Update Colorizer/ColorizingArtist to work with MultiNorm (matplotlib#30511)

Update Colorizer/ColorizingArtist to work with MultiNorm
improved testing for colorizer+multinorm

Author: trygvrad

lib/matplotlib/cbook.py

@@ -694,7 +694,21 @@ def safe_masked_invalid(x, copy=False):
     try:
         xm = np.ma.masked_where(~(np.isfinite(x)), x, copy=False)
     except TypeError:
-        return x
+        if len(x.dtype.descr) == 1:
+            # Arrays with dtype 'object' get returned here.
+            # For example the 'c' kwarg of scatter, which supports multiple types.
+            # `plt.scatter([3, 4], [2, 5], c=[(1, 0, 0), 'y'])`
+            return x
+        else:
+            # In case of a dtype with multiple fields
+            # for example image data using a MultiNorm
+            try:
+                mask = np.empty(x.shape, dtype=np.dtype('bool, '*len(x.dtype.descr)))
+                for dd, dm in zip(x.dtype.descr, mask.dtype.descr):
+                    mask[dm[0]] = ~np.isfinite(x[dd[0]])
+                xm = np.ma.array(x, mask=mask, copy=False)
+            except TypeError:
+                return x
     return xm
 
 

lib/matplotlib/cm.py

@@ -239,32 +239,3 @@ def get_cmap(self, cmap):
 _multivar_colormaps = ColormapRegistry(multivar_cmaps)
 
 _bivar_colormaps = ColormapRegistry(bivar_cmaps)
-
-
-def _ensure_cmap(cmap):
-    """
-    Ensure that we have a `.Colormap` object.
-
-    For internal use to preserve type stability of errors.
-
-    Parameters
-    ----------
-    cmap : None, str, Colormap
-
-        - if a `Colormap`, return it
-        - if a string, look it up in mpl.colormaps
-        - if None, look up the default color map in mpl.colormaps
-
-    Returns
-    -------
-    Colormap
-
-    """
-    if isinstance(cmap, colors.Colormap):
-        return cmap
-    cmap_name = mpl._val_or_rc(cmap, "image.cmap")
-    # use check_in_list to ensure type stability of the exception raised by
-    # the internal usage of this (ValueError vs KeyError)
-    if cmap_name not in _colormaps:
-        _api.check_in_list(sorted(_colormaps), cmap=cmap_name)
-    return mpl.colormaps[cmap_name]