# Vector type single channel image
**URL:** https://discourse.itk.org/t/vector-type-single-channel-image/7575
**Category:** Beginner Questions
**Tags:** vector, simpleitk
**Created:** [June 25, 2025, 12:20pm UTC](https://discourse.itk.org/t/vector-type-single-channel-image/7575 "2025-06-25T12:20:12Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Franciska](https://discourse.itk.org/u/Franciska)
#### Post date: [June 25, 2025, 12:20pm UTC](https://discourse.itk.org/t/vector-type-single-channel-image/7575/1 "2025-06-25T12:20:12Z")
I have a dicom image thats shape is (1136, 852, 1) and PixelID is ‘vector of 8-bit unsigned integer’ . I want to cast this to float32 but as I can not cast vector type to simple float, following online advice I tried:
> sitk\_scan = sitk.Cast(sitk\_scan, sitk.sitkVectorFloat32)
> sitk\_scan = sitk\_scan[:,:,0]
But afterwards its shape is (1136, 852) and PixelID is vector of 32-bit float. And I still can not cast this to sitkFloat32.
> sitk::ERROR: Filter does not support casting from casting vector of 32-bit float to 32-bit float
So how can I cast this 1 channel image into a simple sitkFloat32 type?
---
### Author:  [@zivy](https://discourse.itk.org/u/zivy)
#### Post date: [June 25, 2025, 1:07pm UTC](https://discourse.itk.org/t/vector-type-single-channel-image/7575/2 "2025-06-25T13:07:31Z")
Hello @Franciska,
The meaning of the original pixel type ‘vector of 8-bit unsigned integer’ is that for every pixel you have multiple values (likely a three channel image). This can mean that the image is a color image in RGB color space or that it is a scalar/grayscale image masquerading as a color one, a single channel repeated three times.
Given your desire to convert this image type to float32 and not a vector of float32 you are likely assuming this is a scalar image. To extract the first channel and cast to float, then convert to a 2D image from a 3D slice:
```auto
sitk_scan = sitk.VectorIndexSelectionCast(sitk_scan, 0, sitk.sitkFloat32)
sitk_scan = sitk_scan[:,:,0]
```
To characterize data before working with it, take a look at the [characterize\_data.py script](https://github.com/InsightSoftwareConsortium/SimpleITK-Notebooks/blob/master/Python/scripts/characterize_data.py) in the [SimpleITK notebooks repository](https://github.com/InsightSoftwareConsortium/SimpleITK-Notebooks). The data may surprise you, content is not what it visually looks like, vector images that visually look like a scalar, color images that should be scalar/grayscale etc.
---
### Author:  [@blowekamp](https://discourse.itk.org/u/blowekamp)
#### Post date: [June 25, 2025, 1:09pm UTC](https://discourse.itk.org/t/vector-type-single-channel-image/7575/3 "2025-06-25T13:09:54Z")
Hello,
The concepts in SimpleITK/ITK are a little different than in numpy. In SimpleITK/ITK an Image has a size (x,y,z…) and the number of components ( defaults to 1 for scalars). So in `(1136, 852,1)`, the 1 is the size in the z dimension not the number of components. Based on the information provided, we don’t know how many channels are in the sitk\_scan image.
You should display all the details of your original sitk\_scan image with `print(sitk_scale.ToString())`. If the image of a vector pixel type, it will say “VectorImage”, and later say “VectorLength: 3” or similar. This can be accessed via the sitk::Image interface with [`GetNumberOfComponentsPerPixel`](https://simpleitk.org/doxygen/latest/html/classitk_1_1simple_1_1Image.html#abb8b4188222fc781607ab26c69fc5423).
The 3D image of vectors can becopied to a 4D image of scalar with `sitk_scan4d = sitk_scan.ToVector(inPlace=false)` which may be want you are expecting.
The [`VectorIndexSelectionCastImageFilter`](https://simpleitk.org/doxygen/latest/html/classitk_1_1simple_1_1VectorIndexSelectionCastImageFilter.html) can be used to select a specific channel. And the [`VectorMagnitudeImageFilter`](https://simpleitk.org/doxygen/latest/html/classitk_1_1simple_1_1VectorMagnitudeImageFilter.html) can be use to compute the l2 norm to get a scalar.