PHP原比例生成縮略圖

<?php
$image = "jiequ.jpg"; // 原圖
$imgstream = file_get_contents($image);
$im = imagecreatefromstring($imgstream);
$x = imagesx($im);//獲取圖片的寬
$y = imagesy($im);//獲取圖片的高

// 縮略后的大小
$xx = 140;
$yy = 200;
if($x>$y){
//圖片寬大于高
    $sx = abs(($y-$x)/2);
    $sy = 0;
    $thumbw = $y;
    $thumbh = $y;
} else {
//圖片高大于等于寬
    $sy = abs(($x-$y)/2.5);
    $sx = 0;
    $thumbw = $x;
    $thumbh = $x;
  }
if(function_exists("imagecreatetruecolor")) {
  $dim = imagecreatetruecolor($yy, $xx); // 創建目標圖gd2
} else {
  $dim = imagecreate($yy, $xx); // 創建目標圖gd1
}
imageCopyreSampled ($dim,$im,0,0,$sx,$sy,$yy,$xx,$thumbw,$thumbh);
header ("Content-type: image/jpeg");
imagejpeg ($dim, false, 100);
?></pre>