# --------------------------------------------------------------------------------------------- 
# 
# compute_rgb_distance 
# 
# Given two RGB colors compute the distance between them by considering them as points 
# in 3 dimensions and calculating the distance between them (or equivalently the length 
# of a vector between them) 
# 
# $left          One color 
# $right         The other color 
# 
# --------------------------------------------------------------------------------------------- 
sub compute_rgb_distance 
{ 
    my ( $self, $left, $right ) = @_; 
 
    # Figure out where the left color is and then subtract the right 
    # color (point from it) to get the vector 
 
    $left =~ /^(..)(..)(..)$/; 
    my ( $rl, $gl, $bl ) = ( hex($1), hex($2), hex($3) ); 
 
    $right =~ /^(..)(..)(..)$/; 
    my ( $r, $g, $b ) = ( $rl - hex($1), $gl - hex($2), $bl - hex($3) ); 
 
    # Now apply Pythagoras in 3D to get the distance between them, we return 
    # the int because we don't need decimal level accuracy 
 
    return int( sqrt( $r*$r + $g*$g + $b*$b ) ); 
} 
 
# --------------------------------------------------------------------------------------------- 
# 
# compute_html_color_distance 
# 
# Calls compute_rgb_distance to set up htmlcolordistance__ from the current HTML back and 
# font colors 
# 
# --------------------------------------------------------------------------------------------- 
sub compute_html_color_distance 
{ 
    my ( $self ) = @_; 
 
    $self->{htmlcolordistance__} = $self->compute_rgb_distance( $self->{htmlfontcolor__}, $self->{htmlbackcolor__} ); 
}