function center2,i,x,y,l
;+
; NAME:
;	center2
; PURPOSE:
;	Centroiding routine.
;	By integrating over the pixel values of a set area, this function returns
;	the coordinates of the center of the object.  This function is called by
;	the procedures I_DIS and I_CENTER in the procedure I_BROWSE.
; CATEGORY:
;	Image analysis.
; CALLING SEQUENCE:
;	c=center2(i,x,y)
;			;returns the center coordinates, c, from a 26 pixel square
;			;with x,y as the center of the square and i as the image 
;			;being used
;	c=center2(i,x,y,l)
;			;same as above except it uses a square of size l pixels
;			;rather than 26 pixels
; INPUTS:
;	i: the image array being used
;	x: the x coordinate of the center of the square to centroid on
;	y: the y coordinate of the center of the square to centroid on
; OPTIONAL INPUT PARAMETERS:
;	l: the size of the square to centroid on
; KEYWORDS:
; OUTPUTS:
;	Prints the resulting center coordinates, and returns them as the vector c
; OPTIONAL OUTPUT PARAMETERS:
;	NONE
; COMMON BLOCKS:
;	NONE:
; SIDE EFFECTS:
;	NONE
; RESTRICTIONS:
;	NONE
; PROCEDURE:
;	enter i,x,and y and it returns the centroiding results
; MODIFICATION HISTORY:
;	NLC - 03/25/95	created
;-
 


; CHECKS TO SEE IF l WAS ENTERED OR NOT

if n_params(0) EQ 3 then l=26


; DEFINE THE SQUARE TO USE ORIGINALLY
xs=round(x-l/2)
ys=round(y-l/2)

; THE CENTROID IS DETERMINED ITERATIVELY BY EACH TIME MAKING THE SQUARE SLIGHTLY
;SMALLER - IT DOES THIS FOUR TIMES
for z=1,4 do begin


;MAKING A SUBIMAGE OF THE SQUARE AREA TO CENTROID ON
for j=ys,ys+l do begin
for k=xs,xs+l do begin
if k EQ xs then si=i(k,j) else si=[si,i(k,j)]
endfor
if j EQ ys then sit=si else sit=[[sit],[si]]
endfor

; SETTING VALUES THAT ARE BELOW THE NOISE LEVEL TO ZERO
maxi=max(sit)
cut=sqrt(maxi/30)

for p=0,l do begin
for q=0,l do begin
if sit(q,p) LT cut then sit(q,p)=0
endfor
endfor

; CREATING TWO ARRAYS THAT CONTAIN THE PIXEL VALUES WEIGHTED CORRECTLY BY THEIR
; X AND Y DISTANCES FROM THE TOP LEFT CORNER
b=0
for n=0,l do begin
a=0
for m=0,l do begin
if m EQ 0 then mx=a*sit(m,n) else mx=[mx,a*sit(m,n)]
if m EQ 0 then my=b*sit(m,n) else my=[my,b*sit(m,n)]
a=a+1
endfor

if n EQ 0 then mxt=mx else mxt=[[mxt],[mx]]
if n EQ 0 then myt=my else myt=[[myt],[my]]
b=b+1
endfor

; TOTALING THE UNWEIGHTED PIXEL VALUES, AND THE WIEGTHED X AND Y ARRAYS
t=total(sit)
tx=total(mxt)
ty=total(myt)

; COMPUTING THE COORDINATES OF THE CENTER
xc=tx/t+xs
yc=ty/t+ys

; LOOPING IF NECESSARY
if z EQ 1 then l=l-4
if z EQ 2 then l=l-2
if z EQ 3 then l=l-2

; USING A NEW SQUARE SIZE IF STILL LOOPING
xs=round(xc-l/2)
ys=round(yc-l/2)


endfor


; DISPLAYING AND RETURNING THE RESULT
print,'Center:',[xc,yc]
return, [xc,yc]

end