Remove flyback

python/stempy/io/__init__.py

@@ -259,16 +259,17 @@ def save_electron_counts(path, array):
     """
     array.write_to_hdf5(path)
 
-def load_electron_counts(path):
+def load_electron_counts(path, keep_flyback=True):
     """Load electron counted data from an HDF5 file.
 
     :param path: path to the HDF5 file.
     :type path: str
-
+    :param keep_flyback: option to crop the flyback column during loading
+    :type keep_flyback: bool
     :return: a SparseArray containing the electron counted data
     :rtype: SparseArray
     """
-    return SparseArray.from_hdf5(path)
+    return SparseArray.from_hdf5(path, keep_flyback=keep_flyback)
 
 def save_stem_images(outputFile, images, names):
     """Save STEM images to an HDF5 file.

python/stempy/io/sparse_array.py

@@ -170,11 +170,13 @@ def _validate(self):
                     raise Exception(msg)
 
     @classmethod
-    def from_hdf5(cls, filepath, **init_kwargs):
+    def from_hdf5(cls, filepath, keep_flyback=True, **init_kwargs):
         """Create a SparseArray from a stempy HDF5 file
 
         :param filepath: the path to the HDF5 file
         :type filepath: str
+        :param keep_flyback: option to crop the flyback column during loading
+        :type keep_flyback: bool
         :param init_kwargs: any kwargs to forward to SparseArray.__init__()
         :type init_kwargs: dict
 
@@ -188,19 +190,31 @@ def from_hdf5(cls, filepath, **init_kwargs):
 
             frames = f['electron_events/frames']
             scan_positions_group = f['electron_events/scan_positions']
-
-            data = frames[()]
             scan_shape = [scan_positions_group.attrs[x] for x in ['Nx', 'Ny']]
             frame_shape = [frames.attrs[x] for x in ['Nx', 'Ny']]
-
-            scan_positions = scan_positions_group[()]
+
+            if keep_flyback:
+                data = frames[()] # load the full data set
+                scan_positions = scan_positions_group[()]
+            else:
+                # Generate the original scan indices from the scan_shape
+                orig_indices = np.ravel_multi_index([ii.ravel() for ii in np.indices(scan_shape)],scan_shape)
+                # Remove the indices of the last column 
+                crop_indices = np.delete(orig_indices, orig_indices[scan_shape[0]-1::scan_shape[0]])
+                # Load only the data needed
+                data = frames[crop_indices]
+                # Reduce the column shape by 1
+                scan_shape[0] = scan_shape[0] - 1
+                # Create the proper scan_positions without the flyback column
+                scan_positions = np.ravel_multi_index([ii.ravel() for ii in np.indices(scan_shape)],scan_shape)
+
             # Load any metadata
             metadata = {}
             if 'metadata' in f:
                 load_h5_to_dict(f['metadata'], metadata)
 
         scan_shape = scan_shape[::-1]
-
+        
         if version >= 3:
             # Convert to int to avoid integer division that results in 
             # a float

tests/test_sparse_array.py

@@ -710,6 +710,12 @@ def compare_with_sparse(full, sparse):
     assert np.array_equal(m_array[[False, True], 0][0], position_one)
 
 
+def test_keep_flyback(electron_data_small):
+    flyback = SparseArray.from_hdf5(electron_data_small, keep_flyback=True)
+    assert flyback.scan_shape[1] == 50
+    no_flyback = SparseArray.from_hdf5(electron_data_small, keep_flyback=False)
+    assert no_flyback.scan_shape[1] == 49
+
 # Test binning until this number
 TEST_BINNING_UNTIL = 33