PHP不加载ttf

Question

此脚本适用于localhost（Windows），但不适用于服务器（Debian）：

我已经上传了1：1的文件。请帮帮我，谢谢：）

<?php
function red_rectangle($img_src,$x1,$y1,$x2,$y2,$tr, $user)
{
// Load image
$img = imagecreatefrompng($img_src);

// Transparent red
$red = imagecolorallocatealpha($img, 0, 0, 0, $tr);

// Draw a white rectangle
imagefilledrectangle($img, $x1, $y1, $x2, $y2, $red);

$white = ImageColorAllocate ($img, 255, 255, 255);
ImageTTFText ($img, 35, 0, 15, 350, $white, "Big.ttf", 
              $user);
// Don't forget to output a correct header
header('Content-Type: image/jpg');

// Save the image (overwrite)
imagepng($img);
imagedestroy($img);
}
$img_src = 'playerimages/streamnew.png';
$box = imagettfbbox ( 35 , 0 , "Big.ttf" , $_GET['username'] );
$width = abs($box[4] - $box[0]);
$height = abs($box[5] - $box[1]);
$x1= 10;
$y1= 310;
$x2 = 25+$width;
$y2=360;
red_rectangle($img_src,$x1,$y1,$x2,$y2,50, $_GET['username']);
?>

回答：$ _SERVER ['DOCUMENT_ROOT']。“/ big.ttf”