!------------------------------------------------------------------------
! @LEVEL.NIC
! Procedure to define contour levels for multichannel image
! Variables defined in DEFINE.NIC
!------------------------------------------------------------------------
define real range expo mant 
define integer n1 n2
!
if spacing.lt.0 then
    return
endif
if (&1%extrema.eq.0) then		! means no extrema section
    del /var &1
    define image &1 'name'.'type' write /global
    compute &1%min min &1
    compute &1%max max &1
    let &1%extrema 40
    del /var aaa
    define image &1 'name'.'type' read /global
endif
if (levels.eq."ABS") then
 if (spacing.eq.0) then
    let range log10(&1%max-&1%min)
    let expo int(range+20.)-21
    let mant range-expo-1
    if (mant.lt.0.25) then
	let true_spacing 10**expo
    else if (mant.lt.0.60) then
	let true_spacing 2.*10**expo
    else if (mant.lt.0.90) then
	let true_spacing 5.*10**expo
    else
	let true_spacing 10**(expo+1)
    endif
  else
    let true_spacing spacing
 endif
 let n1 max(-20,nint(&1%min|true_spacing))
 let n2 min(+20,nint(&1%max|true_spacing))
 levels true_spacing*n1 to -0.95*true_spacing by true_spacing -
 true_spacing to true_spacing*(n2+0.05) by true_spacing
else
 if (spacing.eq.0) then
    let true_spacing max(&1%max,abs(&1%min))|10
 endif
 levels true_spacing to &1%max by  true_spacing - 
       -true_spacing to &1%min by -true_spacing
endif