; NAME:    do_sum_diff.ips
; PURPOSE: Add or difference two images and make the header
; RESTRICTION:
;	SCALESUM can only have the source/dest pages from 0-7 and 16-19.
; HISTORY: Written 29-Feb-96 by M.Morrison
;
;
QSR_DO_SUM::
    SETREG $IPRL_SUMDIFF_WORK+9 1
    GOTO &COMMON_CODE

QSR_DO_DIFF::
    SETREG $IPRL_SUMDIFF_WORK+9 0xFFFF

COMMON_CODE:
;-------- Setup and do the calculation
    COPYRD2D $IPRL_SUMDIFF_PARAM   $IPRL_SUMDIFF_WORK 6		;copy two source pages and destination
    COPYREG  $IPRL_SUMDIFF_PARAM+6 $IPRL_SUMDIFF_WORK+10	;copy the shift factor

    _SCALESUM    $IPRL_SUMDIFF_WORK			

;-------- decode the source and destination page info
    COPYREG  $IPRL_SUMDIFF_PARAM+1 $IPRL_HDECODE_PARAM		;copy the source page high word into a known fixed place
    COPYREG  $IPRL_SUMDIFF_PARAM+5 $IPRL_HDECODE_PARAM+1	;copy the dest page high word into a known fixed place
    CALLQUE  $QSR_DO_HDECODE					;decode the value - 

;-------- now copy the relevant info to the hrdinit slot and make the header
    COPYRI2D $IPRP_HDECODE_ADDR+1     $IPRL_HEAD_WORK 10	;copy the register list to a fixed working area
    COPYRD2D $IPRL_SUMDIFF_PARAM+4    $IPRL_HEAD_WORK+6 4	;copy the final dest(l,h), # of pix (l,h)
    COPYRD2D $IPRL_SUMDIFF_PARAM+7    $IPRL_HEAD_WORK+3 3	;copy n/k, dpc(l), and dpc(h) into the HRDINIT slot
    COPYRD2I $IPRL_HEAD_WORK          $IPRP_HDECODE_ADDR+1 10	;copy the register list back to the slot

    CALLQUE  $QSR_DO_HEADER
    RTNQUE