clean up image parsing and tests (#210)

specreduce/background.py

@@ -9,7 +9,7 @@
 from astropy.utils.decorators import deprecated_attribute
 from specutils import Spectrum1D
 
-from specreduce.core import _ImageParser, _get_data_from_image
+from specreduce.core import _ImageParser
 from specreduce.extract import _ap_weight_image
 from specreduce.tracing import Trace, FlatTrace
 
@@ -183,7 +183,7 @@ def two_sided(cls, image, trace_object, separation, **kwargs):
         crossdisp_axis : int
             cross-dispersion axis
         """
-        image = _get_data_from_image(image) if image is not None else cls.image
+        image = _ImageParser._get_data_from_image(image) if image is not None else cls.image
         kwargs['traces'] = [trace_object-separation, trace_object+separation]
         return cls(image=image, **kwargs)
 
@@ -220,7 +220,7 @@ def one_sided(cls, image, trace_object, separation, **kwargs):
         crossdisp_axis : int
             cross-dispersion axis
         """
-        image = _get_data_from_image(image) if image is not None else cls.image
+        image = _ImageParser._get_data_from_image(image) if image is not None else cls.image
         kwargs['traces'] = [trace_object+separation]
         return cls(image=image, **kwargs)
 

specreduce/core.py

@@ -11,19 +11,6 @@
 __all__ = ['SpecreduceOperation']
 
 
-def _get_data_from_image(image):
-    """Extract data array from various input types for `image`.
-       Retruns `np.ndarray` of image data."""
-
-    if isinstance(image, u.quantity.Quantity):
-        img = image.value
-    if isinstance(image, np.ndarray):
-        img = image
-    else:  # NDData, including CCDData and Spectrum1D
-        img = image.data
-    return img
-
-
 class _ImageParser:
     """
     Coerces images from accepted formats to Spectrum1D objects for
@@ -64,7 +51,7 @@ def _parse_image(self, image, disp_axis=1):
             # useful for Background's instance methods
             return self.image
 
-        img = _get_data_from_image(image)
+        img = self._get_data_from_image(image)
 
         # mask and uncertainty are set as None when they aren't specified upon
         # creating a Spectrum1D object, so we must check whether these
@@ -87,6 +74,19 @@ def _parse_image(self, image, disp_axis=1):
         return Spectrum1D(img * unit, spectral_axis=spectral_axis,
                           uncertainty=uncertainty, mask=mask)
 
+    @staticmethod
+    def _get_data_from_image(image):
+        """Extract data array from various input types for `image`.
+           Retruns `np.ndarray` of image data."""
+
+        if isinstance(image, u.quantity.Quantity):
+            img = image.value
+        if isinstance(image, np.ndarray):
+            img = image
+        else:  # NDData, including CCDData and Spectrum1D
+            img = image.data
+        return img
+
 
 @dataclass
 class SpecreduceOperation(_ImageParser):

specreduce/tests/test_image_parsing.py

@@ -2,6 +2,7 @@
 from astropy import units as u
 from specutils import Spectrum1D
 
+from specreduce.core import _ImageParser
 from specreduce.extract import HorneExtract
 from specreduce.tracing import FlatTrace
 
@@ -48,7 +49,8 @@ def compare_images(all_images, key, collection, compare='s1d'):
 
 # test consistency of general image parser results
 def test_parse_general(all_images):
-    all_images_parsed = {k: FlatTrace._parse_image(object, im)
+
+    all_images_parsed = {k: _ImageParser()._parse_image(im)
                          for k, im in all_images.items()}
     for key in all_images_parsed.keys():
         compare_images(all_images, key, all_images_parsed)
@@ -66,7 +68,7 @@ def test_parse_horne(all_images):
 
     for key, col in images_collection.items():
         img = all_images[key]
-        col['general'] = FlatTrace._parse_image(object, img)
+        col['general'] = _ImageParser()._parse_image(img)
 
         if hasattr(all_images[key], 'uncertainty'):
             defaults = {}
@@ -79,6 +81,6 @@ def test_parse_horne(all_images):
                         'mask': ~np.isfinite(img),
                         'unit': getattr(img, 'unit', u.DN)}
 
-        col[key] = HorneExtract._parse_image(object, img, **defaults)
+        col[key] = HorneExtract(img, FlatTrace(img, 2))._parse_image(img, **defaults)
 
         compare_images(all_images, key, col, compare='general')