# What is the function to extract colormap from volume data?
**URL:** https://discourse.vtk.org/t/what-is-the-function-to-extract-colormap-from-volume-data/1721
**Category:** Support
**Created:** [September 9, 2019, 2:02am UTC](https://discourse.vtk.org/t/what-is-the-function-to-extract-colormap-from-volume-data/1721 "2019-09-09T02:02:18Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@rjsgml5698](https://discourse.vtk.org/u/rjsgml5698)
#### Post date: [September 9, 2019, 2:02am UTC](https://discourse.vtk.org/t/what-is-the-function-to-extract-colormap-from-volume-data/1721/1 "2019-09-09T02:02:18Z")
Hello. I have two questions.
language : python
1. Does SetExtractionModeToLargestRegion () not apply to imagedata? only polydata?
2. What is the function to extract colormap from volume data?
Thank you
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### Author:  [@lassoan](https://discourse.vtk.org/u/lassoan)
#### Post date: [September 9, 2019, 3:05am UTC](https://discourse.vtk.org/t/what-is-the-function-to-extract-colormap-from-volume-data/1721/2 "2019-09-09T03:05:50Z")
> [@rjsgml5698](#):
>
> Does SetExtractionModeToLargestRegion () not apply to imagedata? only polydata?
Which filter are you using?
> [@rjsgml5698](#):
>
> What is the function to extract colormap from volume data?
Colormap is not “volume data” and not stored in “volume data”. Color map is stored in a [vtkScalarsToColors](https://vtk.org/doc/nightly/html/classvtkScalarsToColors.html)-derived class.
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### Author:  [@rjsgml5698](https://discourse.vtk.org/u/rjsgml5698)
#### Post date: [September 9, 2019, 4:36am UTC](https://discourse.vtk.org/t/what-is-the-function-to-extract-colormap-from-volume-data/1721/4 "2019-09-09T04:36:05Z")
Thank you for answer.
I converted png to vti (vtkimagedata).
And I want to share png’s colormap with vti (vtkimagedata). This is because I want to see the color of png in vti. Is there a simple example for this? Or is there a conceptual way?
Please understand my lack of English.
Thanks.
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### Author:  [@Sebastien\_Jourdain](https://discourse.vtk.org/u/Sebastien_Jourdain)
#### Post date: [September 9, 2019, 4:53pm UTC](https://discourse.vtk.org/t/what-is-the-function-to-extract-colormap-from-volume-data/1721/5 "2019-09-09T16:53:51Z")
Just letting the mapper know to don’t interpret the values as scalars. That way the raw value will be used as is without applying a LookupTable to convert a number into a color since you already have the color encoded.
>
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### Author:  [@rjsgml5698](https://discourse.vtk.org/u/rjsgml5698)
#### Post date: [September 10, 2019, 5:32am UTC](https://discourse.vtk.org/t/what-is-the-function-to-extract-colormap-from-volume-data/1721/6 "2019-09-10T05:32:10Z")
> [@Sebastien\_Jourdain](#):
>
> vtkMapper.h
Is there a way for vtkVolumeMapper not to interpret values as scalars?
There seems to be no ColorMode.
Thank you for always.
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### Author:  [@cory.quammen](https://discourse.vtk.org/u/cory.quammen)
#### Post date: [September 10, 2019, 2:29pm UTC](https://discourse.vtk.org/t/what-is-the-function-to-extract-colormap-from-volume-data/1721/7 "2019-09-10T14:29:32Z")
> [@rjsgml5698](#):
>
> Is there a way for vtkVolumeMapper not to interpret values as scalars?
This may help: [VTK: vtkVolumeProperty Class Reference](https://vtk.org/doc/nightly/html/classvtkVolumeProperty.html#a2534a6dc500be42c9a842d405c4ee0bb)
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### Author:  [@dgobbi](https://discourse.vtk.org/u/dgobbi)
#### Post date: [September 10, 2019, 10:30pm UTC](https://discourse.vtk.org/t/what-is-the-function-to-extract-colormap-from-volume-data/1721/8 "2019-09-10T22:30:05Z")
> [@rjsgml5698](#):
>
> - oes SetExtractionModeToLargestRegion () not apply to imagedata? only polydata?
Use [vtkImageConnectivityFilter](https://vtk.org/doc/nightly/html/classvtkImageConnectivityFilter.html) or [vtkImageThresholdConnectivity](https://vtk.org/doc/nightly/html/classvtkImageThresholdConnectivity.html).