Add format class for I19-2 Eiger with DAC shadow (#481)

Also, Remove redundant file mode "r". This has been the default since
h5py 3.0 and DIALS/DXTBX ship with >=3.1.

newsfragments/481.bugfix

@@ -0,0 +1 @@
+``FormatNXmxI19_2``:  Allow data from beamline I19-2 at Diamond Light Source to be processed with optional masking of the beamline's standard diamond anvil pressure cell with a 76° aperture.

src/dxtbx/format/FormatNXmx.py

@@ -1,20 +1,26 @@
 from __future__ import annotations
 
+import math
+
 import h5py
 
+from libtbx import Auto
+
 import dxtbx.nexus
 from dxtbx.format.FormatNexus import FormatNexus
+from dxtbx.masking import GoniometerMaskerFactory
 
 
 class FormatNXmx(FormatNexus):
+    """Read NXmx-flavour NeXus-format HDF5 data."""
 
     _cached_file_handle = None
 
     @staticmethod
     def understand(image_file):
-        with h5py.File(image_file, "r", swmr=True) as handle:
+        """This format class currently only applies to beamline I19-2 at DLS."""
+        with h5py.File(image_file, swmr=True) as handle:
             name = dxtbx.nexus.nxmx.h5str(FormatNXmx.get_instrument_name(handle))
-        # Temporarily restrict this to I19-2 while developing
         if name and "I19-2" in name:
             return True
         return False
@@ -26,7 +32,7 @@ def __init__(self, image_file, **kwargs):
     def _start(self):
         self._static_mask = None
 
-        with h5py.File(self._image_file, "r", swmr=True) as fh:
+        with h5py.File(self._image_file, swmr=True) as fh:
             nxmx = dxtbx.nexus.nxmx.NXmx(fh)
             nxsample = nxmx.entries[0].samples[0]
             nxinstrument = nxmx.entries[0].instruments[0]
@@ -61,7 +67,7 @@ def get_static_mask(self, index=None, goniometer=None):
 
     def get_raw_data(self, index):
         if self._cached_file_handle is None:
-            self._cached_file_handle = h5py.File(self._image_file, "r", swmr=True)
+            self._cached_file_handle = h5py.File(self._image_file, swmr=True)
 
         nxmx = dxtbx.nexus.nxmx.NXmx(self._cached_file_handle)
         nxdata = nxmx.entries[0].data[0]
@@ -79,3 +85,43 @@ def get_raw_data(self, index):
                 d1d.set_selected(d1d == top - 1, -1)
                 d1d.set_selected(d1d == top - 2, -2)
         return raw_data
+
+
+class FormatNXmxI19_2(FormatNXmx):
+    """
+    Read NXmx-flavour data from beamline I19-2 at Diamond Light Source.
+
+    Include the option of dynamic shadowing of the standard I19-2 diamond anvil
+    pressure cell with a 76° conical aperture.
+    """
+
+    @staticmethod
+    def understand(image_file):
+        """This format class applies if the instrument name contains 'I19-2'."""
+        with h5py.File(image_file, swmr=True) as handle:
+            name = dxtbx.nexus.nxmx.h5str(FormatNXmx.get_instrument_name(handle))
+        if name and "I19-2" in name:
+            return True
+        return False
+
+    @staticmethod
+    def has_dynamic_shadowing(**kwargs):
+        """Check if dynamic shadowing should be applied for a diamond anvil cell."""
+        dynamic_shadowing = kwargs.get("dynamic_shadowing", False)
+        if dynamic_shadowing in (Auto, "Auto"):
+            return False
+        return dynamic_shadowing
+
+    def __init__(self, image_file, **kwargs):
+        """Initialise the image structure from the given file."""
+        self._dynamic_shadowing = self.has_dynamic_shadowing(**kwargs)
+        super().__init__(image_file, **kwargs)
+
+    def get_goniometer_shadow_masker(self, goniometer=None):
+        """Apply the dynamic mask for a diamond anvil cell with a 76° aperture."""
+        if goniometer is None:
+            goniometer = self.get_goniometer()
+
+        return GoniometerMaskerFactory.diamond_anvil_cell(
+            goniometer, cone_opening_angle=math.radians(76)
+        )