PHP原比例生成缩略图

<?php
$image = "jiequ.jpg"; // 原图
$imgstream = file_get_contents($image);
$im = imagecreatefromstring($imgstream);
$x = imagesx($im);//获取图片的宽
$y = imagesy($im);//获取图片的高

// 缩略后的大小
$xx = 140;
$yy = 200;

if($x>$y){
//图片宽大于高
    $sx = abs(($y-$x)/2);
    $sy = 0;
    $thumbw = $y;
    $thumbh = $y;
} else {
//图片高大于等于宽
    $sy = abs(($x-$y)/2.5);
    $sx = 0;
    $thumbw = $x;
    $thumbh = $x;
  }
if(function_exists("imagecreatetruecolor")) {
  $dim = imagecreatetruecolor($yy, $xx); // 创建目标图gd2
} else {
  $dim = imagecreate($yy, $xx); // 创建目标图gd1
}
imageCopyreSampled ($dim,$im,0,0,$sx,$sy,$yy,$xx,$thumbw,$thumbh);
header ("Content-type: image/jpeg");
imagejpeg ($dim, false, 100);
?>