ff-false.1

.Dd 2024-05-05
.Dt FF-FALSE 1
.Os farbfeld-utils
.Sh NAME
.Nm ff-false
.Nd farbfeld filter that that changes colours in the picture to a specified gradient
.Sh SYNOPSIS
.Nm
<0> <colour> <#> <colour> ... <255>
.Sh DESCRIPTION
.Nm
reads a
.Xr farbfeld 5
image from stdin, applies the false filter and writes the result to stdout.
.Pp
This farbfeld filter is used to change colours in the picture to a specified gradient.
.Pp
This is the 8-bit version of the false filter, for 16-bit gradients refer to
.Xr ff-false16 1 .
.Pp
In case of an error
.Nm
writes a diagnostic message to stderr.
.Sh EXIT STATUS
.Bl -tag -width Ds
.It 0
Image processed successfully.
.It 1
An error occurred.
.El
.Sh OPTIONS
The filter takes at a minimum five arguments.

Specify a gradient by a sequence alternating 8-bit numbers and colours, with
an 8-bit number as the first and last argument; these should be 0 and 255,
although it is not required. It represents a gradient with several components,
and interpolated in between. Changes colours of the picture to the
corresponding value of the channel of the gradient.

The colour can be defined through one of the following patterns:
   hh                one pair of 8-bit hex value (applies to all channels)
   hhhh              one pair of 16-bit hex value (applies to all channels)
   rrggbb            three pairs of 8-bit hex values
   rrggbbaa          four pairs of 8-bit hex values
   rrrrggggbbbb      three pairs of 16-bit hex values
   rrrrggggbbbbaaaa  four pairs of 16-bit hex values
.Sh EXAMPLES
$
.Nm
20 906060 40 609090 80 AACC23 255 < image.ff > false.ff
.Sh SEE ALSO
.Xr ff-false16 1 ,
.Xr farbfeld 5 ,
.Xr farbfeld-utils 7