[vtkusers] Medical image display - color of image pixels outside an image volume sliced with vtkImageResliceMapper

[David Gobbi]

Hi Andrea,

I've tried reproducing your problem with CTs on my own system, but so far I
haven't seen the grey border.

Can you show me all of the settings that you use with vtkImageResliceMapper
and also all the settings for the vtkImageProperty?

Also, can you tell me what version of VTK you are using?  And whether
you're using the OpenGL backend or the OpenGL2 backend?

And what your are using to read the DICOM images into your program (ITK,
vtkDICOMImageReader, vtk-dicom, GDCM, etc)?

 - David



On Thu, May 3, 2018 at 3:14 PM, Andrea Borsic <aborsic at ne-scientific.com>
wrote:

> Hi,
>
> I have a question about the use of the vtkImageReslice mapper.
>
> In setting up a VTK pipeline for displaying CT image slices we used
> previously a vtkImageReslice followed by a vtkImageMapToColors. We have
> recently switched to using a vtkImageResliceMapper instead of the two
> previous classes, but we are experiencing an issue.
>
> When using vtkImageReslice the method SetBackgroundLevel() was called with
> a value of -1000 which mapped pixels falling outside the sampled CT volume
> to a black pixel on screen, given the LUT in use.
>
> In vtkImageResliceMapper the conversion from CT scalar values to screen
> colors is performed internally and we have tried playing with
> BackgroundOn() and with SetBackingColor of a vtkImagePorperty is passed to
> the vtkImageResliceMapper, but we are not able to get rid of a thin gray
> border that at times shows around the image as shown in the screenshot
> below ....
>
>
>
> Additionally, when the slicing plane is set at the very beginning of the
> volume or at the very end, the output is a slice which is completely gray.
>
> I suspect that pixel values for sampling locations that fall outside of
> the CT image volume are set to a default value which results in the gray
> pixels.
>
> Can anyone please advise on how to control such value - so that gray
> borders could be eliminated?
>
> Thanks in advance for any suggestion,
>
> Best Regards,
>
> Andrea
>
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