Perl terminal Script which calculates the difference between two colors in percentages and generates a prepared scale-color SASS function.

colordiff

#!/usr/bin/perl

if ($#ARGV != 1) {
  print "usage: colordiff color_a color_b\n";
  exit;
}

$color_a = $ARGV[0];
$color_b = $ARGV[1];

$color_a_red = hex(substr($color_a, 0, 2));
$color_a_green = hex(substr($color_a, 2, 2));
$color_a_blue = hex(substr($color_a, 4, 2));

$color_b_red = hex(substr($color_b, 0, 2));
$color_b_green = hex(substr($color_b, 2, 2));
$color_b_blue = hex(substr($color_b, 4, 2));

printf( "scale-color(#%s, \$red: %.2f\%, \$green: %.2f\%, \$blue: %.2f\%)\n", 
        "$color_a",
        channel_difference($color_a_red, $color_b_red),
        channel_difference($color_a_green, $color_b_green),
        channel_difference($color_a_blue, $color_b_blue));

sub channel_difference{
  ($color_a, $color_b) = @_;

  if ($color_a > $color_b){
    my $basis = $color_a;
    my $diff = $color_a - $color_b;
    my $percent_diff = -($diff / ($basis / 100));
    return $percent_diff;
  } elsif ($color_a < $color_b) {
    my $basis = 255 - $color_a;
    my $diff = $color_b - $color_a;
    my $percent_diff = $diff / ($basis / 100);
    return $percent_diff;
  } 
  return 0;
}