fix bug finding focus in stack with only one slice (#162)

* fix bug finding focus in stack with only one slice

* refactor for clarify

* formatting

* print -> warnings.warn

* test single-slice case

* fix test bugs

---------

Co-authored-by: Talon Chandler <[email protected]>

tests/test_focus_estimator.py

@@ -39,12 +39,21 @@ def test_focus_estimator(tmp_path):
     plot_path = tmp_path.joinpath("test.pdf")
     data3D = np.random.random((11, 256, 256))
     slice = focus.focus_from_transverse_band(
-        data3D, ps, lambda_ill, NA_det, plot_path=str(plot_path)
+        data3D, NA_det, lambda_ill, ps, plot_path=str(plot_path)
     )
     assert slice >= 0
     assert slice <= data3D.shape[0]
     assert plot_path.exists()
 
+    # Check single slice
+    slice = focus.focus_from_transverse_band(
+        np.random.random((1, 10, 10)),
+        NA_det,
+        lambda_ill,
+        ps,
+    )
+    assert slice == 0
+
 
 def test_focus_estimator_snr(tmp_path):
     ps = 6.5 / 100
@@ -66,9 +75,9 @@ def test_focus_estimator_snr(tmp_path):
         plot_path = tmp_path / f"test-{snr}.pdf"
         slice = focus.focus_from_transverse_band(
             data,
-            ps,
-            lambda_ill,
             NA_det,
+            lambda_ill,
+            ps,
             plot_path=plot_path,
             threshold_FWHM=5,
         )

waveorder/focus.py

@@ -3,6 +3,7 @@
 from waveorder import util
 import matplotlib.pyplot as plt
 import numpy as np
+import warnings
 
 
 def focus_from_transverse_band(
@@ -60,10 +61,19 @@ def focus_from_transverse_band(
     >>> slice = focus_from_transverse_band(zyx_array, NA_det=0.55, lambda_ill=0.532, pixel_size=6.5/20)
     >>> in_focus_data = data[slice,:,:]
     """
-    minmaxfunc = _check_focus_inputs(
-        zyx_array, NA_det, lambda_ill, pixel_size, midband_fractions, mode
+    minmaxfunc = _mode_to_minmaxfunc(mode)
+
+    _check_focus_inputs(
+        zyx_array, NA_det, lambda_ill, pixel_size, midband_fractions
     )
 
+    # Check for single slice
+    if zyx_array.shape[0] == 1:
+        warnings.warn(
+            "The dataset only contained a single slice. Returning trivial slice index = 0."
+        )
+        return 0
+
     # Calculate coordinates
     _, Y, X = zyx_array.shape
     _, _, fxx, fyy = util.gen_coordinate((Y, X), pixel_size)
@@ -94,25 +104,35 @@ def focus_from_transverse_band(
     # Plot
     if plot_path is not None:
         _plot_focus_metric(
-            plot_path, midband_sum, peak_index, in_focus_index, peak_results, threshold_FWHM
+            plot_path,
+            midband_sum,
+            peak_index,
+            in_focus_index,
+            peak_results,
+            threshold_FWHM,
         )
 
     return in_focus_index
 
 
+def _mode_to_minmaxfunc(mode):
+    if mode == "min":
+        minmaxfunc = np.argmin
+    elif mode == "max":
+        minmaxfunc = np.argmax
+    else:
+        raise ValueError("mode must be either `min` or `max`")
+    return minmaxfunc
+
+
 def _check_focus_inputs(
-    zyx_array, NA_det, lambda_ill, pixel_size, midband_fractions, mode
+    zyx_array, NA_det, lambda_ill, pixel_size, midband_fractions
 ):
     N = len(zyx_array.shape)
     if N != 3:
         raise ValueError(
             f"{N}D array supplied. `focus_from_transverse_band` only accepts 3D arrays."
         )
-    if zyx_array.shape[0] == 1:
-        print(
-            "WARNING: The dataset only contained a single slice. Returning trivial slice index = 0."
-        )
-        return 0
 
     if NA_det < 0:
         raise ValueError("NA must be > 0")
@@ -121,7 +141,7 @@ def _check_focus_inputs(
     if pixel_size < 0:
         raise ValueError("pixel_size must be > 0")
     if not 0.4 < lambda_ill / pixel_size < 10:
-        print(
+        warnings.warn(
             f"WARNING: lambda_ill/pixel_size = {lambda_ill/pixel_size}."
             f"Did you use the same units?"
             f"Did you enter the pixel size in (demagnified) object-space units?"
@@ -134,17 +154,15 @@ def _check_focus_inputs(
         raise ValueError("midband_fractions[0] must be between 0 and 1")
     if not (0 <= midband_fractions[1] <= 1):
         raise ValueError("midband_fractions[1] must be between 0 and 1")
-    if mode == "min":
-        minmaxfunc = np.argmin
-    elif mode == "max":
-        minmaxfunc = np.argmax
-    else:
-        raise ValueError("mode must be either `min` or `max`")
-    return minmaxfunc
 
 
 def _plot_focus_metric(
-    plot_path, midband_sum, peak_index, in_focus_index, peak_results, threshold_FWHM
+    plot_path,
+    midband_sum,
+    peak_index,
+    in_focus_index,
+    peak_results,
+    threshold_FWHM,
 ):
     _, ax = plt.subplots(1, 1, figsize=(4, 4))
     ax.plot(midband_sum, "-k")