Imager::Fountain.3pm

Langue: en

Autres versions - même langue

Version: 2010-04-12 (ubuntu - 24/10/10)

Section: 3 (Bibliothèques de fonctions)

Sommaire

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:
•
"start" - the start position in the gradient where this segment takes effect between 0 and 1. Default: 0.
•
"middle" - the mid-point of the transition between the 2 colors, between 0 and 1. Default: average of "start" and "end".
•
"end" - the end of the gradient, from 0 to 1. Default: 1.
•
"c0" - the color of the fountain fill where the fill parameter is equal to start. Default: opaque black.
•
"c1" - the color of the fountain fill where the fill parameter is equal to end. Default: opaque black.
•
"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:

•
"linear"
•
"curved" - unimplemented so far.
•
"sine"
•
"sphereup"
•
"spheredown"
•
"color" - the way in which the color transitions between "c0" and "c1". Default: direct.

This can take any of the following values:

•
"direct" - each channel is simple scaled between c0 and c1.
•
"hueup" - the color is converted to a HSV value and the scaling is done such that the hue increases as the fill parameter increases.
•
"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)