Merge pull request #127 from kecnry/bg-oob-checks

logic to detect background regions extending beyond image limits

Author: kecnry

CHANGES.rst

@@ -1,6 +1,15 @@
-1.1.0 (unreleased)
+1.2.0 (unreleased)
 ------------------
 
+Bug Fixes
+^^^^^^^^^
+
+- Improved errors/warnings when background region extends beyond bounds of image. [#127]
+
+
+1.1.0
+-----
+
 New Features
 ^^^^^^^^^^^^
 

specreduce/background.py

@@ -1,5 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 
+import warnings
 from dataclasses import dataclass, field
 
 import numpy as np
@@ -87,6 +88,13 @@ def _to_trace(trace):
         bkg_wimage = np.zeros_like(self.image, dtype=np.float64)
         for trace in self.traces:
             trace = _to_trace(trace)
+            if (np.any(trace.trace.data >= self.image.shape[self.crossdisp_axis]) or
+                    np.any(trace.trace.data < 0)):
+                raise ValueError("center of background window goes beyond image boundaries")
+            elif (np.any(trace.trace.data + self.width/2. >= self.image.shape[self.crossdisp_axis])
+                  or np.any(trace.trace.data - self.width/2. < 0)):
+                warnings.warn("background window extends beyond image boundaries")
+            # pass trace.trace.data to ignore any mask on the trace
             bkg_wimage += _ap_weight_image(trace,
                                            self.width,
                                            self.disp_axis,

specreduce/extract.py

@@ -71,7 +71,8 @@ def _ap_weight_image(trace, width, disp_axis, crossdisp_axis, image_shape):
     # loop in dispersion direction and compute weights.
     for i in range(image_shape[disp_axis]):
         # TODO trace must handle transposed data (disp_axis == 0)
-        wimage[:, i] = _get_boxcar_weights(trace[i], hwidth, image_sizes)
+        # pass trace.trace.data[i] to avoid any mask if part of the regions is out-of-bounds
+        wimage[:, i] = _get_boxcar_weights(trace.trace.data[i], hwidth, image_sizes)
 
     return wimage
 

specreduce/tests/test_background.py

@@ -1,3 +1,4 @@
+import pytest
 import numpy as np
 
 import astropy.units as u
@@ -42,3 +43,13 @@ def test_background():
     sub3 = bg1.sub_image()
     assert np.allclose(sub1, sub2)
     assert np.allclose(sub1, sub3)
+
+
+def test_oob():
+    # image.shape (30, 10)
+    with pytest.warns(match="background window extends beyond image boundaries"):
+        Background.two_sided(image, 25, 4, width=3)
+
+    with pytest.raises(ValueError,
+                       match="center of background window goes beyond image boundaries"):
+        Background.two_sided(image, 25, 6, width=3)

specreduce/tracing.py

@@ -50,7 +50,8 @@ def shift(self, delta):
         delta : float
             Shift to be applied to the trace
         """
-        self.trace += delta
+        # act on self.trace.data to ignore the mask and then re-mask when calling _bound_trace
+        self.trace = np.asarray(self.trace.data) + delta
         self._bound_trace()
 
     def _bound_trace(self):