ff-channel.1

.Dd 2024-04-03
.Dt FF-CHANNEL 1
.Os farbfeld-utils
.Sh NAME
.Nm ff-channel
.Nd farbfeld filter that combines channels from four farbfeld pictures
.Sh SYNOPSIS
.Nm
<file> <file> <?file?> <?file?>
.Sh DESCRIPTION
.Nm
combines channels from four
.Xr farbfeld 5
pictures and writes the result to stdout.
.Pp
No data is read from stdin.
.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 four pictures as command-line arguments, all of which must be
the same size.

The output picture takes:
   - the red channel from the first input
   - the green channel from the second input
   - the blue channel from the third input and
   - the alpha channel from the fourth input

An alternative invocation is to provide only two pictures as command-line
arguments. In this case, the red and green and blue channels come from the
first picture, and the alpha channel comes from the second picture.
.Sh EXAMPLES
$
.Nm
red.ff green.ff blue.ff alpha.ff > channels-combined.ff
.Pp
$
.Nm
rgb.ff alpha.ff > channels-combined.ff
.Sh SEE ALSO
.Xr farbfeld 5 ,
.Xr farbfeld-utils 7