# MultiScaleHessianBasedMeasureImageFilter GetScalesOutput() member function doesn't work in python?
**URL:** https://discourse.itk.org/t/multiscalehessianbasedmeasureimagefilter-getscalesoutput-member-function-doesnt-work-in-python/6518
**Category:** Algorithms
**Created:** [March 15, 2024, 2:11pm UTC](https://discourse.itk.org/t/multiscalehessianbasedmeasureimagefilter-getscalesoutput-member-function-doesnt-work-in-python/6518 "2024-03-15T14:11:49Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Chuck\_Hatt](https://discourse.itk.org/u/Chuck_Hatt)
#### Post date: [March 15, 2024, 2:11pm UTC](https://discourse.itk.org/t/multiscalehessianbasedmeasureimagefilter-getscalesoutput-member-function-doesnt-work-in-python/6518/1 "2024-03-15T14:11:50Z")
Getting an error when I try write to file or get the numpy array associated with the GetScalesOutput() function for MultiScaleHessianBasedMeasureImageFilter in python.
```auto
# Load itk_image from file
ImageType = type(itk_image)
HessianPixelType = itk.SymmetricSecondRankTensor[itk.D, DIM]
HessianImageType = itk.Image[HessianPixelType, DIM]
objectness_filter = itk.HessianToObjectnessMeasureImageFilter[
HessianImageType, ImageType
].New()
objectness_filter.SetBrightObject(True)
objectness_filter.SetScaleObjectnessMeasure(True)
objectness_filter.SetAlpha(0.5)
objectness_filter.SetBeta(1.0)
objectness_filter.SetGamma(5.0)
multi_scale_filter = itk.MultiScaleHessianBasedMeasureImageFilter[
ImageType, HessianImageType, ImageType
].New()
multi_scale_filter.SetInput(itk_image)
multi_scale_filter.SetHessianToMeasureFilter(objectness_filter)
multi_scale_filter.SetSigmaStepMethodToLogarithmic()
multi_scale_filter.SetSigmaMinimum(0.5)
multi_scale_filter.SetSigmaMaximum(5.5)
multi_scale_filter.SetNumberOfSigmaSteps(5)
multi_scale_filter.Update()
output_image = multi_scale_filter.GetOutput()
scales_image = multi_scale_filter.GetScalesOutput()
itk.imwrite(scales_image, "scales.nii.gz")
```
Results in:
```auto
...
itk.imwrite(scales_image, "scales.nii.gz")
File "/usr/local/lib/python3.9/site-packages/itk/support/extras.py", line 1176, in imwrite
writer.Update()
RuntimeError: /work/ITK-source/ITK/Modules/IO/ImageBase/include/itkImageFileWriter.hxx:366:
Did not get requested region!
Requested:
ImageRegion (0x7ffc5ce5b380)
Dimension: 3
Index: [0, 0, 0]
Size: [188, 217, 259]
Actual:
ImageRegion (0x7ffc5ce5b340)
Dimension: 3
Index: [0, 0, 0]
Size: [0, 0, 0]
```
Running the same code but trying to access the numpy array does the following
```auto
itk.GetArrayFromImage(scales_image, keep_axes=True)
```
gives this error:
```auto
*** ValueError: PyMemoryView_FromBuffer(): info->buf must not be NULL
```
None of these errors occur when using the GetOutput() method.
This is ITK 5.3.0 and python 3.9
---
### Author:  [@dzenanz](https://discourse.itk.org/u/dzenanz)
#### Post date: [March 15, 2024, 2:59pm UTC](https://discourse.itk.org/t/multiscalehessianbasedmeasureimagefilter-getscalesoutput-member-function-doesnt-work-in-python/6518/2 "2024-03-15T14:59:30Z")
You seem to be missing `multi_scale_filter.SetGenerateScalesOutput( True )`.
---
### Author:  [@Chuck\_Hatt](https://discourse.itk.org/u/Chuck_Hatt)
#### Post date: [March 15, 2024, 3:17pm UTC](https://discourse.itk.org/t/multiscalehessianbasedmeasureimagefilter-getscalesoutput-member-function-doesnt-work-in-python/6518/3 "2024-03-15T15:17:32Z")
> [@dzenanz](#):
>
> multi\_scale\_filter.SetGenerateScalesOutput( True )
Thank you, that was my problem. Adding that fixed the issue.