docstr: Initialize resel image
  
  Parameters
  ----------
  resels : `core.api.Image`
      Image of resel per voxel values.
  fwhm : `core.api.Image`
      Image of FWHM values.
  keywords : ``dict``
      Passed as keywords arguments to `core.api.Image`
docstr_tok: ["Initialize","resel","image","Parameters","--","--","--","--","--","resels",":","`","core.api.Image","`","Image","of","resel","per","voxel","values",".","fwhm",":","`","core.api.Image","`","Image","of","FWHM","values",".","keywords",":","``","dict","``","Passed","as","keywords","arguments","to","`","core.api.Image","`"]
code: def __init__(self, resels=None, fwhm=None, **keywords):
      """Initialize resel image
  
      Parameters
      ----------
      resels : `core.api.Image`
          Image of resel per voxel values.
      fwhm : `core.api.Image`
          Image of FWHM values.
      keywords : ``dict``
          Passed as keywords arguments to `core.api.Image`
      """
      if not resels and not fwhm:
          raise ValueError(
              "need either a resels image or an FWHM image"
          )
  
      if fwhm is not None:
          fwhm = Image(fwhm, **keywords)
          Resels.__init__(self, fwhm, resels=resels, fwhm=fwhm)
  
      if resels is not None:
          resels = Image(resels, **keywords)
          Resels.__init__(self, resels, resels=resels, fwhm=fwhm)
  
      if not self.fwhm:
          self.fwhm = Image(
              self.resel2fwhm(self.resels[:]),
              coordmap=self.coordmap,
              **keywords,
          )
  
      if not self.resels:
          self.resels = Image(
              self.fwhm2resel(self.fwhm[:]),
              coordmap=self.coordmap,
              **keywords,
          )
  
file_path: nipy/nipy/algorithms/fwhm.py
imports: import numpy
  from numpy.linalg import det
  from nipy.core.api import Image
  from .utils.matrices import pos_recipr
label_desc: Use image node_id 1 to create a new ReselImage object from inherited base classes: Resels with example: obj = ReselImage(resels, fwhm)