custom matplotlib colormap and convert to vtk colormap

BrYlBu.py

_BrBG_data = (
    (0.32941176470588235,  0.18823529411764706,  0.0196078431372549 ),
    (0.5490196078431373 ,  0.31764705882352939,  0.0392156862745098 ),
    (0.74901960784313726,  0.50588235294117645,  0.17647058823529413),
    (0.87450980392156863,  0.76078431372549016,  0.49019607843137253),
    (0.96470588235294119,  0.90980392156862744,  0.76470588235294112),
    (0.96078431372549022,  0.96078431372549022,  0.96078431372549022),
    (0.7803921568627451 ,  0.91764705882352937,  0.89803921568627454),
    (0.50196078431372548,  0.80392156862745101,  0.75686274509803919),
    (0.20784313725490197,  0.59215686274509804,  0.5607843137254902 ),
    (0.00392156862745098,  0.4                ,  0.36862745098039218),
    (0.0                ,  0.23529411764705882,  0.18823529411764706)
    )
_RdYlBu_data = (
    (0.6470588235294118 , 0.0                 , 0.14901960784313725),
    (0.84313725490196079, 0.18823529411764706 , 0.15294117647058825),
    (0.95686274509803926, 0.42745098039215684 , 0.2627450980392157 ),
    (0.99215686274509807, 0.68235294117647061 , 0.38039215686274508),
    (0.99607843137254903, 0.8784313725490196  , 0.56470588235294117),
    (1.0                , 1.0                 , 0.74901960784313726),
    (0.8784313725490196 , 0.95294117647058818 , 0.97254901960784312),
    (0.6705882352941176 , 0.85098039215686272 , 0.9137254901960784 ),
    (0.45490196078431372, 0.67843137254901964 , 0.81960784313725488),
    (0.27058823529411763, 0.45882352941176469 , 0.70588235294117652),
    (0.19215686274509805, 0.21176470588235294 , 0.58431372549019611)
    )

_BrYlBu_data = (
    (0.32941176470588235,  0.18823529411764706,  0.0196078431372549 ),
    (0.5490196078431373 ,  0.31764705882352939,  0.0392156862745098 ),
    (0.74901960784313726,  0.50588235294117645,  0.17647058823529413),
    (0.87450980392156863,  0.76078431372549016,  0.49019607843137253),
    (0.96470588235294119,  0.90980392156862744,  0.76470588235294112),
    (1.0                , 1.0                 , 0.74901960784313726),
    (0.8784313725490196 , 0.95294117647058818 , 0.97254901960784312),
    (0.6705882352941176 , 0.85098039215686272 , 0.9137254901960784 ),
    (0.45490196078431372, 0.67843137254901964 , 0.81960784313725488),
    (0.27058823529411763, 0.45882352941176469 , 0.70588235294117652),
    (0.19215686274509805, 0.21176470588235294 , 0.58431372549019611)
    )
MYCMAP = 'BrYlBu'

import numpy as np
import matplotlib.colors as colors
import matplotlib.pyplot as plt
from matplotlib import cm

mycmap_inst = colors.LinearSegmentedColormap.from_list(MYCMAP, _BrYlBu_data, cm.LUTSIZE)
cm.register_cmap(name=MYCMAP,cmap=mycmap_inst)

# Make plot with vertical (default) colorbar
fig, ax = plt.subplots()
d = [np.arange(0,1.1,0.1)]

mycmap_inst = cm.get_cmap(MYCMAP)
mycmap_inst.set_bad(color='white')
cax = ax.imshow(d, interpolation='nearest', cmap=mycmap_inst)
fig.colorbar(cax)
plt.savefig(MYCMAP+'.png')

#### convert to VTK colormap
import vtk
# scale 0,1 to 0,100 unsigned short     
vmax = 1
maxval = 100*vmax
scaleval = 100*vmax
cmap = cm.get_cmap(MYCMAP)
# Transfer Functions
opacity_tf = vtk.vtkPiecewiseFunction()
color_tf = vtk.vtkColorTransferFunction()
tf = []
for val in np.linspace(0,1,11):
    alpha = val*0.1
    r = cmap(val)[0]
    g = cmap(val)[1]
    b = cmap(val)[2]
    tf.append([val*maxval,alpha,r,g,b])

for p in tf:
    color_tf.AddRGBPoint(p[0], p[2], p[3], p[4])
    opacity_tf.AddPoint(p[0], p[1])