[plotter] add particle scatter overlay

plotter.py

@@ -689,6 +689,32 @@ class Plotter(Aggregator, BaseProcessor):
             **kwargs,
         )
 
+    def _overlay_particles(self, ax_los, im_extent, **kwargs):
+        """
+        Add an overlay with particles data
+        """
+
+        # Open particle HDF5 file
+        filename = self.save.get_node("/hdf5/particles").read()
+        hdf5_parts = tables.open(filename, "r")
+        part_pos = hdf5_parts.get_node("/data/pos").read()
+
+        # index of the horizontal axis
+        ih = self._ax_nb[self._axes_h[ax_los]]
+        # index of the vertical axis
+        iv = self._ax_nb[self._axes_v[ax_los]]
+
+        # horizontal coordinates
+        part_h = part_pos[:, ih]
+        part_v = part_pos[:, iv]
+
+        # Renormalize
+        part_h = im_extent[0] + (im_extent[1] - im_extent[0]) * part_h
+        part_v = im_extent[2] + (im_extent[3] - im_extent[2]) * part_v
+
+        # Scatter plot
+        plt.scatter(part_h, part_v)
+
     def _overlay_speed(
         self, ax_los, im_extent, unit=U.km_s, unit_coeff=1.0, key_v=None, **kwargs
     ):
@@ -1739,6 +1765,7 @@ class Plotter(Aggregator, BaseProcessor):
             "speed": self._overlay_speed,
             "levels": self._overlay_levels,
             "contour": self._overlay_contour,
+            "particles": self._overlay_particles,
         }
 
         super(Plotter, self).def_rules()