How to export ParaView colormap into a format that could be read by matplotlib?

ParaView Support
#1

I’m wondering is it possible to export ParaView colormap in RGB format to be able to read it in matplotlib? I know that ParaView could export colormaps in .json format but I don’t know how to convert it in a suitable format to be able to read it by using matplotlib.colors.ListedColormap function. Any idea or help is appreciated.

#2

Sure, here is a little function that can export the color map in a table:

def ExportPreset(lutName):
  from paraview import servermanager
  presets = paraview.servermanager.vtkSMTransferFunctionPresets()

  lut = GetColorTransferFunction('dummy')
  lut.ApplyPreset(lutName)

  import vtk
  helper = vtk.vtkUnsignedCharArray()

  dctf = lut.GetClientSideObject()
  dataRange = dctf.GetRange()

  for i in range(0, 256):
    x = (i/255.0) * (dataRange[1]-dataRange[0]) + dataRange[0]
    helper.SetVoidArray(dctf.MapValue(x), 3, 1)
    r = helper.GetValue(0)
    g = helper.GetValue(1)
    b = helper.GetValue(2)
    print("%d %d %d" % (r, g, b))

lutName is a string with the name of the colormap you’d like to export.

Evaluate and call this function in the Python Shell (View -> Python Shell). You can adapt the script to produce the type of array needed for the matplotlib function.

2 Likes
#3

Thanks Cory, it worked smoothly!