AIPS HELP file for FUNCTYPE in 31DEC18
As of Mon Nov 19 13:46:43 2018
Type: Adverb (String, 2 characters)
Use: The function type associated with a task or a verb. The function
is designated by two characters.
For image loading transfer functions the usual values are
'LN' for linear, -> x
'LG' for logarithmic, -> log10 (1+9*x)
'L2' for extra logarithmic -> log10 (1+99*x) / 2
'SQ' for square root, -> sqrt (x)
'NE' for negative linear, -> 1 - x
'NG' for negative logarithmic, -> log10 (10 - 9*x)
'N2' for negative extra logarithmic -> log10 (100-99*x) / 2
'NQ' for negative square root. -> sqrt (1-x)
where x is between 0 and 1 and is usually taken from
x = (Map(i,j) - Pixr(1)) / (Pixr(2) - Pixr(1))
x = max (0, min (1, x))
Unrecognized codes are taken as 'LN'.
Null value: ' '
Null value assignment varies with task or verb.