#!/usr/bin/perl

#
# stupid thing to try and compress the output of
# gif2html (http://www.illuminated.co.uk/gif2html/)
# by making more use of stylesheets for colouring
# it seemed like a good idea at the time.
#
# howie@thingy.com  http://wotsit.thingy.com/haj/
# 23rd January 2001

# Update Jan 26th:
# Tweaked to name the classes a little more compactly
# for the first 3224 colours - saves an additional 3226 bytes on
# my test image (91825 original -> 78309 first version -> 75043 now)
#

use Text::Wrap qw(wrap $columns $huge);
$columns = 132;

$source = shift;

# First pass through, we'll collect up the colour stats.
# This might take a lot of memory!

# I'm going to assume that the input will have one bgcolor per line,
# because that's how it is right now, and I'm lazy.
# lines contain: bgcolor="#ffffff"
open(INPUT,$source) || die("Failed to open input file: $!");
while(<INPUT>)
{
	if (m/bgcolor="#(\w\w\w\w\w\w)"/)
	{	
		$colourcounts{$1}++;
		$lines++;
	}
}
close(INPUT);

# find the most popular colours
@mostcolours = sort {$colourcounts{$b} <=> $colourcounts{$a}} keys %colourcounts;

print "$lines lines checked.\n";
$totalsavings = 0;
$compressed=0;

$i=0;
$style_head="";

foreach $colour (@mostcolours)
{
	$frequency = $colourcounts{$colour};

	$classname = get_class_name($i);
	$stylesheet_replacement = sprintf("TD.%s{background:#%s;} ",$classname,$colour);
	$body_replacement = 'class="'.$classname.'"';
	
	$current_cost = length('bgcolor="#ffffff"') * $frequency;
	$new_cost = length($stylesheet_replacement) + length($body_replacement);
	$saving = $current_cost - $new_cost;

	if($saving > 0)
	{
		$totalsavings+=$saving;
		$replace{$colour}=$body_replacement;
		$style_head .= $stylesheet_replacement;
		$compressed++;
	}

	print "$i: $frequency: $colour: $saving\n";
	$i++;
}

print "saved $totalsavings with stylesheet, in total!\n";
print "$i colours in use, $compressed colours were packed\n";

$output = "";
# now we implement our decisions
open(INPUT,$source) || die("Failed to open input file: $!");
while(<INPUT>)
{
	chomp;chomp;
	if(m/-->/)
	{
		$output .= "\n".wrap("","",$style_head);
	}
	if (m/bgcolor="#(\w\w\w\w\w\w)"/)
	{	
		$colour=$1;
		if($replace{$colour} ne "")
		{
			s/bgcolor="#$colour"/$replace{$colour}/;
		}
	}
	$output .= $_;
}
close(INPUT);

open(OUTPUT,">".$source.".new") || die("Failed to create output file: $!");
print OUTPUT wrap("","",$output);
close(OUTPUT);



sub
get_class_name
{
	my $count = shift;

	my ($first,$second);

	my $firstpos = "abcdefghijklmnopqrstuvwxyzABCEDEFGHIJKLMNOPQRSTUVWXYZ";
	my $subseqpos = "0123456789abcdefghijklmnopqrstuvwxyzABCEDEFGHIJKLMNOPQRSTUVWXYZ";

	my $nfpos = length($firstpos);
	my $nspos = length($subseqpos);

	my $max2digit = $nfpos * $nspos;

	my $classname="";
	
	if($count < $nfpos)
	{
		$classname = substr($firstpos,$i,1);
	}
	else
	{	
		if($count <$max2digit)
		{
			$first = int($count/$nspos);
			$second = $count - ($first*$nspos);

			$classname = substr($firstpos,$first,1).substr($subseqpos,$second,1);
		}
		else
		{	
			# fall back to previous scheme - if you get this far, the image is either very complex or HUGE - you won't miss it
			$classname = sprintf("s%x",$count);
		}
	}
	return $classname;
}