Enable detector-view pixel weighting by default

src/ess/livedata/config/models.py

@@ -19,21 +19,26 @@
 
 class WeightingMethod(StrEnum):
     """
-    Methods for pixel weighting.
+    How the weight of an image pixel is computed.
 
-    - PIXEL_NUMBER: Weight by the number of detector pixels contributing to each screen
-        pixel.
+    - PIXEL_NUMBER: The number of detector pixels that map to the image pixel.
     """
 
     PIXEL_NUMBER = 'pixel_number'
 
 
 class PixelWeighting(BaseModel):
-    """Setting for pixel weighting."""
+    """Divides a detector image by a weight per image pixel."""
 
-    enabled: bool = Field(default=False, description="Enable pixel weighting.")
+    enabled: bool = Field(
+        default=True,
+        description="Divide each image pixel by its weight, so that the image shows "
+        "counts per detector pixel.",
+    )
     method: WeightingMethod = Field(
-        default=WeightingMethod.PIXEL_NUMBER, description="Method for pixel weighting."
+        default=WeightingMethod.PIXEL_NUMBER,
+        description="How the weight of an image pixel is computed. 'pixel_number': "
+        "the number of detector pixels that map to the image pixel.",
     )
 
 

src/ess/livedata/workflows/detector_view/factory.py

@@ -139,9 +139,6 @@ def make_workflow(
         bins = params.get_active_edges()
         histogram_slice = params.get_active_range()
 
-        # Get pixel weighting setting from params
-        use_pixel_weighting = params.pixel_weighting.enabled
-
         # Create base workflow with appropriate mode
         workflow = create_base_workflow(
             bins=bins,
@@ -163,8 +160,7 @@ def make_workflow(
         # Configure detector data source (EmptyDetector)
         self._data_source.configure_workflow(workflow, source_name)
 
-        # Set pixel weighting configuration
-        workflow[UsePixelWeighting] = use_pixel_weighting
+        workflow[UsePixelWeighting] = params.pixel_weighting.enabled
 
         # Add projection based on config type
         config = self._get_config(source_name)

src/ess/livedata/workflows/detector_view/providers.py

@@ -278,9 +278,10 @@ def detector_image(
     histogram_slice:
         Optional (low, high) range for slicing. If None, sum over full range.
     weights:
-        Pixel weights for normalization.
+        Number of detector pixels per image pixel.
     use_weighting:
-        Whether to apply pixel weighting.
+        Whether to divide the image by ``weights``, giving counts per detector
+        pixel. Screen pixels without detector pixels then become 0/0 = NaN.
 
     Returns
     -------

src/ess/livedata/workflows/detector_view/workflow.py

@@ -62,7 +62,6 @@
     LogicalTransform,
     ProjectionType,
     ReductionDim,
-    UsePixelWeighting,
 )
 
 
@@ -77,7 +76,8 @@ def create_base_workflow(
     Create the base detector view workflow.
 
     This creates the core workflow with all providers. The Projector param
-    must be set separately via add_geometric_projection or add_logical_projection.
+    must be set separately via add_geometric_projection or add_logical_projection,
+    and UsePixelWeighting by the caller.
 
     Parameters
     ----------
@@ -116,7 +116,6 @@ def create_base_workflow(
 
     # Add pixel weighting provider
     workflow.insert(compute_pixel_weights)
-    workflow[UsePixelWeighting] = False  # Default: disabled
 
     # Add histogram and downstream providers (generic providers for both modes).
     # detector_geometry stamps the move-detection coord; file-less sources override

src/ess/livedata/workflows/detector_view_specs.py

@@ -92,11 +92,20 @@ class DetectorViewParamsBase(pydantic.BaseModel, abc.ABC):
     )
     pixel_weighting: models.PixelWeighting = pydantic.Field(
         title="Pixel Weighting",
-        description="Whether to apply pixel weighting based on the number of pixels "
-        "contributing to each screen pixel.",
-        default=models.PixelWeighting(
-            enabled=False, method=models.WeightingMethod.PIXEL_NUMBER
+        description=(
+            "Divide each image pixel by the number of detector pixels that map to "
+            "it, so that the image shows counts per detector pixel. In geometric "
+            "projections (xy-plane, cylinder) this number varies across the image "
+            "and is averaged over the position noise, so it can be fractional at "
+            "module edges. Without weighting, the image shows pixel density as "
+            "well as count rate. Image pixels that no detector pixel maps to, such "
+            "as gaps between detector modules, have no value (NaN). In logical "
+            "views every image pixel has the same number of detector pixels, so "
+            "weighting has no effect or divides the whole image by a constant. ROI "
+            "outputs stay summed counts. To show them per detector pixel, use "
+            "'Per Detector Pixel' in the plot settings."
         ),
+        default_factory=models.PixelWeighting,
     )
 
     @abc.abstractmethod
@@ -305,7 +314,8 @@ def _make_roi_spectra_template() -> sc.DataArray:
         fields=('cumulative', 'current'),
         description=(
             'Detector image. With "since run start" shows accumulated counts; '
-            'with "latest update" or a window, shows recent counts.'
+            'with "latest update" or a window, shows recent counts. With pixel '
+            'weighting, counts are per detector pixel.'
         ),
         params=(
             'coordinate_mode',

tests/config/dream_factories_test.py

@@ -9,6 +9,7 @@
 import scipp as sc
 
 from ess.livedata.config.instruments.dream import specs
+from ess.livedata.config.models import PixelWeighting
 from ess.livedata.config.workflow_spec import JobId, WorkflowConfig
 from ess.livedata.core.timestamp import Timestamp
 from ess.livedata.workflows.workflow_factory import SpecHandle
@@ -63,7 +64,10 @@ def test_logical_view_counts_every_event(
             identifier=handle.workflow_id,
             job_id=JobId(source_name=source_name, job_number=uuid.uuid4()),
         ),
-        params=factory[handle.workflow_id].params(),
+        # Unweighted, so that the image holds raw counts and sums to the events.
+        params=factory[handle.workflow_id].params(
+            pixel_weighting=PixelWeighting(enabled=False)
+        ),
     )
     workflow.accumulate(
         {source_name: _events(source_name, size=1000)},

tests/config/lut_streaming_end_to_end_test.py

@@ -571,7 +571,7 @@ def test_dream_prod_setpoints_empty_the_consumer(dream: Instrument) -> None:
 
     assert not reply.has_error, reply.error_message
     assert result.error_message is None, result.error_message
-    assert result.data['current'].sum().value == 0
+    assert result.data['current'].nansum().value == 0
 
 
 @pytest.fixture(scope='module')

tests/config/models_test.py

@@ -14,13 +14,13 @@ def test_weighting_method_values():
 
 def test_pixel_weighting_defaults():
     weight = models.PixelWeighting()
-    assert not weight.enabled
+    assert weight.enabled
     assert weight.method == models.WeightingMethod.PIXEL_NUMBER
 
 
 def test_pixel_weighting_custom():
-    weight = models.PixelWeighting(enabled=True)
-    assert weight.enabled
+    weight = models.PixelWeighting(enabled=False)
+    assert not weight.enabled
 
 
 def test_pixel_weighting_invalid_method():

tests/dashboard/ui_config_fixtures/dummy/workflow_configs.yaml

@@ -35,7 +35,7 @@ dummy/panel_0_layers/1:
         coordinate_mode:
           mode: toa
         pixel_weighting:
-          enabled: false
+          enabled: true
           method: pixel_number
         toa_edges:
           num_bins: 100
@@ -69,7 +69,7 @@ dummy/panel_0_xy/1:
         coordinate_mode:
           mode: toa
         pixel_weighting:
-          enabled: false
+          enabled: true
           method: pixel_number
         toa_edges:
           num_bins: 100

tests/services/detector_data_test.py

@@ -45,6 +45,10 @@ def _get_workflow_from_registry(
     raise ValueError(f"Namespace {namespace} not found in specs")
 
 
+# Pixel weighting off, so that image sums equal the number of published events.
+_UNWEIGHTED = {'pixel_weighting': {'enabled': False}}
+
+
 def make_detector_app(instrument: str) -> LivedataApp:
     builder = make_detector_service_builder(instrument=instrument)
     return LivedataApp.from_service_builder(builder)
@@ -76,7 +80,9 @@ def test_can_configure_and_stop_detector_workflow(
 
     source_name = detector_source_name[instrument]
     workflow_config = workflow_spec.WorkflowConfig(
-        identifier=workflow_id, job_id=_job_id(source_name)
+        identifier=workflow_id,
+        job_id=_job_id(source_name),
+        params=_UNWEIGHTED,
     )
     # Trigger workflow start
     app.publish_config_message(workflow_config)
@@ -150,7 +156,9 @@ def test_loki_cumulative_resets_when_detector_carriage_moves() -> None:
 
     source_name = 'loki_detector_0'
     workflow_config = workflow_spec.WorkflowConfig(
-        identifier=workflow_id, job_id=_job_id(source_name)
+        identifier=workflow_id,
+        job_id=_job_id(source_name),
+        params=_UNWEIGHTED,
     )
     app.publish_config_message(workflow_config)
     service.step()

tests/workflows/detector_view/factory_test.py

@@ -2,16 +2,22 @@
 # Copyright (c) 2025 Scipp contributors (https://github.com/scipp)
 """Tests for DetectorViewScilineFactory."""
 
+import numpy as np
+import pytest
 import scipp as sc
+from ess.reduce.nexus.types import RawDetector, SampleRun
 
+from ess.livedata.config.models import PixelWeighting
+from ess.livedata.core.timestamp import Timestamp
 from ess.livedata.workflows.detector_view.data_source import DetectorNumberSource
 from ess.livedata.workflows.detector_view.factory import DetectorViewFactory
 from ess.livedata.workflows.detector_view.types import (
     GeometricViewConfig,
     LogicalViewConfig,
 )
+from ess.livedata.workflows.detector_view_specs import DetectorViewParams
 
-from .utils import make_fake_detector_number
+from .utils import make_fake_detector_number, make_fake_nexus_detector_data
 
 
 class TestDetectorViewScilineFactory:
@@ -66,3 +72,44 @@ def transform(da: sc.DataArray, source_name: str) -> sc.DataArray:
         assert factory is not None
         assert isinstance(factory._get_config('source_a'), LogicalViewConfig)
         assert isinstance(factory._get_config('source_b'), GeometricViewConfig)
+
+
+@pytest.mark.parametrize(
+    ('reduction_dim', 'image_sizes', 'pixels_per_image_pixel'),
+    [(None, {'y': 4, 'x': 4}, 1), ('y', {'x': 4}, 4)],
+)
+@pytest.mark.parametrize('enabled', [True, False])
+def test_logical_view_image_with_pixel_weighting(
+    reduction_dim: str | None,
+    image_sizes: dict[str, int],
+    pixels_per_image_pixel: int,
+    enabled: bool,
+) -> None:
+    n_events_per_pixel = 10
+
+    def transform(da: sc.DataArray, source_name: str) -> sc.DataArray:
+        return da.fold(dim='detector_number', sizes={'y': 4, 'x': 4})
+
+    factory = DetectorViewFactory(
+        data_source=DetectorNumberSource(make_fake_detector_number(4, 4)),
+        view_config=LogicalViewConfig(
+            transform=transform, reduction_dim=reduction_dim, roi_support=False
+        ),
+    )
+    params = DetectorViewParams(pixel_weighting=PixelWeighting(enabled=enabled))
+    workflow = factory.make_workflow('detector', params=params)
+    workflow.build()
+    events = make_fake_nexus_detector_data(
+        y_size=4, x_size=4, n_events_per_pixel=n_events_per_pixel
+    )
+    workflow.accumulate(
+        {'detector': RawDetector[SampleRun](events)},
+        start_time=Timestamp.from_ns(1000),
+        end_time=Timestamp.from_ns(2000),
+    )
+
+    image = workflow.finalize()['cumulative']
+
+    assert image.sizes == image_sizes
+    expected = n_events_per_pixel * (1 if enabled else pixels_per_image_pixel)
+    np.testing.assert_array_equal(image.values, expected)