# VTK error with vector images

**URL:** <https://discourse.slicer.org/t/vtk-error-with-vector-images/41071>\
**Category:** Support\
**Created:** [January 14, 2025, 6:37am UTC](https://discourse.slicer.org/t/vtk-error-with-vector-images/41071 "2025-01-14T06:37:07Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![muratmaga](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/muratmaga/32/3622_2.png) [@muratmaga](https://discourse.slicer.org/u/muratmaga)\
**Post date:** [January 14, 2025, 6:37am UTC](https://discourse.slicer.org/t/vtk-error-with-vector-images/41071/1 "2025-01-14T06:37:08Z")

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When I try to set a vector image as a background volume and a scalar image as as a background volume, I get this error and slice view is messed up:  
`[VTK] The first input can have a maximum of four components`

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/0/6/06277dd72813b570dfaa34d7b511509f12572976.png)

The other way around works fine:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/d/0/d034474665a7e621f5e725f33d67bf5a58b2696e.jpeg)

Is this a bug?  
@lassoan @pieper

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**Author:** ![muratmaga](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/muratmaga/32/3622_2.png) [@muratmaga](https://discourse.slicer.org/u/muratmaga)\
**Post date:** [January 14, 2025, 6:41am UTC](https://discourse.slicer.org/t/vtk-error-with-vector-images/41071/2 "2025-01-14T06:41:49Z")

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Looking at this thread, this appears to be a know issue:

> [@RGB or RGBA rendering of single 2D image in 3D not working](https://discourse.slicer.org/t/rgb-or-rgba-rendering-of-single-2d-image-in-3d-not-working/16649/2):
>
> 3-component RGB images appear correctly in slice views and the slices can be displayed in 3D view, too. 4-component RGBA images are required for color volume rendering but RGBA volumes, but slice views of such volumes cannot be displayed in 3D view - see [this issue](https://github.com/Slicer/Slicer/issues/4939). If you want this to be fixed then [add a vote for it](https://discourse.slicer.org/t/about-the-feature-requests-category/30). If an issue gets many quotes (or needed for a funded project) then we can allocate developers to fix it. If you need it sooner and you are comfortable with C++ and the VTK library…

In that case, is there a way to convert RGBA image into RGB in Slicer?

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [January 14, 2025, 8:44pm UTC](https://discourse.slicer.org/t/vtk-error-with-vector-images/41071/3 "2025-01-14T20:44:24Z")

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> [@muratmaga](#):
>
> In that case, is there a way to convert RGBA image into RGB in Slicer?

With a couple lines of python you can strip away the alpha channel and then make a new volume. I don’t think we have a module that does it though.

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**Author:** ![muratmaga](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/muratmaga/32/3622_2.png) [@muratmaga](https://discourse.slicer.org/u/muratmaga)\
**Post date:** [January 14, 2025, 8:55pm UTC](https://discourse.slicer.org/t/vtk-error-with-vector-images/41071/4 "2025-01-14T20:55:26Z")

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I actually managed that last night, but that turned out to be a dead end too.

It appears I cannot use the transparency and overlays with RGB images in slice views (I presume due to lack of alpha channel, unless it is a bug).

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [January 14, 2025, 9:19pm UTC](https://discourse.slicer.org/t/vtk-error-with-vector-images/41071/5 "2025-01-14T21:19:50Z")

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Color image rendering hasn’t been much of a priority, but yes, it should be possible to fix the pipelines if someone is able to dig into it.