function zbytscl,a,min1,max1,min=min,max=max
amax = max(a,min=amin,/nan)

if not isvalid(min1) then min1 = 0
if not isvalid(max1) then max1 = 100

if not isvalid(min) then min = min1
if not isvalid(max) then max = max1

arange = amax - amin

alow = amin + (arange * (0.01 * min))
ahi  = amin + (arange * (0.01 * max))

return, bytscl(a,min=alow,max=ahi)

en