Choosing color_mapper using Select

I want to be able to change the palette using select.
Below is an example of my attempt. I just want to change the palette by taking the values out of the box.

import numpy as np
from bokeh.plotting import figure, show
from bokeh.models import Row
from bokeh.models import LinearColorMapper, BasicTicker, ColorBar, Select,CustomJS
from bokeh.models.widgets import RangeSlider
import bokeh
data = np.random.rand(10,10)
select = Select(title="Palette:", options=["Viridis256","Magma256"])
color_mapper = LinearColorMapper(palette=select.options[0], low=0, high=1)

figure = figure(x_range=(0,1), y_range=(0,1))
img = figure.image(image=[data], color_mapper=color_mapper,
                   dh=[1.0], dw=[1.0], x=[0], y=[0])

color_bar = ColorBar(color_mapper=color_mapper, ticker= BasicTicker(),
                     location=(0,0))

figure.add_layout(color_bar, 'right')
cmap_callback = CustomJS(args=dict(img=img), code='''
                        img.glyph.color_mapper.palette=this.value;
                        ''')
select.js_on_change( 'value',cmap_callback)
show(Row(figure, select ))

image926×612 19.6 KB

However, the selection doesn’t work. The console displays the following:

I do not understand what the problem is, because I’m passing exactly what he considers invalid. Most likely the problem is in js. I have no proper experience with this language.

@KonradCurze The problem is that the ability to configure the palettes by string names is merely a convenience, and one that only exists on the Python side. The actual real type of the palette property is a list of colors. So if you are setting the property from JS you will need to assign values that are lists of colors that comprise the palette, instead of strings.

import numpy as np
from bokeh.plotting import figure, show
from bokeh.models import Row
from bokeh.models import LinearColorMapper, BasicTicker, ColorBar, Select,CustomJS
from bokeh.io import output_notebook
import bokeh

output_notebook()

colormaps = ['Cividis', 'Magma', 'Inferno', 'Plasma', 'Viridis', 'RdBu', 'Spectral', 'RdYlBu']
bokeh_maps = {k: list(eval('bokeh.palettes.{}'.format(k)).values())[-1] for k in colormaps}###### This is where the main change is located

data = np.random.rand(25,25)

figure = figure(x_range=(0,1), y_range=(0,1))

color_mapper = bokeh.models.LinearColorMapper(palette=bokeh_maps[colormaps[0]], low=0, high=1)
color_bar = bokeh.models.ColorBar(color_mapper=color_mapper, location=(0,0))
figure.add_layout(color_bar, 'right')

select = bokeh.models.Select(title='Palette:', options=colormaps, value=colormaps[0])

img = figure.image(image=[data], color_mapper=color_mapper,
                   dh=[1.0], dw=[1.0], x=[0], y=[0])

cmap_callback = CustomJS(args=dict(
                        bokeh_maps=bokeh_maps,
                        color_bar=color_bar,
                        ),
                        code="""
                        color_bar.color_mapper.palette = bokeh_maps[cb_obj.value]
                        """)
select.js_on_change('value',cmap_callback)
show(Row(figure, select ))