PHP Captcha Image can not be displayed because of errors - php

Question

This is my static function in class 'image_utils.php'
public static function getCaptcha()
{
try {
$width = 200;
$height = 30;
$font = 'fonts/arial.ttf';
//
if (!file_exists($font)) {
throw new Exception('Error Font not found');
}
//
$image = imagecreatetruecolor($width, $height);
$white = imagecolorallocate($image, 255, 255, 255);
$grey = imagecolorallocate($image, 180, 180, 180);
$black = imagecolorallocate($image, 0, 0, 0);
//
for ($sq = 1; $sq <= 10; $sq++) {
$cx = (int)rand(0, $width / 2);
$cy = (int)rand(0, $height);
$h = $cy + (int)rand(0, $height / 5);
$w = $cx + (int)rand($width / 3, $width);
if (!imagefilledrectangle($image, $cx, $cy, $w, $h, $white)) {
throw new Exception('Error in White Fill');
}
}
//
$ellipse_count = 5;
for ($i = 0; $i < $ellipse_count; $i++) {
$cx = (int)rand(-1 * ($width / 2), $width + ($width / 2));
$cy = (int)rand(-1 * ($height / 2), $height + ($height / 2));
$h = (int)rand($height / 2, 2 * $height);
$w = (int)rand($width / 2, 2 * $width);
if (!imageellipse($image, $cx, $cy, $w, $h, $grey)) {
throw new Exception('Error in Grey Fill');
}
}
//
imagefttext($image, 20, 0, 10, 20, $black, $font, 'Captcha');
header('Content-type: image/png');
if (!imagepng($image)) {
throw new Exception('Error in ImagePng');
}
} catch (Exception $ex) {
echo $ex->getMessage();
}
}
Calling it in 'log.php' in img tag:
<img src='<?php image_utils::getCaptcha() ?>'/>
Gives an error 'The image cannot be displayed because it contains errors'. I have create a check for font file as shown in code so the font file is in inclusion. Please throw some light.
Thanks in Advance.