SVG Support for Bokeh Backend

I wrote this a while back for HoloExt; was wondering if there’s any interest for me to make a PR for this?

import os
from bokeh import models
from bokeh.io import export_svgs
from holoext.utils import DEFAULT_N, get_cmap, flatten, tidy_fn

def _get_figures_core(objs):
    if isinstance(objs, list):
        objs = [_get_figures_core(plot) for plot in objs]
    elif isinstance(objs, (models.Column, models.Row)):
        objs = [_get_figures_core(child) for child in objs.children
                if not isinstance(child, (models.ToolbarBox,
                                          models.WidgetBox))]
    return objs

def _get_figures(objs):
    try:
        return list(flatten(_get_figures_core(objs)))
    except TypeError:
        return [_get_figures_core(objs)]

def _save_to_svg(hv_obj, save):
    bokeh_obj = hv.renderer('bokeh').get_plot(hv_obj).state
    figures = _get_figures(bokeh_obj)
    for i, figure in enumerate(figures):
        figure.output_backend = 'svg'

        if len(figures) != 1:
            if not os.path.exists(save):
                os.mkdir(save)
            tidied_title = tidy_fn(figure.title.text)
            save_fp = os.path.join(
                save, '{0}_{1}'.format(tidied_title, i))
        else:
            save_fp = save

        if not save_fp.endswith('svg'):
            save_fp = '{0}.{1}'.format(save_fp, 'svg')

        export_svgs(figure, save_fp)

import numpy as np
import holoviews as hv
hv.extension('bokeh')

frequencies = [0.5, 0.75, 1.0, 1.25]

def sine_curve(phase, freq):
    xvals = [0.1* i for i in range(100)]
    return hv.Curve((xvals, [np.sin(phase+freq*x) for x in xvals]))

curve_dict = {f:sine_curve(0,f) for f in frequencies}

NdLayout = hv.NdLayout(curve_dict, kdims='frequency')
_save_to_svg(NdLayout, 'ndlayout_svgs')

[RColetto]

Hi guys, I think I’m missing something. I generated from Holoviews some graphs (Scatterplot, Violinplot) and managed to save all of them in svg format, using the following code:

#set the backend and the renderer
hv.extension('bokeh')
br = hv.renderer('bokeh')

#set the data
np.random.seed(37)
groups = [chr(65+g) for g in np.random.randint(0, 3, 200)]

#plot 
violin = hv.Violin((groups, np.random.randint(0, 5, 200), np.random.randn(200)),
          ['Group', 'Category'], 'Value')

#export the plot
plot = br.get_plot(violin )
plot = plot.state
plot.output_backend='svg'
export_svgs(plot, filename="Violin.svg")

It seems to work properly, so I can’t understand why Bokeh’s guide (https://bokeh.pydata.org/en/latest/docs/user_guide/compat.html) and the code behind Bokeh’s renderer in Holoviews state it is not possible doing this (i.e. exporting to svg format using Bokeh backend, while it is possible from matplotlib). Is there any limitation I can’t see that is preventing this function to be included in Holoviews?

[Sieboldianus]

As of Bokeh 0.12.6 it is also possible to export to SVG directly from python. I found this solution pretty straight forward:

from bokeh.io import export_svgs
p =  hv.render(heatmap, backend='bokeh')
p.output_backend = "svg"
export_svgs(p, filename="heatmap.svg")