Imager::Fountain(3pm)

NAME

Imager::Fountain - a class for building fountain fills suitable for use by

the fountain filter.

SYNOPSIS

use Imager::Fountain;
my $f1 = Imager::Fountain->read(gimp=>$filename);
$f->write(gimp=>$filename);
my $f1 = Imager::Fountain->new;
$f1->add(start=>0, middle=>0.5, end=>1.0,
         c0=>Imager::Color->new(...),
         c1=>Imager::Color->new(...),
         type=>$trans_type, color=>$color_trans_type);

DESCRIPTION

Provide an interface to build arrays suitable for use by the Imager
fountain filter. These can be loaded from or saved to a GIMP gradient file or you can build them from scratch.

read(gimp=>$filename)
read(gimp=>$filename, name=>\$name)

Loads a gradient from the given GIMP gradient file, and returns a
new Imager::Fountain object.

If the name parameter is supplied as a scalar reference then any
name field from newer GIMP gradient files will be returned in it.

my $gradient = Imager::Fountain->read(gimp=>'foo.ggr');
my $name;
my $gradient2 = Imager::Fountain->read(gimp=>'bar.ggr', name=>\$name);

write(gimp=>$filename)
write(gimp=>$filename, name=>$name)

Save the gradient to a GIMP gradient file.

The second variant allows the gradient name to be set (for newer
versions of the GIMP).

$gradient->write(gimp=>'foo.ggr')

or die Imager->errstr;

$gradient->write(gimp=>'bar.ggr', name=>'the bar gradient')

or die Imager->errstr;

new Create an empty fountain fill description.

add(start=>$start, middle=>$middle, end=>1.0, c0=>$start_color,
c1=>$end_color, type=>$trans_type, color=>$color_trans_type)

Adds a new segment to the fountain fill, the possible options are:

o "start" - the start position in the gradient where this segment

takes effect between 0 and 1. Default: 0.

o "middle" - the mid-point of the transition between the 2

colors, between 0 and 1. Default: average of "start" and
"end".

o "end" - the end of the gradient, from 0 to 1. Default: 1.

o "c0" - the color of the fountain fill where the fill parameter

is equal to start. Default: opaque black.

o "c1" - the color of the fountain fill where the fill parameter

is equal to end. Default: opaque black.

o "type" - the type of segment, controls the way in which the

fill parameter moves from 0 to 1. Default: linear.

This can take any of the following values:

o "linear"

o "curved" - unimplemented so far.

o "sine"

o "sphereup"

o "spheredown"

o "color" - the way in which the color transitions between "c0"

and "c1". Default: direct.

This can take any of the following values:

o "direct" - each channel is simple scaled between c0 and c1.

o "hueup" - the color is converted to a HSV value and the

scaling is done such that the hue increases as the fill
parameter increases.

o "huedown" - the color is converted to a HSV value and the

scaling is done such that the hue decreases as the fill
parameter increases.

In most cases you can ignore some of the arguments, eg.

# assuming $f is a new Imager::Fountain in each case here
use Imager ':handy';
# simple transition from red to blue
$f->add(c0=>NC('#FF0000'), c1=>NC('#0000FF'));
# simple 2 stages from red to green to blue
$f->add(end=>0.5, c0=>NC('#FF0000'), c1=>NC('#00FF00'))
$f->add(start=>0.5, c0=>NC('#00FF00'), c1=>NC('#0000FF'));

simple(positions=>[ ... ], colors=>[...])

Creates a simple fountain fill object consisting of linear
segments.

The array references passed as positions and colors must have the
same number of elements. They must have at least 2 elements each.

colors must contain Imager::Color or Imager::Color::Float objects.

eg.

my $f = Imager::Fountain->simple(positions=>[0, 0.2, 1.0],

colors=>[ NC(255,0,0), NC(0,255,0),

NC(0,0,255) ]);

Implementation Functions

Documented for internal use.

_load_gimp_gradient($class, $fh, $name)

Does the work of loading a GIMP gradient file.

_save_gimp_gradient($self, $fh, $name)

Does the work of saving to a GIMP gradient file.

FILL PARAMETER

The add() documentation mentions a fill parameter in a few places, this is as good a place as any to discuss it.

The process of deciding the color produced by the gradient works
through the following steps:

1. calculate the base value, which is typically a distance or an angle

of some sort. This can be positive or occasionally negative,
depending on the type of fill being performed (linear, radial,
etc).

2. clamp or convert the base value to the range 0 through 1, how this is done depends on the repeat parameter. I'm calling this result
the fill parameter.

3. the appropriate segment is found. This is currently done with a
linear search, and the first matching segment is used. If there is no matching segment the pixel is not touched.

4. the fill parameter is scaled from 0 to 1 depending on the segment
type.

5. the color produced, depending on the segment color type.

AUTHOR

Tony Cook <tony@develop-help.com>

SEE ALSO

Imager(3)

perl v5.10.1 2010-04-12 Imager::Fountain(3pm)