.TH IM_BUILDLUT 3 "June 2006"
.SH NAME
im_buildlut \- build a LUT from a set of x/y points
.SH SYNOPSIS
#include <vips/vips.h>

int
.br
im_buildlut( DOUBLEMASK *input, IMAGE *output )

.SH DESCRIPTION
.B im_buildlut(3)
constructs a LUT, interpolating a set of x/y points. Interpolation is strictly
piecewise linear. For example, if the input is:

  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. 

.SH RETURN VALUE
-1 on error, otherwise 0
.SH SEE ALSO
im_invertlut(3), im_identity(3).
.SH COPYRIGHT
2006, Imperial College