ff-bright.1

.Dd 2024-03-29
.Dt FF-BRIGHT 1
.Os farbfeld-utils
.Sh NAME
.Nm ff-bright
.Nd farbfeld filter that add/multiply/exponent pixel values by a constant to adjust brightness
for one or more channels
.Sh SYNOPSIS
.Nm
<?channels?> <?add?> <?multiply?> <?exponent?>
.Sh DESCRIPTION
.Nm
reads a
.Xr farbfeld 5
image from stdin, applies adjust brightness by a constant and writes the result to stdout.
.Pp
It scales the values to the range 0 to 1, and then after applying the
specified arithmetic will clip to that range and expand back to a 16-bit
integer.
.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 first argument specifies which channels to affect; use one or more of the
letters r, g, b, and a. It is the only mandatory argument; the others are
optional.

Second argument is amount to add, default is 0.0. Greater than 0.0 will result
in a brighter image and less than 0.0 will result in a darker image.

Third argument is amount to multiply by, default to 1.0. Greater than 1.0 will
result in a brigher image and less than 1.0 will result in a darker image.

Fourth argument is amount to raise to the power of, default to 1.0. Greater
than 1.0 will result in a darker image and less than 1.0 will result in a
brighter image.

Order of operation is first exponent, and then multiply, and then add.
.Sh EXAMPLES
$
.Nm
rgb 0.25 < image.ff > image-bright.ff
.Pp
$
.Nm
rgb -0.25 < image.ff > image-dark.ff
.Pp
$
.Nm
g 0.0 1.1 < image.ff > image-green-hue.ff
.Pp
$
.Nm
b 0.0 1.0 0.04 < image.ff > image-blue-hue.ff
.Pp
$
.Nm
rb 0.0 1.0 0.4 < image.ff > image-increase-red-and-blue.ff
.Sh SEE ALSO
.Xr farbfeld 5 ,
.Xr farbfeld-utils 7