Image::Compare::AVG_THRESHOLD - Compare two images by the overall average

Image-Compare documentation Contained in the Image-Compare distribution.

Index

Code Index:

NAME

Top

Image::Compare::AVG_THRESHOLD - Compare two images by the overall average color difference of their pixels.

OVERVIEW

Top

See the docs for Image::Compare for details on how to use this module. Further documentation is meant for those modifying or subclassing this comparator. See the documentation in Image::Compare::Comparator for general information about making your own comparator subclasses.

METHODS

Top

accumulate(\@pixel1, \@pixel2, $x, $y)

This method is called for each pixel in the two images to be compared. The difference between each pair of pictures is collected and stored for later use by get_result(). This method never short-circuits; when this comparator is used, all pixels are compared, every time.

$cmp->get_result()

Returns either the median or the arithmetic mean of the values collected by accumulate(), depending on the average type provided when this object was constructed.

AUTHOR

Top

Copyright 2008 Avi Finkel <avi@finkel.org>

This package is free software and is provided "as is" without express or implied warranty. It may be used, redistributed and/or modified under the terms of the Perl Artistic License (see http://www.perl.com/perl/misc/Artistic.html)

Image-Compare documentation Contained in the Image-Compare distribution. 
# Comparator for the "average threshold" comparison method.

package Image::Compare::AVG_THRESHOLD;

use warnings;
use strict;

use constant MEAN => 0;
use constant MEDIAN => 1;

use base qw/Image::Compare::Comparator/;

sub accumulate {
	my $self = shift;
	my $diff = $self->color_distance(@_);
	if ($self->{args}{type} == &MEAN) {
		$self->{count}++;
		$self->{sum} += $diff;
	}
	elsif ($self->{args}{type} == &MEDIAN) {
		push(@{$self->{scores}}, $diff);
	}
	else {
		die "Unrecognized average type: '$self->{args}{type}'";
	}
	return undef;
}

sub get_result {
	my $self = shift;
	my $val = 0;
	if ($self->{args}{type} == &MEAN) {
		$val = $self->{sum} / $self->{count};
	}
	elsif ($self->{args}{type} == &MEDIAN) {
		my @vals = sort @{$self->{scores}};
		if (@vals % 2) {
			# Return the middle value
			$val = $vals[(@vals / 2)];
		}
		else {
			# Return the mean of the middle two values
			$val  = $vals[ @vals / 2     ];
			$val += $vals[(@vals / 2) - 1];
			$val /= 2;
		}
	}
	return $val <= $self->{args}{value};
}

1;

__END__