支持png透明图片的php生成缩略图类分享

PHP教程
<?php
  /*
   * desc: Resize Image(png,jpg,gif)
   * author: 十年后的卢哥哥
   * date: 2014.11.13
   */
  class ResizeImage {
    //图片类型
    private $type;
    //实际宽度
    private $width;
    //实际高度
    private $height;
    //改变后的宽度
    private $resize_width;
    //改变后的高度
    private $resize_height;
    //是否裁图
    private $cut;
    //源图象
    private $srcimg;
    //目标图象地址
    private $dstimg;
    //临时创建的图象
    private $im;
    function __construct($imgPath,$width,$height,$isCut,$savePath) {
      $this->srcimg = $imgPath;
      $this->resize_width = $width;
      $this->resize_height = $height;
      $this->cut = $isCut;
      //图片的类型
      $this->type = strtolower(substr(strrchr($this->srcimg,"."),1));
      //初始化图象
      $this->initi_img();
      //目标图象地址
      $this -> dst_img($savePath);
      //--
      $this->width = imagesx($this->im);
      $this->height = imagesy($this->im);
      //生成图象
      $this->newimg();
      ImageDestroy ($this->im);
    }
    private function newimg() {
      //改变后的图象的比例
      $resize_ratio = ($this->resize_width)/($this->resize_height);
      //实际图象的比例
      $ratio = ($this->width)/($this->height);
      if($this->cut) {
        //裁图
        $newimg = imagecreatetruecolor($this->resize_width,$this->resize_height);
        if($this->type=="png") {
          imagefill($newimg,imagecolorallocatealpha($newimg,127));
        }
        if($ratio>=$resize_ratio) {
          //高度优先
          imagecopyresampled($newimg,$this->im,$this->resize_width,$this->resize_height,(($this->height)*$resize_ratio),$this->height);
        } else {
          //宽度优先
          imagecopyresampled($newimg,$this->width,(($this->width)/$resize_ratio));
        }
      } else {
        //不裁图
        if($ratio>=$resize_ratio) {
          $newimg = imagecreatetruecolor($this->resize_width,($this->resize_width)/$ratio);
          if($this->type=="png") {
            imagefill($newimg,127));
          }
          imagecopyresampled($newimg,($this->resize_width)/$ratio,$this->height);
        } else {
          $newimg = imagecreatetruecolor(($this->resize_height)*$ratio,$this->resize_height);
          if($this->type=="png") {
            imagefill($newimg,($this->resize_height)*$ratio,$this->height);
        }
      }
      if($this->type=="png") {
        imagesavealpha($newimg,true);
        imagepng ($newimg,$this->dstimg);
      } else {
        imagejpeg ($newimg,$this->dstimg);
      }
    }
    //初始化图象
    private function initi_img() {
      if($this->type=="jpg") {
        $this->im = imagecreatefromjpeg($this->srcimg);
      }
      if($this->type=="gif") {
        $this->im = imagecreatefromgif($this->srcimg);
      }
      if($this->type=="png") {
        $this->im = imagecreatefrompng($this->srcimg);
      }
    }
    //图象目标地址
    private function dst_img($dstpath) {
      $full_length = strlen($this->srcimg);
      $type_length = strlen($this->type);
      $name_length = $full_length-$type_length;
      $name     = substr($this->srcimg,$name_length-1);
      $this->dstimg = $dstpath;
    }
  }
?>

PHP教程
<?php
  include "ResizeImage.php";
  //jpg
  $jpgResize = new ResizeImage("img/test_1920_1200.jpg",320,240,false,"img/test_320_240.jpg");
  //png
  $pngResize = new ResizeImage("img/test_1024_746.png","img/test_320_240.png");
?>