# File sizes after making a volume isotropic

**URL:** <https://discourse.slicer.org/t/file-sizes-after-making-a-volume-isotropic/37540>\
**Category:** Support\
**Created:** [July 24, 2024, 9:48am UTC](https://discourse.slicer.org/t/file-sizes-after-making-a-volume-isotropic/37540 "2024-07-24T09:48:26Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![coco](https://avatars.discourse-cdn.com/v4/letter/c/8797f3/32.png) [@coco](https://discourse.slicer.org/u/coco)\
**Post date:** [July 24, 2024, 9:48am UTC](https://discourse.slicer.org/t/file-sizes-after-making-a-volume-isotropic/37540/1 "2024-07-24T09:48:26Z")

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Dear all,  
I was astonished to see a dramatic drop in file size after using the crop volume module and I don’t understand why.  
Here is my original volume volume information:  
 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/d/f/df7a009c8adb8bc913f87ba68441d3a3db7f19f8.png)  
Now this is my new volume information after crop volume (using a roi to the full frame, B spline and isotropic spacing):  
 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/3/9/39e9e616d6867b3ac46befadbcaac601185315cb.png)  
Note that I changed the units in the \_iso file manually to the right scale (um instead of mm) before running the crop volume

Now if I save the isotropic file, the space used on disk is 2.3 G compared to 6.3 G for the original file.

How come ?

Many thanks to the community and developpers for help and of course, a great software !

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**Author:** ![muratmaga](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/muratmaga/32/3622_2.png) [@muratmaga](https://discourse.slicer.org/u/muratmaga)\
**Post date:** [July 24, 2024, 4:18pm UTC](https://discourse.slicer.org/t/file-sizes-after-making-a-volume-isotropic/37540/2 "2024-07-24T16:18:54Z")

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Your second volume (the one generated after cropping) is actually larger than the original one (there are more voxels in Z dimension).

If you choose to compress the file during the save, the file size will be smaller than the memory footprint required to load the file. I presume your original file was not compressed. So that’s probably where the difference is coming from.

For large files like this, I suggest not compressing them. Most of the wait during the save/open operations are actually spend on compressing/uncompressing them as the compression library used is single-threaded.

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**Author:** ![coco](https://avatars.discourse-cdn.com/v4/letter/c/8797f3/32.png) [@coco](https://discourse.slicer.org/u/coco)\
**Post date:** [July 25, 2024, 7:44am UTC](https://discourse.slicer.org/t/file-sizes-after-making-a-volume-isotropic/37540/3 "2024-07-25T07:44:14Z")

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Thanks Murat,  
indeed I expected files larger, not smaller as there are more voxels in the Z dimensions.  
In the save tab, I clicked on show options and noticed “compress” was checked. I had forgotten about that option but I probably did this voluntary at some point: I think in my case, storage space is more of a concern than time openning/saving (it s still very fast on my cluster, for files up to 15 GB, I hardly wait).  
Perhaps that option should not be “hidden” as I simply forgot about that and went along my pipeline.  
S

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**Author:** ![muratmaga](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/muratmaga/32/3622_2.png) [@muratmaga](https://discourse.slicer.org/u/muratmaga)\
**Post date:** [July 25, 2024, 12:41pm UTC](https://discourse.slicer.org/t/file-sizes-after-making-a-volume-isotropic/37540/4 "2024-07-25T12:41:56Z")

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If you are using SlicerMorph, go to Application Settings-\>SlicerMorph then check use SlicerMorph customizations and restart Slicer. This will disable compression option for all your volume data.