fix(v5): average noisy copies from clean source

backend/processing/services.py

@@ -165,6 +165,8 @@ def image_state_apply_operation(*, state, operation, params):
         return image_state_fft_spectrum_create(state=state, params=params or {})
     if operation == "inverse_fft_reconstruction":
         return image_state_inverse_fft_create(state=state, params=params or {})
+    if operation == "average_noisy_copies":
+        return image_state_average_noisy_copies_create(state=state, params=params or {})
 
     source = load_image_array(state.image)
     result = apply_registered_operation(source, operation, params or {})
@@ -180,6 +182,40 @@ def image_state_apply_operation(*, state, operation, params):
     return image_state_payload(state=new_state, include_image=True)
 
 
+def image_state_average_noisy_copies_create(*, state, params):
+    """Create averaged noisy copies from the clean source behind a Gaussian-noise state.
+
+    If the active state is already a Gaussian-noisy image, the averaging must regenerate independent
+    noisy copies from its parent image, not from the already-noisy pixels.
+    """
+
+    source_state = state
+    if (
+        state.operation == "noise_filter"
+        and isinstance(state.params, dict)
+        and state.params.get("kind", "gaussian") == "gaussian"
+        and state.parent is not None
+    ):
+        source_state = state.parent
+
+    operation_params = dict(params or {})
+    if source_state.id != state.id:
+        operation_params["source_state_id"] = str(source_state.id)
+
+    source = load_image_array(source_state.image)
+    result = apply_registered_operation(source, "average_noisy_copies", operation_params)
+    new_state = image_state_create(
+        session=state.session,
+        parent=state,
+        image=result,
+        operation="average_noisy_copies",
+        params=operation_params,
+        label=None,
+        prefix="state-average_noisy_copies",
+    )
+    return image_state_payload(state=new_state, include_image=True)
+
+
 def image_state_fft_spectrum_create(*, state, params):
     """Create an FFT visualization state and persist the actual complex spectrum.
 

backend/processing/tests/test_api.py

@@ -233,6 +233,29 @@ class ApiTests(TestCase):
         self.assertEqual(result.ndim, 2)
         self.assertEqual(int(result[0, 0]), 96)
 
+    def test_average_noisy_copies_uses_clean_parent_after_gaussian_noise_state(self):
+        upload = self.client.post("/api/images/", {"image": grayscale_png_upload(value=96)}, format="multipart")
+        s0_id = upload.data["states"][0]["state_id"]
+        noisy = self.client.post(
+            f"/api/states/{s0_id}/operations/",
+            {"operation": "noise_filter", "params": {"kind": "gaussian", "mean": 0.2, "variance": 0}},
+            format="json",
+        )
+        noisy_image = load_image_array(ImageState.objects.get(id=noisy.data["state_id"]).image)
+        self.assertGreater(int(noisy_image[0, 0]), 96)
+
+        averaged = self.client.post(
+            f"/api/states/{noisy.data['state_id']}/operations/",
+            {"operation": "average_noisy_copies", "params": {"N": 10, "kind": "gaussian", "mean": 0, "variance": 0}},
+            format="json",
+        )
+
+        self.assertEqual(averaged.status_code, 201)
+        self.assertEqual(averaged.data["parent_state_id"], noisy.data["state_id"])
+        self.assertEqual(averaged.data["params"]["source_state_id"], s0_id)
+        result = load_image_array(ImageState.objects.get(id=averaged.data["state_id"]).image)
+        self.assertEqual(int(result[0, 0]), 96)
+
     def test_periodic_noise_preserves_grayscale_and_zero_amplitude(self):
         upload = self.client.post("/api/images/", {"image": grayscale_png_upload(value=96)}, format="multipart")
         s0_id = upload.data["states"][0]["state_id"]