test src.downsample.pixel_size == src.img.downsample.pixel_size

Author: j-c-c

src/aspire/source/relion.py

@@ -43,7 +43,7 @@ def __init__(
         :param data_folder: Path to folder w.r.t which all relative paths to .mrcs files are resolved.
             If None, the folder corresponding to filepath is used.
         :param pixel_size: The pixel size of the images in angstroms. By default, pixel size is
-            populated from the STAR file if relevant metadata fields exist, otherwise set to 1.
+            populated from the STAR file if relevant metadata fields exist.
         :param B: the envelope decay of the CTF in inverse square angstrom (Default 0)
         :param n_workers: Number of threads to spawn to read referenced .mrcs files (Default -1 to auto detect)
         :param max_rows: Maximum number of rows in STAR file to read. If None, all rows are read.

tests/test_downsample.py

@@ -317,21 +317,27 @@ def test_downsample_offsets(dtype, res):
 
 def test_pixel_size():
     """
-    Test downsampling is rescaling the `pixel_size` attribute.
+    Test downsampling is rescaling the `pixel_size` attribute for both Images
+    and ImageSource objects.
     """
     # Image sizes in pixels
     L = 8  # original
     dsL = 5  # downsampled
+    n = 10  # num images
 
-    # Construct a small test Image
-    img = Image(np.random.random((1, L, L)).astype(DTYPE, copy=False), pixel_size=1.23)
+    # Construct small test ImageSource and Image instances
+    src = Simulation(L=L, n=n)
+    img = src.images[:]
 
-    # Downsample the image
-    result = img.downsample(dsL)
+    # Confirm the pixel size is scaled properly in both cases
+    np.testing.assert_approx_equal(
+        src.downsample(dsL).pixel_size,
+        src.pixel_size * L / dsL,
+        err_msg="Incorrect pixel size.",
+    )
 
-    # Confirm the pixel size is scaled
     np.testing.assert_approx_equal(
-        result.pixel_size,
+        img.downsample(dsL).pixel_size,
         img.pixel_size * L / dsL,
         err_msg="Incorrect pixel size.",
     )