Added support for static bokeh png rendering

.travis.yml

@@ -29,7 +29,7 @@ install:
   - conda info -a
   - conda create -q -n test-environment python=$TRAVIS_PYTHON_VERSION scipy=0.18.1 numpy freetype nose bokeh=0.12.5 pandas=0.19.2 jupyter ipython=4.2.0 param pyqt=4 matplotlib=1.5.1 xarray datashader dask=0.13
   - source activate test-environment
-  - conda install -c conda-forge  -c scitools iris sip=4.18 plotly flexx
+  - conda install -c conda-forge  iris sip=4.18 plotly flexx
   - if [[ "$TRAVIS_PYTHON_VERSION" == "3.4" ]]; then
       conda install python=3.4.3;
     fi

holoviews/plotting/bokeh/renderer.py

@@ -1,3 +1,5 @@
+from io import BytesIO
+
 import numpy as np
 import param
 from param.parameterized import bothmethod
@@ -25,7 +27,7 @@ class BokehRenderer(Renderer):
 
     backend = param.String(default='bokeh', doc="The backend name.")
 
-    fig = param.ObjectSelector(default='auto', objects=['html', 'json', 'auto'], doc="""
+    fig = param.ObjectSelector(default='auto', objects=['html', 'json', 'auto', 'png'], doc="""
         Output render format for static figures. If None, no figure
         rendering will occur. """)
 
@@ -42,7 +44,7 @@ class BokehRenderer(Renderer):
         bokeh server app. By default renders all output is rendered to HTML.""")
 
     # Defines the valid output formats for each mode.
-    mode_formats = {'fig': {'default': ['html', 'json', 'auto'],
+    mode_formats = {'fig': {'default': ['html', 'json', 'auto', 'png'],
                             'server': ['html', 'json', 'auto']},
                     'holomap': {'default': ['widgets', 'scrubber', 'auto', None],
                                 'server': ['server', 'auto', None]}}
@@ -75,6 +77,14 @@ def __call__(self, obj, fmt=None, doc=None):
             return self.server_doc(plot, doc), info
         elif isinstance(plot, tuple(self.widgets.values())):
             return plot(), info
+        elif fmt == 'png':
+            if bokeh_version < '0.12.6':
+                raise RuntimeError('Bokeh png export only supported by versions >=0.12.6.')
+            from bokeh.io import _get_screenshot_as_png
+            img = _get_screenshot_as_png(plot.state)
+            imgByteArr = BytesIO()
+            img.save(imgByteArr, format='PNG')
+            return imgByteArr.getvalue(), info
         elif fmt == 'html':
             html = self.figure_data(plot, doc=doc)
             html = "<div style='display: table; margin: 0 auto;'>%s</div>" % html

tests/testrenderclass.py

@@ -9,7 +9,7 @@
 from nose.plugins.attrib import attr
 import numpy as np
 
-from holoviews import HoloMap, Image, ItemTable, Store, GridSpace, Table
+from holoviews import HoloMap, Image, ItemTable, Store, GridSpace, Table, Curve
 from holoviews.element.comparison import ComparisonTestCase
 from holoviews.plotting import Renderer
 
@@ -23,6 +23,7 @@
 
 try:
     from holoviews.plotting.bokeh import BokehRenderer
+    from holoviews.plotting.bokeh.util import bokeh_version
 except:
     pass
 
@@ -146,3 +147,12 @@ def test_get_size_tables_in_layout(self):
         plot = self.renderer.get_plot(table+table)
         w, h = self.renderer.get_size(plot)
         self.assertEqual((w, h), (680, 300))
+
+    def test_render_to_png(self):
+        if bokeh_version < str('0.12.6'):
+            raise SkipTest('Bokeh static png rendering requires bokeh>=0.12.6')
+        curve = Curve([])
+        renderer = BokehRenderer.instance(fig='png')
+        png, info = renderer(curve)
+        self.assertIsInstance(png, bytes)
+        self.assertEqual(info['file-ext'], 'png')