NAME

Image::Quantize - quantize image data into 256 or fewer colours

SYNOPSIS

    use Image::Quantize;

DESCRIPTION

Image::Quantize reduces the number of colours used by an image to 256 or less. The reduction in the number of colours, also known as "quantization" or "palettization", reduces the size of the image.

METHODS

new

    Image::Quantize->new

This creates a new Image::Quantize object which can be fed image data.

It may be called with the same options as "set":

    Image::Quantize->new (max_colors => 42);

set

All setters can be accessed like this:

     $quantizer->set (dithering_level => $y);

get

All getters can be accessed like this:

     my $dl = $quantizer->get ('dithering_level');

max_colors

    $quantizer->max_colors ($x)

This sets the maximum possible number of colours which may be used in quantizing image data.

quality

    $quantizer->quality ($min, $max)

This sets the quality to $min and $max.

Get the quality:

    my ($min, $max) = $quantizer->quality ();

Internally this calls `liq_set_quality` and `liq_get_quality`.

dithering_level

    $quantizer->dithering_level ($x)

This overrides the default dithering level.

default_dithering_level

    $quantizer->default_dithering_level ();

Restores the default dithering level if it has been altered with "dithering_level". The default dithering depends on the speed chosen. The default speed is 3.

speed

Set the speed:

    $quantizer->speed ($x)

Get the speed:

    my $speed = $quantizer->speed ();

This sets the speed of quantization. The default speed is 3, and the value of the speed is an integer from 1 to 10.

min_opacity

    $quantizer->min_opacity ($x)

calls `liq_set_min_opacity`.

min_posterization

    $quantizer->min_posterization ($x)

Set the minimum posterization.

quantization_error

    my $qe = $quantizer->quantization_error ()

Get the quantization error.

output_gamma

    $quantizer->output_gamma ($x)

Set the output gamma. Called without argument it returns the output gamma:

     my $gamma = $quantizer->output_gamma ();

quantize

This is the main routine. It's subclassed by each image type.

quantize_file

     $quantizer->quantize_file (in => 'in.png', out => 'out.png');

Quantize the file specified by in to the file specified by out.

All of the setters can be added as options after `$png`:

    my $qpng = $quantizer->quantize ($png, dithering_level => $y);

set_log_callback

Logging can be handled like

    sub do_something
    {
           my ($message, $user_data) = @_;
    }
    $quantizer->set_log_callback (\& do_something);

and cancelled with

    $quantizer->set_log_callback ();

Image::Quantize is a base class, and then a subclass Image::Quantize::PNG handles PNG images. No other image types are currently planned. Image::Quantize::PNG is bundled into Image::Quantize, and uses Image::PNG::Libpng objects for reading and writing as shown in the synopsis above.

AUTHOR

Ben Bullock, <bkb@cpan.org>

COPYRIGHT & LICENCE

The Perl parts of this distribution are Copyright (C) 2014 by Ben Bullock and may be used, distributed, modified under the same terms as Perl itself. All the files in the distribution ending in .c and .h are part of libimagequant except for image-quantize-perl.c and are under the following copyright licence.

The copyright statement for libimagequant is as follows:

Copyright (C) 1989, 1991 by Jef Poskanzer. Copyright (C) 1997, 2000, 2002 by Greg Roelofs; based on an idea by Stefan Schneider. Copyright 2009-2013 by Kornel Lesinski.

Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. This software is provided "as is" without express or implied warranty.

cpanm Image::Quantize

perl -MCPAN -e shell
install Image::Quantize