pro meanvar,name,num,imean,ivar,hb,clean=clean,norm=norm,dark=dkim
; 
; This procedure computes the mean and variance of a set of 2-byte 
; integer images acquired by a CCD camera. It accepts as inputs the 
; base file name of the images. It returns two floating-point images, 
; containing the mean and the variance of the input images, 
; respectively. 
;
; If the clean keyword is set, an attempt is made to remove CCD hot
; pixels before adding each image to the sums.
; If the norm keyword is set, each image is converted to 2-byte
; INTEGER form and normalized so that its brightest pixel has a
; value of 10000.
;
; If the dark keyword is set, it is an input dark image to be
; subtracted from each image read from disk (before normalizing,
; if this option is selected).
; 
; Modified 20 Oct 1993 by D. P. Steele to find the files that match 
; the base name (including path) supplied by the user. 
; 
f=FINDFILE(name,COUNT=num) 
IF num LE 0 THEN BEGIN 
    MESSAGE,'No files found matching supplied name.' 
    RETURN 
    ENDIF 
FOR j=0,num-1 DO BEGIN 
;   get j-th image 
    rdkimg,f(j),hb,ij 
    IF j EQ 0 THEN BEGIN ;set things up the first time around
        s=SIZE(ij) 
        w=s(1)
        h=s(2)
        isum=LONARR(w,h) 
        isumsq=DBLARR(w,h) 
        ENDIF 
;   remove hot pixels 
    IF KEYWORD_SET(clean) THEN img=clean(ij,2,2,3) ELSE img=ij 
    IF KEYWORD_SET(dkim) THEN img=(img-dkim)>0
    IF KEYWORD_SET(norm) THEN BEGIN
        ; Find the 'center of gravity' of the image, and look for the
        ; maximum pixel value in that neighbourhood
        IF j EQ 0 THEN BEGIN
            cols=REPLICATE(FINDGEN(w),1,h)
            rows=TRANSPOSE(cols)
            STOP,'Check out cols and rows arrays!'
            ENDIF
        cgcol=TOTAL(cols*img)/(w*h)
        cgrow=TOTAL(rows*img)/(w*h)
        IF j lt 5 THEN STOP,'cgcol=',cgcol,'cgrow=',cgrow
        mk,mask
        mask(cgcol-32:cgcol+32,cgrow-32:cgrow+32)=1
        maxpix=MAX(img*mask,loc)
        one2two,loc,img,maxcol,maxrow
        PRINT,j,maxpix,maxcol,maxrow,FORMAT='("Image ",'+ $
        'I3,": max pixel value=",I6," at col ",I3,", row ",I3)'
        img=FIX(ROUND((10000.*img)/maxpix))
        ENDIF
;   update sum and sum of squares of images 
    isum=isum+img 
    isumsq=isumsq+LONG(img)^2 
    ENDFOR 
n=DOUBLE(num) 
imean=FIX(ROUND(isum/n)) 
ivar=((isumsq-n*(isum/n)^2)/(n-1)) 
IF MIN(ivar) LT 0 THEN MESSAGE,'The variance image has negative elements!' 
RETURN 
END