# how to Edit/add units per pixel to a Tiff stack?

**URL:** <https://discourse.slicer.org/t/how-to-edit-add-units-per-pixel-to-a-tiff-stack/8402>\
**Category:** Support\
**Created:** [September 12, 2019, 12:58pm UTC](https://discourse.slicer.org/t/how-to-edit-add-units-per-pixel-to-a-tiff-stack/8402 "2019-09-12T12:58:13Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![Louis\_Kammerer](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/louis_kammerer/32/4709_2.png) [@Louis\_Kammerer](https://discourse.slicer.org/u/Louis_Kammerer)\
**Post date:** [September 12, 2019, 12:58pm UTC](https://discourse.slicer.org/t/how-to-edit-add-units-per-pixel-to-a-tiff-stack/8402/1 "2019-09-12T12:58:13Z")

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Operating system:windows 10  
Slicer version:4.10.1  
Expected behavior:no units  
Actual behavior:unrealistic units

I am using a file composed of a stack of tiff images from uMRI that I merged using FIJI. When I open this file in slicer it works well. when I use the ruler I get a measurement that is not accurate. I know the size of each pixel, for instance 39x39x39 in microns. Is there a way to add this information?  
Thanks

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [September 12, 2019, 1:50pm UTC](https://discourse.slicer.org/t/how-to-edit-add-units-per-pixel-to-a-tiff-stack/8402/2 "2019-09-12T13:50:48Z")

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I don’t think you can add it to the tiff, but if you save in nrrd or nifti format then the spacing can be preserved.

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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:** [September 12, 2019, 2:00pm UTC](https://discourse.slicer.org/t/how-to-edit-add-units-per-pixel-to-a-tiff-stack/8402/3 "2019-09-12T14:00:55Z")

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> [@Louis\_Kammerer](#):
>
> I know the size of each pixel, for instance 39x39x39 in microns. Is there a way to add this information?

You can edit spacing information manually in Volumes module / Volume Information section. I agree with @pieper that you should choose an image format that can store at least the most basic image geometry information (origin, spacing, axis directions).

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**Author:** ![Louis\_Kammerer](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/louis_kammerer/32/4709_2.png) [@Louis\_Kammerer](https://discourse.slicer.org/u/Louis_Kammerer)\
**Post date:** [September 12, 2019, 2:47pm UTC](https://discourse.slicer.org/t/how-to-edit-add-units-per-pixel-to-a-tiff-stack/8402/4 "2019-09-12T14:47:29Z")

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Thanks that worked! I have been saving as NRRD just loading the original as a tiff. of course any segments I made no longer fit the original and won’t give me accurate measurements, is there any way to scale them?

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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:** [September 12, 2019, 2:58pm UTC](https://discourse.slicer.org/t/how-to-edit-add-units-per-pixel-to-a-tiff-stack/8402/5 "2019-09-12T14:58:47Z")

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You can scale the image and segmentation by applying the same linear transform using Transforms module (scaling factors are the 3 first values in the diagonal of the 4x4 transformation matrix).

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [September 12, 2019, 10:06pm UTC](https://discourse.slicer.org/t/how-to-edit-add-units-per-pixel-to-a-tiff-stack/8402/6 "2019-09-12T22:06:15Z")

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Or you can export them as labelmap volume nodes and edit the spacing in the volumes module like you did for the background. Then you can re-import them as segmentation. (Import export controls are at the bottom of the Segmentations module).

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**Author:** ![Louis\_Kammerer](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/louis_kammerer/32/4709_2.png) [@Louis\_Kammerer](https://discourse.slicer.org/u/Louis_Kammerer)\
**Post date:** [December 4, 2019, 5:33am UTC](https://discourse.slicer.org/t/how-to-edit-add-units-per-pixel-to-a-tiff-stack/8402/7 "2019-12-04T05:33:29Z")

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Do you know a way to make the linear transform reduce by 3 decimal places? right now I can only get two in the boxes.

When I import the exported labelmap nodes I can’t select them as an active volume to change their image spacing.

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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 4, 2019, 7:37am UTC](https://discourse.slicer.org/t/how-to-edit-add-units-per-pixel-to-a-tiff-stack/8402/8 "2019-12-04T07:37:42Z")

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You can press Ctrl++ to increase the number of displayed digits.