Gray Image Median filter in IDL

;################################################
;              Median Filter
;         Author : S.Ganesh Babu
;################################################
PRO EX5
file=DIALOG_PICKFILE(PATH='E:\Image')
im=READ_IMAGE(file)
im1=im
sz=SIZE(im,/DIMENSIONS)
s=[0,0,0,0,0,0,0,0,0]
FOR i=1,sz[0]-2 DO BEGIN
FOR j=1,sz[1]-2 DO BEGIN
CO=0;
FOR k = i-1,i+1 DO BEGIN
FOR l = j-1,j+1 DO BEGIN

s[CO]=im[k,l]
CO=CO+1
ENDFOR
ENDFOR
im1[i,j]=MEDIAN(s)
ENDFOR
ENDFOR
WINDOW,0,XSIZE=sz[0],YSIZE=sz[0],TITLE='ORIGINAL IMAGE'
TV,im
WINDOW,1,XSIZE=sz[0],YSIZE=sz[0],TITLE='MEDIAN IMAGE'
TV,im1
END