cal_max and cal_min slots to
be the max and min, respectively, of an object of class nifti, with
na.rm = TRUE. This is so that when images are rendered/written,
the values correspond to those in the array (stored in .Data slot)
are plotted on correct greyscale and no error is given by writeNIfTI.
calibrateImage(img, infok = TRUE)
cal_img(img, infok = TRUE)nifti object.Inf and
-Inf are acceptable (default = TRUE). If FALSE
and max or min is infinity, then cal_min or cal_max is
set to infinity (negative or positive), respectively.nifti.