Change resolution of a 3D VTK dataset


I am working with a vtk dataset that has both scalar and vector field data, and the vtk type is vtkStructuredPoints. I want to decrease the grid resolution for each field to reduce file size and write the new dataset into a new vtk file using vtkImageResize and SetResizeMethodToOutputSpacing methods from python vtk library:

resize = vtkImageResize()
resize.SetInputData(data) # data is original StructuredPoints dataset
nfactor = 4 # downscaling factor
resize.SetOutputSpacing(dx*nfactor, dy*nfactor, dz*nfactor)

However, it returns me an error ‘vtkImageResize (0x556db860fb30): ThreadedRequestData: output scalar type does not match input scalar type’, and the dataset resolution does not change.
What is the right way to downsample the dataset?
I would appreciate any help!