[vtk-developers] Interesting problem building a vtkLookupTable from vtkColorSeries.

[David Thompson]

Hi Andrew,

Have you tried IndexedLookupOff, i.e.

   lut = vtk.vtkLookupTable()
   colorSeries.BuildLookupTable(lut)
   lut.IndexedLookupOff()

on the first lookup table?

    David

On Jul 20, 2014, at 1:21, Andrew Maclean <andrew.amaclean at gmail.com> wrote:

> I wanted to generate a lookup table from vtkCOlor series using BuildLookupTable().
> However the only way I can do it is to create a second lookup table and copy from the first to the second one.
> I thought I could do this:
>     colorSeries = vtk.vtkColorSeries()
>     colorSeriesEnum = colorSeries.BREWER_DIVERGING_BROWN_BLUE_GREEN_10
>     colorSeries.SetColorScheme(colorSeriesEnum)
>     lut = vtk.vtkLookupTable()
>     colorSeries.BuildLookupTable(lut)
> 
> But I have to do this:
>     colorSeries = vtk.vtkColorSeries()
>     colorSeriesEnum = colorSeries.BREWER_DIVERGING_BROWN_BLUE_GREEN_10
>     colorSeries.SetColorScheme(colorSeriesEnum)
>     lut1 = vtk.vtkLookupTable()
>     colorSeries.BuildLookupTable(lut1)
>     lut = vtk.vtkLookupTable()
>     lut.SetNumberOfTableValues(lut1.GetNumberOfTableValues())
>     for i in range(0,lut1.GetNumberOfTableValues()):
>         lut.SetTableValue(i,lut1.GetTableValue(i))
> 
> In looking at the code in vtkColorSeries.cxx, namely:
> //-----------------------------------------------------------------------------
> void vtkColorSeries::BuildLookupTable(vtkLookupTable* lkup)
> {
>   if (lkup)
>     {
>     lkup->SetNumberOfTableValues(this->GetNumberOfColors());
>     lkup->IndexedLookupOn();
>     for (int i = 0; i < this->GetNumberOfColors(); ++i)
>       {
>       vtkColor3ub colr = this->GetColor(i);
>       lkup->SetTableValue(
>         i, colr.GetRed()/255., colr.GetGreen()/255., colr.GetBlue()/255., 1.);
>       }
>     }
> }
> It seems lkup is built correctly.
> 
> I can't see any reason for building and then copying to a new table.
> 
> I would appreciate it if anyone could point out what I am missing.
> 
> I have also attached a Python script that illustrates this.
> 
> Regards
>    Andrew
> -- 
> ___________________________________________
> Andrew J. P. Maclean
> 
> ___________________________________________
> <ColorSeries.zip>
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