# \[itk-python\] BlockMatchingImageFilter usage problem
**URL:** https://discourse.itk.org/t/itk-python-blockmatchingimagefilter-usage-problem/3122
**Category:** Engineering
**Tags:** python
**Created:** [May 26, 2020, 6:36pm UTC](https://discourse.itk.org/t/itk-python-blockmatchingimagefilter-usage-problem/3122 "2020-05-26T18:36:03Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@totoro3y](https://discourse.itk.org/u/totoro3y)
#### Post date: [May 26, 2020, 6:36pm UTC](https://discourse.itk.org/t/itk-python-blockmatchingimagefilter-usage-problem/3122/1 "2020-05-26T18:36:03Z")
Hello everyone, I am trying to use BlockMatchingImageFilter to do block matching.
I refered to the c++ example match feature points ([https://itk.org/Doxygen/html/SphinxExamples\_2src\_2Registration\_2Common\_2MatchFeaturePoints\_2Code\_8cxx-example.html#\_a1](https://itk.org/Doxygen/html/SphinxExamples_2src_2Registration_2Common_2MatchFeaturePoints_2Code_8cxx-example.html#_a1)) and wrote the following codes,
```python
Dimension = 2
CoordType = itk.F
PointSetType = itk.PointSet[CoordType, Dimension]
pointSet = PointSetType.New()
points = pointSet.GetPoints()
# Create points
point = itk.Point[CoordType,Dimension]()
point[0] = 40
point[1] = 65
points.InsertElement(0, point)
# read images
PixelType = itk.F
n = 200
path_tr = '../training'
name = '_2CH_ES'
sample = 'patient'+str(n).zfill(4)+'/patient'+str(n).zfill(4)+name+'.mhd'
img_es = itk.imread(os.path.join(path_tr,sample),PixelType)
name = '_2CH_ED'
sample = 'patient'+str(n).zfill(4)+'/patient'+str(n).zfill(4)+name+'.mhd'
img_ed = itk.imread(os.path.join(path_tr,sample),PixelType)
ImageType = itk.Image[PixelType,3]
# block matching
block_filter = itk.BlockMatchingImageFilter[ImageType].New()
block_filter.SetFixedImage(img_ed)
block_filter.SetMovingImage(img_es)
block_filter.SetFeaturePoints(points)
block_filter.UpdateLargestPossibleRegion()
```
# Error
I got an error : in method ‘itkBlockMatchingImageFilterIF3\_SetFeaturePoints’, argument 2 of type ‘itkPointSetMD33STMD3333FFMD33 const \*’. Does anyone know how to make the pointset type to be MD33STMD3333FFMD33??
Thank you for your help!!!
---
### Author:  [@dzenanz](https://discourse.itk.org/u/dzenanz)
#### Post date: [May 26, 2020, 6:44pm UTC](https://discourse.itk.org/t/itk-python-blockmatchingimagefilter-usage-problem/3122/2 "2020-05-26T18:44:17Z")
> [@totoro3y](#):
>
> CoordType = itk.F
Did you try `itk.D`? `double`s are more commonly used for everything else except pixel type.
---
### Author:  [@totoro3y](https://discourse.itk.org/u/totoro3y)
#### Post date: [May 26, 2020, 7:38pm UTC](https://discourse.itk.org/t/itk-python-blockmatchingimagefilter-usage-problem/3122/3 "2020-05-26T19:38:03Z")
Hello! Thank you for your reply!
Yes, I have tried the itk.D and i still got the same error.
I used help() function to check the type of arguments in Blockmatchingfilter and i got:
> Help on itkBlockMatchingImageFilterIF3 in module itkBlockMatchingImageFilterPython object:
> class itkBlockMatchingImageFilterIF3(itkBlockMatchingImageFilterIF3\_Superclass)
> | Computes displacements of given points from a fixed image in a
> | floating image.
> | …
> | …
> | …
> | SetFeaturePoints = itkBlockMatchingImageFilterIF3\_SetFeaturePoints(…)
> | itkBlockMatchingImageFilterIF3\_SetFeaturePoints( **itkBlockMatchingImageFilterIF3** self, **itkPointSetMD33STMD3333FFMD33** \_arg)
> |
> | SetFixedImage = itkBlockMatchingImageFilterIF3\_SetFixedImage(…)
> | itkBlockMatchingImageFilterIF3\_SetFixedImage(itkBlockMatchingImageFilterIF3 self, itkImageF3 \_arg)
> |
> | SetMovingImage = itkBlockMatchingImageFilterIF3\_SetMovingImage(…)
> | itkBlockMatchingImageFilterIF3\_SetMovingImage(itkBlockMatchingImageFilterIF3 self, itkImageF3 \_arg)
> | …
I know that **itkBlockMatchingImageFilterIF3** should be an image object of float type and with dimension 3, but i am totally lost by the definition of **itkPointSetMD33STMD3333FFMD33**.
Do you have any idea what does it mean? How could i define the pointset object?
( In the c++ example, the pointset object was defined as following
> using PointSetType = BlockMatchingImageFilterType::FeaturePointsType;
> using PointType = PointSetType::PointType;
> using PointsContainerPointer = PointSetType::PointsContainerPointer;
> PointSetType::Pointer pointSet = PointSetType::New();
> PointsContainerPointer points = pointSet-\>GetPoints();
Thank you very much!
---
### Author:  [@totoro3y](https://discourse.itk.org/u/totoro3y)
#### Post date: [May 26, 2020, 7:47pm UTC](https://discourse.itk.org/t/itk-python-blockmatchingimagefilter-usage-problem/3122/4 "2020-05-26T19:47:46Z")
I got the type of pointset needed in this filter
> itk::PointSet\, 3u, itk::DefaultStaticMeshTraits\3u, 3u, float, float, itk::Matrix\ \> \>
This is quite complicated…
---
### Author:  [@dzenanz](https://discourse.itk.org/u/dzenanz)
#### Post date: [May 26, 2020, 7:50pm UTC](https://discourse.itk.org/t/itk-python-blockmatchingimagefilter-usage-problem/3122/5 "2020-05-26T19:50:01Z")
I remember there was a [problem with wrapping mesh traits](https://github.com/InsightSoftwareConsortium/ITKExamples/pull/66/commits/71a37b790cf0832c2b9ce7f229e5ea016e866ab0#diff-a6d670e5b306f15e0176a9b64c158cf2R29), but I don’t know whether that has been fixed meanwhile. @matt.mccormick is `BlockMatchingImageFilter`'s wrapping supposed to work?
---
### Author:  [@matt.mccormick](https://discourse.itk.org/u/matt.mccormick)
#### Post date: [June 8, 2020, 10:59pm UTC](https://discourse.itk.org/t/itk-python-blockmatchingimagefilter-usage-problem/3122/6 "2020-06-08T22:59:09Z")
> [@totoro3y](#):
>
> I got the type of pointset needed in this filter
>
> > itk::PointSet\, 3u, itk::DefaultStaticMeshTraits\3u, 3u, float, float, itk::Matrix\ \> \>
>
> This is quite complicated…
These classes squeaked past the mesh simplification of ITK 5.0 – I’ll see if we can improve on that.
> [@totoro3y](#):
>
> How could i define the pointset object?
These feature points are meant to be generated by the `itk.MaskFeaturePointSelectionFilter` as described in the [corresponding article](https://www.frontiersin.org/articles/10.3389/fninf.2014.00033/full).
---
### Author:  [@matt.mccormick](https://discourse.itk.org/u/matt.mccormick)
#### Post date: [June 10, 2020, 2:32pm UTC](https://discourse.itk.org/t/itk-python-blockmatchingimagefilter-usage-problem/3122/7 "2020-06-10T14:32:23Z")
> [@matt.mccormick](#):
>
> These classes squeaked past the mesh simplification of ITK 5.0 – I’ll see if we can improve on that.
This was addressed here:
>
>
> …ngling
>
> Simplify the Python wrapping name mangling to remove the
> DefaultStat…icMeshTraits, standard with itk 5 mesh wrapping.