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

[Andrea Borsic]

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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