# Slice display - why image in slicer is more smoothing

**URL:** <https://discourse.slicer.org/t/slice-display-why-image-in-slicer-is-more-smoothing/15259>\
**Category:** Support\
**Tags:** display\
**Created:** [December 29, 2020, 3:28am UTC](https://discourse.slicer.org/t/slice-display-why-image-in-slicer-is-more-smoothing/15259 "2020-12-29T03:28:07Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![czj1989](https://avatars.discourse-cdn.com/v4/letter/c/9e8a1a/32.png) [@czj1989](https://discourse.slicer.org/u/czj1989)\
**Post date:** [December 29, 2020, 3:28am UTC](https://discourse.slicer.org/t/slice-display-why-image-in-slicer-is-more-smoothing/15259/1 "2020-12-29T03:28:07Z")

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Hello! It is not a bug. I just wonder something about the slice display in Slicer. when I used vtk6.2 to display image with vtkImageReslice::SetInterpolationModeToLinear() and vtkImageActor:InterpolateOn(), I got Figure A which was not smoothing. But I load the same image in Slicer, then I got Figure B which was very smoothing. I tried to set output spacing of vtkImageReslice as 0.25 x original spacing, and then I got the result as slicer’s. However, I found it became slower when I paged down, and there was no this problem in slicer.

Can you tell me the additional operations has done by Slicer? Thank you very much!

Figure A  
 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/e/2/e25f7335fedfc5a078fd59262c56b4d0a053a4f2.jpeg)  
Figure B

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/b/7/b75ef5d25e5870e0de4793b65be31c95a3ac0672.jpeg)

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [December 29, 2020, 6:52pm UTC](https://discourse.slicer.org/t/slice-display-why-image-in-slicer-is-more-smoothing/15259/2 "2020-12-29T18:52:48Z")

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Answer from @pieper:

> Maybe the difference is that Slicer uses vtkImageReslice to resample the images to screen space (pixels on your monitor) but when you use a vtkImageActor it uses the original image as a texture.

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**Author:** ![czj1989](https://avatars.discourse-cdn.com/v4/letter/c/9e8a1a/32.png) [@czj1989](https://discourse.slicer.org/u/czj1989)\
**Post date:** [December 31, 2020, 9:12am UTC](https://discourse.slicer.org/t/slice-display-why-image-in-slicer-is-more-smoothing/15259/3 "2020-12-31T09:12:28Z")

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Thank you for answering my question. Does Slicer use ImageActor to display image or use other actor?

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [December 31, 2020, 5:33pm UTC](https://discourse.slicer.org/t/slice-display-why-image-in-slicer-is-more-smoothing/15259/4 "2020-12-31T17:33:59Z")

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vtkImageActor is good for simple use cases but we need many more features in 3D Slicer. Therefore, we prepare all data using VTK filter pipelines and render it by a simple actor and polydata mapper, displaying texture on a rectangle.

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**Author:** ![czj1989](https://avatars.discourse-cdn.com/v4/letter/c/9e8a1a/32.png) [@czj1989](https://discourse.slicer.org/u/czj1989)\
**Post date:** [January 4, 2021, 1:11am UTC](https://discourse.slicer.org/t/slice-display-why-image-in-slicer-is-more-smoothing/15259/5 "2021-01-04T01:11:05Z")

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Thank you very much! This is very useful for me. I wil try it.