int
im_buildlut( DOUBLEMASK *input, IMAGE *output )
0 0
128 20
255 100
we generate the values:
index value
0 0
1 0.01
.. etc. linear interpolation
128 20
129 20.5
.. etc. linear interpolation
255 100
(we don’t generate the index column, that’s just there to show the position in the table)
The x/y points don’t need to be sorted: we do that. You can have several Ys: each becomes a band in the output LUT. X can start at any integer value, including negatives.