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



      $this->type = strtolower(substr(strrchr($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($newimg, 0, 0, imagecolorallocatealpha($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);

        } else {

          //宽度优先

          imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, $this->resize_height, $this->width, (($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($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));

          }

          imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, ($this->resize_width)/$ratio, $this->width, $this->height);

        } else {

          $newimg = imagecreatetruecolor(($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);

        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,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, false, "img/test_320_240.jpg");



  //png

  $pngResize = new ResizeImage("img/test_1024_746.png", 320, 240, false, "img/test_320_240.png");



?>







效果