Merge pull request #741 from Manny7717/fix/ewa-fill-value

Fix user fill value not being used in EWA

Author: djhoese

pyresample/ewa/ewa.py

@@ -108,7 +108,8 @@ def fornav(cols, rows, area_def, data_in,
         If `data_in` is made of numpy arrays then this represents the fill
         value used to mark invalid data pixels. This value will also be
         used in the output array(s). If None, then np.nan will be used
-        for float arrays and -999 will be used for integer arrays.
+        for float arrays and the maximum value of the data type will be
+        used for integer arrays (ex. 127 for int8).
     out : numpy array or tuple of numpy arrays, optional
         Specify a numpy array to be written to for each input array. This can
         be used as an optimization by providing `np.memmap` arrays or other
@@ -167,7 +168,7 @@ def fornav(cols, rows, area_def, data_in,
     rows_per_scan = rows_per_scan or data_in[0].shape[0]
 
     results = _fornav.fornav_wrapper(cols, rows, data_in, out,
-                                     np.nan, np.nan, rows_per_scan,
+                                     fill, fill, rows_per_scan,
                                      weight_count=weight_count,
                                      weight_min=weight_min,
                                      weight_distance_max=weight_distance_max,
@@ -208,7 +209,7 @@ def _data_in_as_masked_arrays(
         if np.issubdtype(data_in[0].dtype, np.floating):
             fill = np.nan
         elif np.issubdtype(data_in[0].dtype, np.integer):
-            fill = -999
+            fill = np.iinfo(data_in[0].dtype).max
         else:
             raise ValueError(
                 "Unsupported input data type for EWA Resampling: {}".format(data_in[0].dtype))

pyresample/test/test_ewa_fornav.py

@@ -194,6 +194,49 @@ def test_fornav_swath_larger_float32(self):
                         msg="Unexpected interpolation values were returned")
 
 
+def _partial_coverage_swath(dtype):
+    """Create an all-ones swath that covers only part of a 1000x1000 grid.
+
+    The right side of the grid is left uncovered so the output is guaranteed
+    to contain fill pixels as well as data pixels.
+    """
+    swath_shape = (1600, 3200)
+    rows = np.empty(swath_shape, dtype=np.float32)
+    rows[:] = np.linspace(-500, 2500, swath_shape[0])[:, None]
+    cols = np.empty(swath_shape, dtype=np.float32)
+    cols[:] = np.linspace(-2500, 500, swath_shape[1])
+    data = np.ones(swath_shape, dtype=dtype)
+    out = np.empty((1000, 1000), dtype=dtype)
+    return cols, rows, data, out
+
+
+@pytest.mark.parametrize(
+    ("dtype", "fill", "expected_fill"),
+    [
+        (np.int8, 0, 0),
+        (np.int8, None, 127),
+        (np.float32, 0.0, 0.0),
+        (np.float32, None, np.nan),
+        (np.float64, -999.0, -999.0),
+        (np.float64, np.nan, np.nan),
+    ],
+)
+def test_fornav_fill_used_in_output(dtype, fill, expected_fill):
+    """Test that the user-supplied or default fill value is written to uncovered pixels (#689)."""
+    from pyresample.ewa import fornav
+    cols, rows, data, out = _partial_coverage_swath(dtype)
+
+    grid_points_covered, out_res = fornav(cols, rows, None, data,
+                                          rows_per_scan=16, fill=fill, out=out)
+
+    assert out is out_res
+    assert grid_points_covered > 0
+    # The swath was all 1s so every grid cell is either data or the fill value
+    is_fill = np.isnan(out) if np.isnan(expected_fill) else out == expected_fill
+    assert ((out == 1) | is_fill).all(), "Output should only contain data and fill values"
+    assert is_fill.any(), "Uncovered pixels should contain the fill value"
+
+
 @pytest.mark.parametrize(
     ("dtype", "input_fill", "output_fill"),
     [