使用PHP实现生成固定大小图片缩略图功能（智能裁剪，图片不失真）

<?php//图像处理类class Image { private $file;    //图片地址 private $width;   //图片长度 private $height;   //图片长度 private $type;    //图片类型 private $img;    //原图的资源句柄 private $new;    //新图的资源句柄  //构造方法，初始化 public function __construct($_file) {  $this->file = $_SERVER["DOCUMENT_ROOT"].$_file;  list($this->width, $this->height, $this->type) = getimagesize($this->file);  $this->img = $this->getFromImg($this->file, $this->type); } //缩略图(固定长高容器，图像等比例，扩容填充，裁剪)[固定了大小，不失真，不变形] public function thumb($new_width = 0,$new_height = 0) {    if (empty($new_width) && empty($new_height)) {   $new_width = $this->width;   $new_height = $this->height;  }    if (!is_numeric($new_width) || !is_numeric($new_height)) {   $new_width = $this->width;   $new_height = $this->height;  }    //创建一个容器  $_n_w = $new_width;  $_n_h = $new_height;    //创建裁剪点  $_cut_width = 0;  $_cut_height = 0;    if ($this->width < $this->height) {   $new_width = ($new_height / $this->height) * $this->width;  } else {   $new_height = ($new_width / $this->width) * $this->height;  }         if ($new_width < $_n_w) { //如果新高度小于新容器高度   $r = $_n_w / $new_width; //按长度求出等比例因子   $new_width *= $r; //扩展填充后的长度   $new_height *= $r; //扩展填充后的高度   $_cut_height = ($new_height - $_n_h) / 2; //求出裁剪点的高度  }    if ($new_height < $_n_h) { //如果新高度小于容器高度   $r = $_n_h / $new_height; //按高度求出等比例因子   $new_width *= $r; //扩展填充后的长度   $new_height *= $r; //扩展填充后的高度   $_cut_width = ($new_width - $_n_w) / 2; //求出裁剪点的长度  }       $this->new = imagecreatetruecolor($_n_w,$_n_h);  imagecopyresampled($this->new,$this->img,0,0,$_cut_width,$_cut_height,$new_width,$new_height,$this->width,$this->height); }  //加载图片，各种类型，返回图片的资源句柄 private function getFromImg($_file, $_type) {  switch ($_type) {   case 1 :    $img = imagecreatefromgif($_file);    break;   case 2 :    $img = imagecreatefromjpeg($_file);    break;   case 3 :     $img = imagecreatefrompng($_file);    break;   default:    Tool::alertBack('警告：此图片类型本系统不支持！');  }  return $img; }  //图像输出 public function out() {  imagepng($this->new,$this->file);  imagedestroy($this->img);  imagedestroy($this->new); }} ?> //使用方法：$_path = 'd:/1.jpg';$_img = new Image($_path);//$_path为图片文件的路径 $_img->thumb(150, 100); $_img->out();