# transform RGBA to RGB after blending

**URL:** https://discourse.vtk.org/t/transform-rgba-to-rgb-after-blending/2576
**Category:** Support
**Created:** [February 10, 2020, 4:35pm UTC](https://discourse.vtk.org/t/transform-rgba-to-rgb-after-blending/2576 "2020-02-10T16:35:42Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![rprueckl](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/r/c37758/32.png) [@rprueckl](https://discourse.vtk.org/u/rprueckl)
#### Post date: [February 10, 2020, 4:35pm UTC](https://discourse.vtk.org/t/transform-rgba-to-rgb-after-blending/2576/1 "2020-02-10T16:35:42Z")

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I want to achieve a fairly simple operation in VTK. My starting point are several 2D images (same dimensions) that I want blend together over a black background. All images have alpha channels and some (semi)transparent areas. After blending, I want to remove the alpha channel to get an image without transparencies (i.e. a pixel that would have been fully transparent in all source images would would result in an opaque black pixel).  
After googling a lot I still have no idea how to achieve that. Any advice is welcome. Thanks in advance.