Set default BandInfo.band_{quantity,unit} to None (fixes #46).

When reading ENVI files, the band_quantity attribute of the SpyFile's BandInfo
object was being set to "Wavelength". While that is usually the case, it is
not always. Now, that assumption is no longer made and the  band_quantity and
band_unit attributes are defaulted to None in the BandInfo object (the previous
default was an empty string).

* graphics/spypylab.py:
  (plot): Handle band_quantity and band_unit default value None.
* io/envi.py:
  (open): band_quantity defaults to None instead of "Wavelength". If
    "wavelength units" is not specified in the header, default band_unit to
    None instead of empty string.
  (add_band_info_to_metadata): Handle and band_unit default value None.
* spectral.py:
  (BandInfo.__init__): Initialize band_quantity and band_unit to None.

Author: tboggs

spectral/graphics/spypylab.py

@@ -1301,9 +1301,15 @@ def plot(data, source=None):
     spectral._xyplot = p
     plt.grid(1)
     if source is not None and hasattr(source, 'bands'):
-        xlabel = source.bands.band_quantity
-        if len(source.bands.band_unit) > 0:
-            xlabel = xlabel + ' (' + source.bands.band_unit + ')'
+        if source.bands.band_quantity is not None:
+            xlabel = source.bands.band_quantity
+        else:
+            xlabel = ''
+        if source.bands.band_unit is not None:
+            if len(xlabel) > 0:
+                xlabel += ' (%s)' % source.bands.band_unit
+            else:
+                xlabel = str(source.bands.band_unit)
         plt.xlabel(xlabel)
     return p
 

spectral/io/envi.py

@@ -351,8 +351,7 @@ def open(file, image=None):
             img.bands.bandwidths = [float(f) for f in h['fwhm']]
         except:
             pass
-    img.bands.band_unit = h.get('wavelength units', "")
-    img.bands.band_quantity = "Wavelength"
+    img.bands.band_unit = h.get('wavelength units', None)
 
     return img
 
@@ -666,8 +665,8 @@ def add_band_info_to_metadata(bands, metadata, overwrite=False):
     if bands.bandwidths is not None and (overwrite is True or
                                       'fwhm' not in metadata):
         metadata['fwhm'] = bands.bandwidths
-    if len(bands.band_unit) > 0 and (overwrite is True or
-                                     'wavelength units' not in metadata):
+    if bands.band_unit is not None and (overwrite is True or
+                                        'wavelength units' not in metadata):
         metadata['wavelength units'] = bands.band_unit
 
 

spectral/spectral.py

@@ -221,8 +221,8 @@ def __init__(self):
         self.bandwidths = None
         self.centers_stdevs = None
         self.bandwidth_stdevs = None
-        self.band_quantity = ""
-        self.band_unit = ""
+        self.band_quantity = None
+        self.band_unit = None
 
 
 class Image(object):