Merge pull request #143 from keflavich/header_nowcs

Strip the WCS out of the copied header
radio-astro-tools · Sep 10, 2014 · 75bb3e7 · 75bb3e7
2 parents 8e1b8fe + d7f1e1c
commit 75bb3e7
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Showing 3 changed files with 37 additions and 7 deletions.
diff --git a/spectral_cube/spectral_cube.py b/spectral_cube/spectral_cube.py
@@ -7,7 +7,7 @@
 
 from astropy import units as u
 from astropy.extern import six
-from astropy.io.fits import PrimaryHDU, ImageHDU, Header
+from astropy.io.fits import PrimaryHDU, ImageHDU, Header, Card
 from astropy import log
 from astropy import wcs
 
@@ -1514,7 +1514,8 @@ def to_yt(self, spectral_factor=1.0, nprocs=None, **kwargs):
 
         import yt
 
-        if StrictVersion(yt.__version__) >= StrictVersion('3.0'):
+        if ('dev' in yt.__version__ or
+            StrictVersion(yt.__version__) >= StrictVersion('3.0')):
 
             from yt.frontends.fits.api import FITSDataset
             from astropy.io import fits
@@ -1552,13 +1553,13 @@ def to_yt(self, spectral_factor=1.0, nprocs=None, **kwargs):
     @property
     def header(self):
         # Preserve non-WCS information from previous header iteration
-        header = self._header.copy()
+        header = wcs_utils.strip_wcs_from_header(self._header)
         header.update(self.wcs.to_header())
         header['BUNIT'] = self.unit.to_string(format='fits')
-        header['NAXIS'] = self._data.ndim
-        header['NAXIS1'] = self.shape[2]
-        header['NAXIS2'] = self.shape[1]
-        header['NAXIS3'] = self.shape[0]
+        header.insert(2, Card(keyword='NAXIS', value=self._data.ndim))
+        header.insert(3, Card(keyword='NAXIS1', value=self.shape[2]))
+        header.insert(4, Card(keyword='NAXIS2', value=self.shape[1]))
+        header.insert(5, Card(keyword='NAXIS3', value=self.shape[0]))
         # TODO: incorporate other relevant metadata here
         return header
 

diff --git a/spectral_cube/tests/test_spectral_cube.py b/spectral_cube/tests/test_spectral_cube.py
@@ -524,6 +524,7 @@ def test_header_naxis():
     assert cube.header['NAXIS1'] == data.shape[3]
     assert cube.header['NAXIS2'] == data.shape[2]
     assert cube.header['NAXIS3'] == data.shape[1]
+    assert 'NAXIS4' not in cube.header
 
 def test_slicing():
 

diff --git a/spectral_cube/wcs_utils.py b/spectral_cube/wcs_utils.py
@@ -301,3 +301,31 @@ def check_equality(wcs1, wcs2, warn_missing=False, ignore_keywords=['MJD-OBS',
                 OK = False
 
     return OK
+
+def strip_wcs_from_header(header):
+    """
+    Given a header with WCS information, remove ALL WCS information from that
+    header
+    """
+
+    hwcs = WCS(header)
+    wcsh = hwcs.to_header()
+
+    keys_to_keep = [k for k in header
+                    if (k and k not in wcsh and 'NAXIS' not in k)]
+
+    newheader = header.copy()
+    for kw in newheader.keys():
+        if kw not in keys_to_keep:
+            del newheader[kw]
+
+    for kw in ('CRPIX{ii}', 'CRVAL{ii}', 'CDELT{ii}', 'CUNIT{ii}',
+               'CTYPE{ii}', 'PC0{ii}_0{jj}', 'CD{ii}_{jj}',):
+        for ii in range(5):
+            for jj in range(5):
+                k = kw.format(ii=ii,jj=jj)
+                if k in newheader.keys():
+                    del newheader[k]
+
+
+    return newheader