feat: Implement background depth distance feature for depth processing

- Added `background_depth_distance` property to `ActiveJob` and `RunJob` classes to manage background depth settings.
- Updated job execution to handle background depth distance, allowing for fixed negative displacement in depth calculations.
- Introduced new functions in the worker module to apply background depth distance to depth frames and manage original background depth.
- Enhanced tests to cover new functionality, ensuring correct behavior of background depth processing and reference depth extraction.
- Refactored job submission to run in a separate thread, improving responsiveness during execution.

tests/test_image_depth.py

@@ -87,6 +87,21 @@ class ImageDepthTest(unittest.TestCase):
 
         self.assertEqual(depth.shape, (2, 3))
 
+    def test_extracts_optional_reference_depth(self):
+        with tempfile.TemporaryDirectory() as directory:
+            npz_path = Path(directory) / "results.npz"
+            np.savez_compressed(
+                npz_path,
+                depth=np.ones((1, 2, 2), dtype=np.float32),
+                snapform_reference_depth=np.float32(2.5),
+            )
+
+            reference_depth = self.image_depth.extract_reference_depth(
+                npz_path
+            )
+
+        self.assertEqual(reference_depth, 2.5)
+
     def test_is_animated_image_accepts_movie_and_sequence(self):
         self.assertTrue(
             self.image_depth.is_animated_image(
@@ -430,6 +445,28 @@ class ImageDepthTest(unittest.TestCase):
 
         self.assertEqual(bounds, (-1.0, 1.0, -0.5, 0.5))
 
+    def test_camera_plane_bounds_use_stored_unmasked_reference_depth(self):
+        source = SimpleNamespace(
+            data=SimpleNamespace(size=(200, 100)),
+            empty_image_offset=(-0.5, -0.5),
+        )
+        depth = np.full((100, 200), 9.0, dtype=np.float32)
+        intrinsics = np.array(
+            ((100.0, 0.0, 100.0), (0.0, 100.0, 50.0), (0.0, 0.0, 1.0)),
+            dtype=np.float32,
+        )
+
+        bounds, reference_depth = self.image_depth.camera_plane_bounds(
+            source,
+            depth,
+            intrinsics,
+            -1.0,
+            reference_depth=2.0,
+        )
+
+        self.assertEqual(bounds, (-2.0, 2.0, -1.0, 1.0))
+        self.assertEqual(reference_depth, 2.0)
+
     def test_camera_plane_bounds_preserve_square_source_aspect(self):
         source = SimpleNamespace(
             data=SimpleNamespace(size=(447, 447)),
@@ -460,20 +497,33 @@ class ImageDepthTest(unittest.TestCase):
 
     def test_raw_distance_preserves_original_values(self):
         depth = np.array(
-            ((1.25, 2.5), (5.0, np.nan)),
+            ((1.25, -2.5), (0.0, np.nan)),
             dtype=np.float32,
         )
 
         mapped = self.image_depth.prepare_depth_values(depth)
 
         self.assertEqual(float(mapped[0, 0]), 1.25)
-        self.assertEqual(float(mapped[0, 1]), 2.5)
-        self.assertEqual(float(mapped[1, 0]), 5.0)
+        self.assertEqual(float(mapped[0, 1]), -2.5)
+        self.assertEqual(float(mapped[1, 0]), 0.0)
         self.assertEqual(float(mapped[1, 1]), 0.0)
 
+    def test_depth_values_are_scaled_before_creating_depth_image(self):
+        depth = np.array(
+            ((0.5, -1.0), (0.0, 2.0)),
+            dtype=np.float32,
+        )
+
+        scaled = self.image_depth.scale_depth_values(depth, 4.1)
+
+        np.testing.assert_allclose(
+            scaled,
+            ((2.05, -4.1), (0.0, 8.2)),
+        )
+
     def test_depth_plane_uses_fixed_import_settings(self):
-        self.assertEqual(self.image_depth.DISPLACEMENT_STRENGTH, -1.0)
-        self.assertEqual(self.image_depth.DISPLACEMENT_MIDLEVEL, 1.0)
+        self.assertEqual(self.image_depth.DISPLACEMENT_STRENGTH, 1.0)
+        self.assertEqual(self.image_depth.DISPLACEMENT_MIDLEVEL, 0.0)
         self.assertEqual(self.image_depth.BUMP_BASE_DISTANCE, 0.001)
 
     def test_grid_segments_follow_aspect_ratio_from_subdivision_power(self):