Add argument to toggle empty can run

Author: jl-wynen

docs/user-guide/dream/dream-powder-reduction.ipynb

@@ -56,7 +56,10 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "workflow = dream.DreamGeant4Workflow(run_norm=powder.RunNormalization.monitor_histogram)"
+    "workflow = dream.DreamGeant4Workflow(\n",
+    "    run_norm=powder.RunNormalization.monitor_histogram,\n",
+    "    subtract_empty_can=True,\n",
+    ")"
    ]
   },
   {
@@ -94,10 +97,7 @@
     "workflow[DspacingBins] = sc.linspace(\"dspacing\", 0.3, 2.3434, 201, unit=\"angstrom\")\n",
     "\n",
     "# Do not mask any pixels / voxels:\n",
-    "workflow = powder.with_pixel_mask_filenames(workflow, [])\n",
-    "\n",
-    "# Enable subtraction by an empty can measurement:\n",
-    "powder.correction.add_empty_can_subtraction(workflow)"
+    "workflow = powder.with_pixel_mask_filenames(workflow, [])"
    ]
   },
   {

src/ess/dream/workflow.py

@@ -15,6 +15,7 @@
 from ess.powder.conversion import convert_monitor_to_wavelength
 from ess.powder.correction import (
     RunNormalization,
+    add_empty_can_subtraction,
     insert_run_normalization,
 )
 from ess.powder.types import (
@@ -114,16 +115,34 @@ def convert_dream_monitor_to_wavelength(
     return convert_monitor_to_wavelength(monitor)
 
 
-def DreamGeant4Workflow(*, run_norm: RunNormalization) -> sciline.Pipeline:
+def DreamGeant4Workflow(
+    *, run_norm: RunNormalization, subtract_empty_can: bool = False
+) -> sciline.Pipeline:
     """
     Workflow with default parameters for the Dream Geant4 simulation.
+
+    Parameters
+    ----------
+    run_norm:
+        Select how to normalize each run (sample, vanadium, etc.).
+    subtract_empty_can:
+        If ``True``, subtract the same data by an empty can / empty instrument
+        measurement before normalizing by vanadium.
+        This requires specifying a filename parameter for the empty can run.
+
+    Returns
+    -------
+    :
+        A workflow object for DREAM.
     """
     wf = LoadGeant4Workflow()
     for provider in itertools.chain(powder_providers, _dream_providers):
         wf.insert(provider)
     wf.insert(convert_dream_monitor_to_wavelength)
     wf.insert(resample_monitor_time_of_flight_data)
     insert_run_normalization(wf, run_norm)
+    if subtract_empty_can:
+        add_empty_can_subtraction(wf)
     for key, value in itertools.chain(
         default_parameters().items(), time_of_flight.default_parameters().items()
     ):