支援png透明圖片的php產生縮圖類分享_php技巧

註：此功能依賴GD2圖形庫

最近要用php產生縮圖，在網上找了一下，發現了這篇文章：PHP產生圖片縮圖

試用了一下後，發現有這樣幾個問題：

1、png圖片產生的縮圖是jpg格式的

2、png圖片產生的縮圖沒有了透明（半透明）效果（填充了黑色背景）

3、代碼文法比較老

因此，在這個版本的基礎上簡單修改最佳化了一下。

PHP產生縮圖類

<?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;    //靶心圖表象地址    private $dstimg;    //臨時建立的圖象    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();      //靶心圖表象地址      $this -> dst_img($savePath);      //--      $this->width = imagesx($this->im);      $this->height = imagesy($this->im);      //產生圖象      $this->newimg();      ImageDestroy ($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，直接調用類的建構函式即可，建構函式如下：

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

參數
$imgPath：原圖片地址

$width：縮圖寬

$height：縮圖高

$isCut：是否裁剪，bool值

$savePath：縮圖地址（可以跟原圖片地址相同）

樣本

<?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