支持png透明图片的php生成缩略图类分享

注：此功能依赖gd2图形库

最近要用php生成缩略图，在网上找了一下，发现了这篇文章：php生成图片缩略图

试用了一下后，发现有这样几个问题：

1、png图片生成的缩略图是jpg格式的

2、png图片生成的缩略图没有了透明（半透明）效果（填充了黑色背景）

3、代码语法比较老

因此，在这个版本的基础上简单修改优化了一下。

php生成缩略图类

<?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      $this->type = strtolower篮球培训(substr(strrchr($this->srcimg,"."),1));      //初始化图象      $this->initi_img();      //目标图象地址      $thi2011重庆高考语文s -> dst_img($savepath);      //--      $this->width = imagesx($this->im);      $this->height = imagesy($this->im);      //生成图象      $this->newimg();  传媒经济    imagedestroy ($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($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));        }        if($ratio>=$resize_ratio) {          //高度优先          imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width,$this->resize_height, (($this->height)*$resize_ratio), $this->height);        } el {          //宽度优先          imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this-猪原由纪子>resize_width, $this->resize_height, $this->width, (($this->width)/$resize_ratio));        }      } el {        //不裁图        if($ratio>=$resize_ratio) {          $newimg = imagecreatetruecolor($this->resize_width,($this->resize_width)/$ratio);          if($this->type=="png") {            imagefill($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));          }          imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, ($this->resize_width)/$ratio, $this->width, $this->height);        } el {          $newimg = imagecreatetruecolor(($this->resize_height)*$ratio,$this->resize_height);          if($this->type=="png") {            imagefill($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));          }          imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, ($this->resize_height)*$ratio, $this->resize_height, $this->width, $this->height);        }      }      if($this->type=="png") {        imagesavealpha($newimg, true);        imagep国内医院排名ng ($newimg,$this->dstimg);      } el {        imagejpeg ($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,0,$name_length-1);      $this->dstimg = $dstpath;    }  }?>

使用

使用时，直接调用类的构造函数即可，构造函数如下：

$resizeimage = new resizeimage($imgpath, $width, $height, $iscut, $savepath);

参数
$imgpath：原图片地址

$width：缩略图宽

$height：缩略图高

$iscut：是否裁剪，bool值

$savepath：缩略图地址（可以跟原图片地址相同）

示例

<?php  include "resizeimage.php";  //jpg  $jpgresize = new resizeimage("img/test_1920_1200.jpg", 320, 240, fal, "img/test_320_240.jpg");  //png  $pngresize = new resizeimage("img/test_1024_746.png", 320, 240, fal, "img/test_320_240.png");?>

效果