Added support for RGB plots (#137)

hvplot/__init__.py

@@ -523,6 +523,28 @@ def image(self, x=None, y=None, z=None, colorbar=True, **kwds):
         """
         return self(x, y, z=z, kind='image', colorbar=colorbar, **kwds)
 
+    def rgb(self, x=None, y=None, z=None, bands=None, **kwds):
+        """
+        RGB plot
+
+        Parameters
+        ----------
+        x, y : string, optional
+            The coordinate variable along the x- and y-axis
+        bands : string, optional
+            The coordinate variable to draw the RGB channels from
+        z : string, optional
+            The data variable to plot
+        **kwds : optional
+            Keyword arguments to pass on to
+            :py:meth:`hvplot.converter.HoloViewsConverter`.
+        Returns
+        -------
+        obj : HoloViews object
+            The HoloViews representation of the plot.
+        """
+        return self(x, y, z=z, bands=bands, kind='rgb', **kwds)
+
     def quadmesh(self, x=None, y=None, z=None, colorbar=True, **kwds):
         """
         QuadMesh plot

hvplot/converter.py

@@ -18,7 +18,7 @@
 from holoviews.element import (
     Curve, Scatter, Area, Bars, BoxWhisker, Dataset, Distribution,
     Table, HeatMap, Image, HexTiles, QuadMesh, Bivariate, Histogram,
-    Violin, Contours, Polygons, Points, Path, Labels
+    Violin, Contours, Polygons, Points, Path, Labels, RGB
 )
 from holoviews.plotting.util import process_cmap
 from holoviews.operation import histogram
@@ -147,7 +147,7 @@ class HoloViewsConverter(object):
         Declares a minimum sampling density beyond.
     """
 
-    _gridded_types = ['image', 'contour', 'contourf', 'quadmesh']
+    _gridded_types = ['image', 'contour', 'contourf', 'quadmesh', 'rgb']
 
     _geom_types = ['paths', 'polygons']
 
@@ -178,6 +178,7 @@ class HoloViewsConverter(object):
         'dataset'  : ['columns'],
         'table'    : ['columns'],
         'image'    : ['z', 'logz'],
+        'rgb'      : ['z', 'bands'],
         'quadmesh' : ['z', 'logz'],
         'contour'  : ['z', 'levels', 'logz'],
         'contourf' : ['z', 'levels', 'logz'],
@@ -193,7 +194,7 @@ class HoloViewsConverter(object):
         'kde': Distribution, 'area': Area, 'box': BoxWhisker, 'violin': Violin,
         'bar': Bars, 'barh': Bars, 'contour': Contours, 'contourf': Polygons,
         'points': Points, 'polygons': Polygons, 'paths': Path, 'step': Curve,
-        'labels': Labels
+        'labels': Labels, 'rgb': RGB
     }
 
     _colorbar_types = ['image', 'hexbin', 'heatmap', 'quadmesh', 'bivariate',
@@ -452,7 +453,10 @@ def _process_data(self, kind, data, x, y, by, groupby, row, col,
             dims = [c for c in data.coords if data[c].shape != ()
                     and c not in ignore]
             if kind is None and (not (x or y) or all(c in data.coords for c in (x, y))):
-                if len(dims) == 1:
+                if list(data.coords) == ['band', 'y', 'x']:
+                    kind = 'rgb'
+                    gridded = True
+                elif len(dims) == 1:
                     kind = 'line'
                 elif len(dims) == 2 or (x and y):
                     kind = 'image'
@@ -468,7 +472,7 @@ def _process_data(self, kind, data, x, y, by, groupby, row, col,
                                                              use_dask, persist, gridded,
                                                              label, value_label)
 
-            if kind not in self._stats_types:
+            if kind not in self._stats_types and kind != 'rgb':
                 if by is None: by = by_new
                 if groupby is None: groupby = groupby_new
 
@@ -1106,6 +1110,35 @@ def image(self, x=None, y=None, z=None, data=None):
         if self.geo: params['crs'] = self.crs
         return element(data, [x, y], z, **params).redim(**self._redim).redim.range(**ranges).opts(**opts)
 
+    def rgb(self, x=None, y=None, bands=None, data=None):
+        data = self.data if data is None else data
+
+        coords = list(data.coords)
+        if len(coords) < 3:
+            raise ValueError('Data must be 3D array to be converted to RGB.')
+        x = x or coords[2]
+        y = y or coords[1]
+        bands = bands or coords[0]
+        z = self.kwds.get('z', list(data.data_vars)[0])
+        nbands = len(data.coords[bands])
+        if nbands < 3:
+            raise ValueError('Selected bands coordinate (%s) has only %d channels,'
+                             'expected at least three channels to convert to RGB.' %
+                             (bands, nbands))
+        data = data[z]
+
+        params = dict(self._relabel)
+        opts = dict(plot=self._plot_opts, style=self._style_opts, norm=self._norm_opts)
+        if self.geo: params['crs'] = self.crs
+        xres, yres = data.attrs['res'] if 'res' in data.attrs else (1, 1)
+        xs = data.coords[x][::-1] if xres < 0 else data.coords[x]
+        ys = data.coords[y][::-1] if yres < 0 else data.coords[y]
+        eldata = (xs, ys)
+        for b in range(nbands):
+            eldata += (data[b].values,)
+        rgb = RGB(eldata, [x, y], RGB.vdims[:nbands], **params)
+        return rgb.redim(**self._redim).opts(**opts)
+
     def quadmesh(self, x=None, y=None, z=None, data=None):
         import xarray as xr
         data = self.data if data is None else data