image 
plot function for object of class nifti
breaker(x, zlim, col, breaks = NULL)niftizlim.  If NULL, will calculate how 
ortho2 would calculate zlimlength(col), so can be a
vector of length cols to be plotted!is.null(breaks), then will calculate breaks.  Otherwise will
return this breaks vectorbreaks = NULL, then vector of length(col) + 1, 
otherwise returns breaks