imageloadfont give error in GD library

$string = 'abcdefg+hijk';
$fontg=imageloadfont("fontnew.gdf");
$image = @imagecreate(200, 230);
$black = imagecolorallocate($image, 0, 0, 0); //background
$white = imagecolorallocate($image, 255, 255, 255);
imagestring($image,$fontg , 1, 1,  $string, $white);
imagepng($image);
imagedestroy($image);

Warning: imageloadfont() [function.imageloadfont]: gd warning: one parameter to a memory allocation multiplication is negative or zero, failing operation gracefully in imagec.php

Warning: imageloadfont() [function.imageloadfont]: Error reading font, invalid font header in imagec.php 

$white = imagecolorallocate($image, 255, 255, 255);
$font = 'font.ttf';
imagettftext($im, 20, 0, 11, 21, $white, $font, $text);