支持png透明圖片的php生成縮略圖類分享

注：此功能依賴GD2圖形庫

最近要用php生成縮略圖，在網上找了一下，發現了這篇文章：PHP生成圖片縮略圖

試用了一下後，發現有這樣幾個問題：

1、png圖片生成的縮略圖是jpg格式的

2、png圖片生成的縮略圖沒有了透明（半透明）效果（填充了黑色背景）

3、代碼語法比較老

因此，在這個版本的基礎上簡單修改優化了一下。

PHP生成縮略圖類

<?php
  /*
   * desc: Resize Image(png, jpg, gif)
   * author: 十年後的盧哥哥
   * date: 2014.11.13
   */
  class ResizeImage {
    //圖片類型
    private $type;
    //實際寬度
    private $width;
    //實際高度
    private $height;
    //改變後的寬度
    private $resize_width;
    //改變後的高度
    private $resize_height;
    //是否裁圖
    private $cut;
    //源圖象
    private $srcimg;
    //目標圖象地址
    private $dstimg;
    //臨時創建的圖象
    private $im;

    function __construct($imgPath, $width, $height, $isCut, $savePath) {
      $this->srcimg = $imgPath;
      $this->resize_width = $width;
      $this->resize_height = $height;
      $this->cut = $isCut;
      //圖片的類型

      $this->type = strtolower(substr(strrchr($this->srcimg,"."),1));

      //初始化圖象
      $this->initi_img();
      //目標圖象地址
      $this -> dst_img($savePath);
      //--
      $this->width = imagesx($this->im);
      $this->height = imagesy($this->im);
      //生成圖象
      $this->newimg();
      ImageDestroy ($this->im);
    }

    private function newimg() {
      //改變後的圖象的比例
      $resize_ratio = ($this->resize_width)/($this->resize_height);
      //實際圖象的比例
      $ratio = ($this->width)/($this->height);
      if($this->cut) {
        //裁圖
        $newimg = imagecreatetruecolor($this->resize_width,$this->resize_height);
        if($this->type=="png") {
          imagefill($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));
        }
        if($ratio>=$resize_ratio) {
          //高度優先
          imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width,$this->resize_height, (($this->height)*$resize_ratio), $this->height);
        } else {
          //寬度優先
          imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, $this->resize_height, $this->width, (($this->width)/$resize_ratio));
        }
      } else {
        //不裁圖
        if($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);
      }
    }

    //初始化圖象
    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);
      }
    }

    //圖象目標地址
    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

使用時，直接調用類的構造函數即可，構造函數如下：

$resizeimage = new resizeimage($imgPath, $width, $height, $isCut, $savePath);

參數
$imgPath：原圖片地址

$width：縮略圖寬

$height：縮略圖高

$isCut：是否裁剪，bool值

$savePath：縮略圖地址（可以跟原圖片地址相同）

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