feat: implement scale_factor and add_offset getters for both readers

python/omfiles/_rust/__init__.pyi

@@ -103,6 +103,22 @@ class OmFileReader:
             str: Compression type of the variable.
         """
     @property
+    def scale_factor(self) -> builtins.float:
+        r"""
+        Get the scale factor of the variable.
+
+        Returns:
+            float: Scale factor stored in the array metadata.
+        """
+    @property
+    def add_offset(self) -> builtins.float:
+        r"""
+        Get the add offset of the variable.
+
+        Returns:
+            float: Add offset stored in the array metadata.
+        """
+    @property
     def num_children(self) -> builtins.int:
         r"""
         Number of children of the variable.
@@ -355,6 +371,22 @@ class OmFileReaderAsync:
             str: Compression type of the variable.
         """
     @property
+    def scale_factor(self) -> builtins.float:
+        r"""
+        Get the scale factor of the variable.
+
+        Returns:
+            float: Scale factor stored in the array metadata.
+        """
+    @property
+    def add_offset(self) -> builtins.float:
+        r"""
+        Get the add offset of the variable.
+
+        Returns:
+            float: Add offset stored in the array metadata.
+        """
+    @property
     def num_children(self) -> builtins.int:
         r"""
         Number of children of the variable.

src/reader.rs

@@ -412,6 +412,34 @@ impl OmFileReader {
         })
     }
 
+    /// Get the scale factor of the variable.
+    ///
+    /// Returns:
+    ///     float: Scale factor stored in the array metadata.
+    #[getter]
+    fn scale_factor(&self) -> PyResult<f32> {
+        self.with_reader(|reader| {
+            Ok(reader
+                .expect_array()
+                .map_err(|_| Self::only_arrays_error())?
+                .scale_factor())
+        })
+    }
+
+    /// Get the add offset of the variable.
+    ///
+    /// Returns:
+    ///     float: Add offset stored in the array metadata.
+    #[getter]
+    fn add_offset(&self) -> PyResult<f32> {
+        self.with_reader(|reader| {
+            Ok(reader
+                .expect_array()
+                .map_err(|_| Self::only_arrays_error())?
+                .add_offset())
+        })
+    }
+
     /// Number of children of the variable.
     ///
     /// Returns:

src/reader_async.rs

@@ -365,6 +365,34 @@ impl OmFileReaderAsync {
         })
     }
 
+    /// Get the scale factor of the variable.
+    ///
+    /// Returns:
+    ///     float: Scale factor stored in the array metadata.
+    #[getter]
+    fn scale_factor(&self) -> PyResult<f32> {
+        self.with_reader(|reader| {
+            Ok(reader
+                .expect_array()
+                .map_err(|_| Self::only_arrays_error())?
+                .scale_factor())
+        })
+    }
+
+    /// Get the add offset of the variable.
+    ///
+    /// Returns:
+    ///     float: Add offset stored in the array metadata.
+    #[getter]
+    fn add_offset(&self) -> PyResult<f32> {
+        self.with_reader(|reader| {
+            Ok(reader
+                .expect_array()
+                .map_err(|_| Self::only_arrays_error())?
+                .add_offset())
+        })
+    }
+
     /// Number of children of the variable.
     ///
     /// Returns:

tests/test_read_write.py

@@ -49,6 +49,8 @@ def test_round_trip_array_datatypes():
 
             # Read data back
             reader = omfiles.OmFileReader(temp_file.name)
+            assert reader.scale_factor == 10000.0
+            assert reader.add_offset == 0.0
             read_data = reader[:]
             reader.close()
 
@@ -68,6 +70,8 @@ def test_write_contiguous_array_succeeds(empty_temp_om_file):
     writer.close(variable)
 
     reader = omfiles.OmFileReader(empty_temp_om_file)
+    assert reader.scale_factor == 10000.0
+    assert reader.add_offset == 0.0
     read_data = reader[:]
     reader.close()
 
@@ -116,7 +120,7 @@ def test_write_hierarchical_file(empty_temp_om_file):
 
     # Write child1 array with attribute children
     child1_var = writer.write_array(
-        child1_data, chunks=[2, 2], name="child1", scale_factor=100000.0, children=[meta1_var, meta2_var, meta3_var]
+        child1_data, chunks=[2, 2], name="child1", scale_factor=10000.0, children=[meta1_var, meta2_var, meta3_var]
     )
 
     # Write root array with children
@@ -141,13 +145,17 @@ def test_write_hierarchical_file(empty_temp_om_file):
 
     # Verify child1 data
     child1_reader = reader._init_from_variable(child_metadata["/root/child1"])
+    assert child1_reader.scale_factor == 10000.0
+    assert child1_reader.add_offset == 0.0
     read_child1 = child1_reader[:]
     np.testing.assert_array_almost_equal(read_child1, child1_data, decimal=4)
     assert read_child1.shape == (5, 5)
     assert read_child1.dtype == np.float32
 
     # Verify child2 data
     child2_reader = reader._init_from_variable(child_metadata["/root/child2"])
+    assert child2_reader.scale_factor == 100000.0
+    assert child2_reader.add_offset == 0.0
     read_child2 = child2_reader[:]
     np.testing.assert_array_almost_equal(read_child2, child2_data, decimal=4)
     assert read_child2.shape == (3, 3)
@@ -172,6 +180,12 @@ def test_write_hierarchical_file(empty_temp_om_file):
     assert type(metadata3) == str
     assert metadata_reader3.dtype == str
 
+    for metadata_reader in [metadata_reader1, metadata_reader2, metadata_reader3]:
+        with pytest.raises(ValueError):
+            metadata_reader.scale_factor
+        with pytest.raises(ValueError):
+            metadata_reader.add_offset
+
     reader.close()
     child1_reader.close()
     child2_reader.close()
@@ -184,6 +198,8 @@ def test_write_hierarchical_file(empty_temp_om_file):
 async def test_read_async(temp_om_file):
     with await omfiles.OmFileReaderAsync.from_path(temp_om_file) as reader:
         # Test basic async read
+        assert reader.scale_factor == 1.0
+        assert reader.add_offset == 0.0
         data = await reader.read_array((slice(0, 5), ...))
         assert data.shape == (5, 5)
         assert data.dtype == np.float32
@@ -273,6 +289,10 @@ def test_child_traversal(temp_hierarchical_om_file):
     assert reader.dtype == type(None)
     with pytest.raises(ValueError):
         _ = reader.compression_name
+    with pytest.raises(ValueError):
+        _ = reader.scale_factor
+    with pytest.raises(ValueError):
+        _ = reader.add_offset
     with pytest.raises(ValueError):
         _ = reader.read_scalar()
     with pytest.raises(ValueError):