# Volume rendering with vtkVolumeRayCastMapper but need help extracting the rendered grayscale image.

**URL:** https://discourse.vtk.org/t/volume-rendering-with-vtkvolumeraycastmapper-but-need-help-extracting-the-rendered-grayscale-image/2404
**Category:** Support
**Created:** [January 11, 2020, 3:13am UTC](https://discourse.vtk.org/t/volume-rendering-with-vtkvolumeraycastmapper-but-need-help-extracting-the-rendered-grayscale-image/2404 "2020-01-11T03:13:33Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![spencermanwell](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/s/eada6e/32.png) [@spencermanwell](https://discourse.vtk.org/u/spencermanwell)
#### Post date: [January 11, 2020, 3:13am UTC](https://discourse.vtk.org/t/volume-rendering-with-vtkvolumeraycastmapper-but-need-help-extracting-the-rendered-grayscale-image/2404/1 "2020-01-11T03:13:33Z")

</div>

Hello VTK,

I have been rendering volumes using vtkVolumeRayCastMapper with a modified vtkVolumeRayCastMIPFunction as grayscale images and I am interested in extracting the pixel values of these and writing the images to file. In the following thread,

[http://vtk.1045678.n5.nabble.com/How-to-get-the-pixels-of-a-volume-rendered-image-td5742531.html](http://vtk.1045678.n5.nabble.com/How-to-get-the-pixels-of-a-volume-rendered-image-td5742531.html)

this task was performed (seemingly) easily using methods of the vtkGPUVolumeRayCastMapper, e.g. GetColorImage() or GetDepthImage(). As no similar methods exist for the vtkVolumeRayCastMapper class, I am not sure of the best way to proceed. It’s probably worth noting that I am currently working with vtk5.6.

Helpful suggestions would be greatly appreciated.

Best regards,  
Spencer