curl --header 'username:user' --header 'password:pass' http://myurl.com/image.png > image.png

header('Content-Type: image/png');
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://myurl.com/image.png');
curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
curl_setopt($ch, CURLOPT_USERPWD, 'user:pass');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$img = curl_exec($ch);
$imgcode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);
print($img);

header('Content-Type: image/png');
$headers = array('username:user','password:pass');
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://myurl.com/image.png');
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$img = curl_exec($ch);
$imgcode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);
print($img);