| .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 |
