[vtkusers] simple vtkLookupTable question

[Cory Quammen]

Richard,

It's actually a little bit involved.

Here's Python code to generate ParaView's Black-Body Radiation color map,
which I think is similar to ImageJ's 'hot' lookup table.

import vtk

cmap = vtk.vtkDiscretizableColorTransferFunction()
cmap.SetColorSpaceToRGB()
cmap.AddRGBPoint(0.0, 0.0, 0.0, 0.0) # black
cmap.AddRGBPoint(0.4, 1.0, 0.9, 0.0) # reddish
cmap.AddRGBPoint(0.8, 0.9, 0.9, 0.0) # yellow
cmap.AddRGBPoint(1.0, 1.0, 1.0, 1.0) # white

scalarValues = vtk.vtkFloatArray()
scalarValues.SetNumberOfComponents(1)
scalarValues.SetNumberOfTuples(256)
for i in xrange(256):
    scalarValues.SetTupleValue(i, [i / 255.0])

table = cmap.MapScalars(scalarValues, 0, -1)

for i in xrange(table.GetNumberOfTuples()):
    print table.GetTuple(i)

Note that this defines a colormap for scalar values in the range [0, 1].
You can rescale the first arguments to AddRGBPoints() above for a different
scalar range.

Hope that helps,
Cory

On Wed, Oct 21, 2015 at 5:22 AM, mbcx9rb9 <richard.j.brown at live.co.uk>
wrote:

> I imagine this is a very simple question, but I haven't found the answer
> already in the group.
>
> I have greyscale data that I want to apply a lookup table to. Currently, my
> lowest value is red and my highest is blue, but I would like something that
> looks more like the 'fire' lookup table in imageJ.
>
> In essence, I think I want my lowest value to be black and my highest to be
> a red/white. Can anyone give me any pointers?
>
> Thanks in advance,
> Richard Brown
>
>
>
> --
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-- 
Cory Quammen
R&D Engineer
Kitware, Inc.
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