.
corners[1, 0] = 1.
corners[1, 1] = naxis2
corners[2, 0] = naxis1
corners[2, 1] = naxis2
corners[3, 0] = naxis1
corners[3, 1] = 1.
if center == True:
corners = np.array([[1, 1],
[1, naxis2],
[naxis1, naxis2],
[naxis1, 1]], dtype = np.float64)
else:
corners = np.array([[0.5, 0.5],
[0.5, naxis2 + 0.5],
[naxis1 + 0.5, naxis2 + 0.5],
[naxis1 + 0.5, 0.5]], dtype = np.float64)

if undistort:
return self.all_pix2world(corners, 1)
else:
Expand Down Expand Up @@ -1721,7 +1732,7 @@ def footprint_to_file(self, filename=None, color='green', width=2):
f.write(comments)
f.write('linear\n')
f.write('polygon(')
self.calcFootprint().tofile(f, sep=',')
self.calc_footprint().tofile(f, sep=',')
f.write(') # color={0}, width={1:d} \n'.format(color, width))
f.close()

Expand Down