ENH: expose FRB to enable buffer filtering within a PlotWindow

The name of the callback has in general no reason to start by `annotate_`. This is
to make space for a smooth callback

doc/source/visualizing/callbacks.rst

@@ -889,3 +889,20 @@ Overplot the Path of a Ray
    p.annotate_ray(oray)
    p.annotate_ray(ray)
    p.save()
+
+
+Applying filters on the final image
+-----------------------------------
+
+It is also possible to operate on the plotted image directly by using
+one of the fixed resolution buffer filter as described in
+:ref:`frb-filters`.
+
+.. python-script::
+
+   import yt
+
+   ds = yt.load('IsolatedGalaxy/galaxy0030/galaxy0030')
+   p = yt.SlicePlot(ds, 'z', 'density')
+   p.frb.apply_gauss_beam(sigma=30)
+   p.save()

yt/visualization/_commons.py

@@ -1,6 +1,7 @@
 import os
 import sys
 import warnings
+from functools import wraps
 from typing import Optional, Type
 
 import matplotlib
@@ -93,3 +94,57 @@ def get_canvas(figure, filename):
             f"without an extension."
         )
     return get_canvas_class(suffix)(figure)
+
+
+def invalidate_plot(f):
+    @wraps(f)
+    def newfunc(self, *args, **kwargs):
+        retv = f(self, *args, **kwargs)
+        self._plot_valid = False
+        return retv
+
+    return newfunc
+
+
+def invalidate_data(f):
+    @wraps(f)
+    def newfunc(self, *args, **kwargs):
+        retv = f(self, *args, **kwargs)
+        self._data_valid = False
+        self._plot_valid = False
+        return retv
+
+    return newfunc
+
+
+def invalidate_figure(f):
+    @wraps(f)
+    def newfunc(self, *args, **kwargs):
+        retv = f(self, *args, **kwargs)
+        for field in self.plots.keys():
+            self.plots[field].figure = None
+            self.plots[field].axes = None
+            self.plots[field].cax = None
+        self._setup_plots()
+        return retv
+
+    return newfunc
+
+
+def validate_plot(f):
+    @wraps(f)
+    def newfunc(self, *args, **kwargs):
+        # TODO: _profile_valid and _data_valid seem to play very similar roles,
+        # there's probably room to abstract these into a common operation
+        if hasattr(self, "_data_valid") and not self._data_valid:
+            self._recreate_frb()
+        if hasattr(self, "_profile_valid") and not self._profile_valid:
+            self._recreate_profile()
+        if not self._plot_valid:
+            # it is the responsibility of _setup_plots to
+            # call plot.run_callbacks()
+            self._setup_plots()
+        retv = f(self, *args, **kwargs)
+        return retv
+
+    return newfunc

yt/visualization/fixed_resolution.py

@@ -1,5 +1,6 @@
 import weakref
 from functools import wraps
+from typing import Dict, List, Optional
 
 import numpy as np
 
@@ -14,7 +15,11 @@
 from yt.utilities.lib.pixelization_routines import pixelize_cylinder
 from yt.utilities.on_demand_imports import _h5py as h5py
 
-from .fixed_resolution_filters import apply_filter, filter_registry
+from .fixed_resolution_filters import (
+    FixedResolutionBufferFilter,
+    apply_filter,
+    filter_registry,
+)
 from .volume_rendering.api import off_axis_projection
 
 
@@ -53,6 +58,8 @@ class FixedResolutionBuffer:
         This can be true or false, and governs whether the pixelization
         will span the domain boundaries.
 
+    filters : list of FixedResolutionBufferFilter objects (optional)
+
     Examples
     --------
     To make a projection and then several images, you can generate a
@@ -90,16 +97,27 @@ class FixedResolutionBuffer:
         ("index", "dtheta"),
     )
 
-    def __init__(self, data_source, bounds, buff_size, antialias=True, periodic=False):
+    def __init__(
+        self,
+        data_source,
+        bounds,
+        buff_size,
+        antialias=True,
+        periodic=False,
+        *,
+        filters: Optional[List[FixedResolutionBufferFilter]] = None,
+    ):
         self.data_source = data_source
         self.ds = data_source.ds
         self.bounds = bounds
         self.buff_size = (int(buff_size[0]), int(buff_size[1]))
         self.antialias = antialias
-        self.data = {}
+        self.data: Dict[str, np.ndarray] = {}
         self._filters = []
         self.axis = data_source.axis
         self.periodic = periodic
+        self._data_valid = False
+        self._filters = filters if filters is not None else []
 
         ds = getattr(data_source, "ds", None)
         if ds is not None:
@@ -125,7 +143,7 @@ def __delitem__(self, item):
         del self.data[item]
 
     def __getitem__(self, item):
-        if item in self.data:
+        if item in self.data and self._data_valid:
             return self.data[item]
         mylog.info(
             "Making a fixed resolution buffer of (%s) %d by %d",
@@ -165,6 +183,7 @@ def __getitem__(self, item):
 
         ia = ImageArray(buff, units=units, info=self._get_info(item))
         self.data[item] = ia
+        self._data_valid = True
         return self.data[item]
 
     def __setitem__(self, item, val):
@@ -542,14 +561,14 @@ class CylindricalFixedResolutionBuffer(FixedResolutionBuffer):
     that supports non-aligned input data objects, primarily cutting planes.
     """
 
-    def __init__(self, data_source, radius, buff_size, antialias=True):
-
+    def __init__(self, data_source, radius, buff_size, antialias=True, *, filters=None):
         self.data_source = data_source
         self.ds = data_source.ds
         self.radius = radius
         self.buff_size = buff_size
         self.antialias = antialias
         self.data = {}
+        self._filters = filters if filters is not None else []
 
         ds = getattr(data_source, "ds", None)
         if ds is not None:
@@ -579,12 +598,6 @@ class OffAxisProjectionFixedResolutionBuffer(FixedResolutionBuffer):
     that supports off axis projections.  This calls the volume renderer.
     """
 
-    def __init__(self, data_source, bounds, buff_size, antialias=True, periodic=False):
-        self.data = {}
-        FixedResolutionBuffer.__init__(
-            self, data_source, bounds, buff_size, antialias, periodic
-        )
-
     def __getitem__(self, item):
         if item in self.data:
             return self.data[item]
@@ -631,10 +644,18 @@ class ParticleImageBuffer(FixedResolutionBuffer):
 
     """
 
-    def __init__(self, data_source, bounds, buff_size, antialias=True, periodic=False):
-        self.data = {}
-        FixedResolutionBuffer.__init__(
-            self, data_source, bounds, buff_size, antialias, periodic
+    def __init__(
+        self,
+        data_source,
+        bounds,
+        buff_size,
+        antialias=True,
+        periodic=False,
+        *,
+        filters=None,
+    ):
+        super().__init__(
+            data_source, bounds, buff_size, antialias, periodic, filters=filters
         )
 
         # set up the axis field names

yt/visualization/fixed_resolution_filters.py

@@ -7,9 +7,11 @@
 
 def apply_filter(f):
     @wraps(f)
-    def newfunc(*args, **kwargs):
-        args[0]._filters.append((f.__name__, (args, kwargs)))
-        return args[0]
+    def newfunc(frb, *args, **kwargs):
+        frb._filters.append((f.__name__, (args, kwargs)))
+        # Invalidate the data of the frb to force its regeneration
+        frb._data_valid = False
+        return frb
 
     return newfunc
 
@@ -50,20 +52,12 @@ def __init__(self, nbeam=30, sigma=2.0):
     def apply(self, buff):
         from yt.utilities.on_demand_imports import _scipy
 
-        hnbeam = self.nbeam // 2
-        sigma = self.sigma
-
-        l = np.linspace(-hnbeam, hnbeam, num=self.nbeam + 1)
-        x, y = np.meshgrid(l, l)
-        g2d = (1.0 / (sigma * np.sqrt(2.0 * np.pi))) * np.exp(
-            -((x / sigma) ** 2 + (y / sigma) ** 2) / (2 * sigma ** 2)
+        spl = _scipy.ndimage.gaussian_filter(
+            buff,
+            self.sigma,
+            truncate=self.nbeam / self.sigma,
         )
-        g2d /= g2d.max()
-
-        npm, nqm = np.shape(buff)
-        spl = _scipy.signal.convolve(buff, g2d)
-
-        return spl[hnbeam : npm + hnbeam, hnbeam : nqm + hnbeam]
+        return spl
 
 
 class FixedResolutionBufferWhiteNoiseFilter(FixedResolutionBufferFilter):

yt/visualization/plot_container.py

@@ -21,67 +21,20 @@
 from yt.utilities.definitions import formatted_length_unit_names
 from yt.utilities.exceptions import YTNotInsideNotebook
 
-from ._commons import DEFAULT_FONT_PROPERTIES, validate_image_name
+from ._commons import (
+    DEFAULT_FONT_PROPERTIES,
+    invalidate_data,
+    invalidate_figure,
+    invalidate_plot,
+    validate_image_name,
+    validate_plot,
+)
 
 latex_prefixes = {
     "u": r"\mu",
 }
 
 
-def invalidate_data(f):
-    @wraps(f)
-    def newfunc(*args, **kwargs):
-        rv = f(*args, **kwargs)
-        args[0]._data_valid = False
-        args[0]._plot_valid = False
-        return rv
-
-    return newfunc
-
-
-def invalidate_figure(f):
-    @wraps(f)
-    def newfunc(*args, **kwargs):
-        rv = f(*args, **kwargs)
-        for field in args[0].plots.keys():
-            args[0].plots[field].figure = None
-            args[0].plots[field].axes = None
-            args[0].plots[field].cax = None
-        args[0]._setup_plots()
-        return rv
-
-    return newfunc
-
-
-def invalidate_plot(f):
-    @wraps(f)
-    def newfunc(*args, **kwargs):
-        rv = f(*args, **kwargs)
-        args[0]._plot_valid = False
-        return rv
-
-    return newfunc
-
-
-def validate_plot(f):
-    @wraps(f)
-    def newfunc(*args, **kwargs):
-        if hasattr(args[0], "_data_valid"):
-            if not args[0]._data_valid:
-                args[0]._recreate_frb()
-        if hasattr(args[0], "_profile_valid"):
-            if not args[0]._profile_valid:
-                args[0]._recreate_profile()
-        if not args[0]._plot_valid:
-            # it is the responsibility of _setup_plots to
-            # call args[0].run_callbacks()
-            args[0]._setup_plots()
-        rv = f(*args, **kwargs)
-        return rv
-
-    return newfunc
-
-
 def apply_callback(f):
     @wraps(f)
     def newfunc(*args, **kwargs):
@@ -373,6 +326,7 @@ def _initialize_dataset(self, ts):
             ts = DatasetSeries(ts)
         return ts
 
+    @invalidate_data
     def _switch_ds(self, new_ds, data_source=None):
         old_object = self.data_source
         name = old_object._type_name
@@ -399,7 +353,6 @@ def _switch_ds(self, new_ds, data_source=None):
             new_object = getattr(new_ds, name)(**kwargs)
 
         self.data_source = new_object
-        self._data_valid = self._plot_valid = False
 
         for d in "xyz":
             lim_name = d + "lim"