"w" for warped.  There are many ways to warp an image, and what you do should depend on how you intend to use the processed data.  Ther are a few differnt algorithms in SPM for doing this, and each gives a different output.

Best regards,

On 23 June 2015 at 16:06, 付振荣 <[log in to unmask]> wrote:
dear author:
      I‘m very glad to hear form you !
      my last letter,ask how to use spm for VBM .
     I also want to ask another question about the    batch-----spm-----Util----deformations
    after we get the c1,c2,rc1,rc2,y,iy     
  to inverse  the image 
  compositon--deformation field---y.nii
            apply to  --- xxxxx.img(rawdata)
  the result of it is a file begin with w

 compare the image   xxxxx.img(rawdata) with the filename begin with the w  ,
  they are different.
 but i think they are in the same space and the scale will be same .why?
best wishs