PRO maxdn,year,month,day
;
; This procedure scans any 'ilists' for the specified date, and
; for each 'ilist', outputs a list of the useful maximum DN necessary
; to represent each listed image.  The output lists can be used to
; set full-scale DN's for image plots in advance.
;
; Algorithm:
;   for each ilist:
;     read ilist
;     scan list and identify needed dark frames
;     read in needed dark frames a la ql.pro
;     for each 1- or 10-second image in list
;       read in each image in list
;       subtract appropriate dark frame
;       determine useful upper limit DN a la ql.pro
;       write DN entry to vector of max DN's
;     open output file
;     write out max DN and file name (similar format to 'ilist' files)
;
mask=BYTARR(256,256)
s=''
; define mask for images, with fixed horizon at 150 superpixels 
prad=150
d256=SHIFT(dist(256),128,128) & base=WHERE(d256 GT 150)
wprad=WHERE(d256 LE prad) & mask(wprad)=1

; make lists of available files of desired type
hr=0B & min=hr & sec=hr
rdilist,0,year,month,day,hr,min,sec,n0,t0,files0
maxDN0=INTARR(n0)
rdilist,1,year,month,day,hr,min,sec,n1,t1,files1
maxDN1=INTARR(n1)

; read in or generate required dark frames
dkt=0
dkim=INTARR(1,512)
dkpair=INTARR(256,512)
FOR i=0,n0-1 DO BEGIN
    exp0=FIX(STRMID(files0(i),STRLEN(files0(i))-7,3))
    we=WHERE(exp0 EQ dkt,nwe)
    IF nwe EQ 0 THEN BEGIN	; haven't got this exposure time yet
        rdmeandk,0,exp0,dk0
        rdmeandk,1,exp0,dk1
        dkpair(*,0:255)=dk0
        dkpair(*,256:511)=dk1
        dkt=[dkt,exp0]
        dkim=[dkim,dkpair]
    ENDIF
ENDFOR
FOR i=0,n1-1 DO BEGIN		; repeat above process for camera 1
    exp1=FIX(STRMID(files1(i),STRLEN(files1(i))-7,3))
    we=WHERE(exp1 EQ dkt,nwe)
    IF nwe EQ 0 THEN BEGIN	; haven't got this exposure time yet
        rdmeandk,0,exp1,dk0
        rdmeandk,1,exp1,dk1
        dkpair(*,0:255)=dk0
        dkpair(*,256:511)=dk1
        dkt=[dkt,exp1]
        dkim=[dkim,dkpair]
    ENDIF
ENDFOR
dkt=dkt(1:*)		; drop dummy entry at start of array
dkim=dkim(1:*,*)	; drop dummy column ...

; read in each image, rebin to 256x256 if necessary, subtract dark
; frame, compute histogram of exposed part of image, and find DN
; > 99.9% of exposed pixels
;
; camera 0 images first
;
FOR i=0,n0-1 DO BEGIN
    s=files0(i)
    exp=FIX(STRMID(s,STRLEN(s)-7,3))
    IF exp LE 10 THEN BEGIN
        rdkimg,s,h,im
        IF N_ELEMENTS(im) NE 65536L THEN BEGIN
	    im=REBIN(im,256,256)
; ensure counts are actually summed if a 512x512 image is compressed
            cfac=512/(256*KIh.exp.sbin)
            rfac=512/(256*KIh.exp.pbin)
            im=im*cfac*rfac
        ENDIF
; subtract appropriate dark frame
        dp=WHERE(dkt EQ exp)
        im=(im-dkim(256*dp(0):256*dp(0)+255,0:255))>0
; identify useful min and max values for byte-scaling
        ih=HISTOGRAM(im(wprad),MIN=0,BIN=1)	; histogram of exposed image
        cih=ih	; next line computes cumulative pixel value pdf
        FOR jj=1,N_ELEMENTS(cih)-1 DO cih(jj)=cih(jj)+cih(jj-1)
        cih=cih/FLOAT(MAX(cih))		; normalize to unity
	maxDN0(i)=MAX(WHERE(cih LE .999))   ; top 0.1% of pixels saturate
	IF (i+1) MOD 50 EQ 0 THEN PRINT,STRTRIM(i+1,2)+' images processed'
    ENDIF
ENDFOR
ww=WHERE(maxDN0)
files0=files0(ww)
maxDN0=maxDN0(ww)
outname='/jasper/cnsr3_data1/ilist/'+ $
	STRING(year,month,day,FORMAT='(3I2.2,".0.maxDN")')
OPENW,u0,outname,/GET_LUN
FOR i=0,N_ELEMENTS(ww)-1 DO $
    PRINTF,u0,maxDN0(i),files0(i),FORMAT='(I5,3X,A45)'
CLOSE,u0
FREE_LUN,u0

; then camera 1
;
FOR i=0,n1-1 DO BEGIN
    s=files1(i)
    exp=FIX(STRMID(s,STRLEN(s)-7,3))
    IF exp LE 10 THEN BEGIN
        rdkimg,s,h,im
        IF N_ELEMENTS(im) NE 65536L THEN BEGIN
	    im=REBIN(im,256,256)
; ensure counts are actually summed if a 512x512 image is compressed
            cfac=512/(256*KIh.exp.sbin)
            rfac=512/(256*KIh.exp.pbin)
            im=im*cfac*rfac
        ENDIF
; subtract appropriate dark frame
        dp=WHERE(dkt EQ exp)
        im=(im-dkim(256*dp(0):256*dp(0)+255,256:511))>0
; identify useful min and max values for byte-scaling
        ih=HISTOGRAM(im(wprad),MIN=0,BIN=1)	; histogram of exposed image
        cih=ih	; next line computes cumulative pixel value pdf
        FOR jj=1,N_ELEMENTS(cih)-1 DO cih(jj)=cih(jj)+cih(jj-1)
        cih=cih/FLOAT(MAX(cih))		; normalize to unity
	maxDN1(i)=MAX(WHERE(cih LE .999))   ; top 0.1% of pixels saturate
	IF (i+1) MOD 50 EQ 0 THEN PRINT,STRTRIM(i+1,2)+' images processed'
    ENDIF
ENDFOR
ww=WHERE(maxDN1)
files1=files1(ww)
maxDN1=maxDN1(ww)
outname='/jasper/cnsr3_data1/ilist/'+ $
	STRING(year,month,day,FORMAT='(3I2.2,".1.maxDN")')
OPENW,u1,outname,/GET_LUN
FOR i=0,N_ELEMENTS(ww)-1 DO $
    PRINTF,u1,maxDN1(i),files1(i),FORMAT='(I5,3X,A45)'
CLOSE,u1
FREE_LUN,u1

END