Obscure text by converting to a captcha-like image

obscure.php

<?php

$text = isset($_GET['t']) ? $_GET['t'] : '0.0000005';

$width = 140;
$height = 32;

$img = imagecreate(140, 32);

$white = imagecolorallocate($img, 255, 255, 255);
$black = imagecolorallocate($img, 0, 0, 0);
$text_color = imagecolorallocate(
    $img, mt_rand(0, 200), mt_rand(0, 200), mt_rand(0, 200)
);

$size = mt_rand(19, 20);
$angle = mt_rand(-2, 2);
$x = 2;
$y = $height - 9;
$font = './fonts/Lato-Reg.ttf';
imagettftext($img, $size, $angle, $x, $y, $text_color, $font, $text);

// The image on the external site allocates an extra color for anti-aliasing.
// Manually allocate it here to make the palette size match.
$unknown_color = imagecolorallocate(
    $img, mt_rand(0, 200), mt_rand(0, 200), mt_rand(0, 200)
);

# Create 5 random lines.
for ($i = 1; $i <= 5; $i++) {
    $color = imagecolorallocate(
        $img, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255)
    );
    $x1 = mt_rand(0, $width); $y1 = mt_rand(0, $height);
    $x2 = mt_rand(0, $width); $y2 = mt_rand(0, $height);
    imagesetthickness($img, 2);
    imageline($img, $x1, $y1, $x2, $y2, $color);
}

header('Content-Type: image/png');
imagepng($img);

imagedestroy($img);

?>