PHP生成缩略图,控制图片质量,支持.png .jpg .gif

namespace commoncomponents;

 class ResizeImageHelper
 {
     public $type;//图片类型
     public $width;//实际宽度
     public $height;//实际高度
     public $resize_width;//改变后的宽度
     public $resize_height;//改变后的高度
     public $cut;//是否裁图
     public $srcimg;//源图象
     public $dstimg;//目标图象地址
     public $im;//临时创建的图象
     public $quality;//图片质量
     public $img_array = array('jpg', 'png', 'gif');

     /**
      * 生成保持原图纵横比的缩略图，支持.png .jpg .gif
      * 缩略图类型统一为.png格式
      * $img     原图像文件名称
      * $wid     缩略图宽
      * $hei     缩略图高
      * $c       是否剪裁
      * $dstpath 缩略图文件名称，为空覆盖原图像文件
      * $quality 质量最大100
      * @return bool
      */
     public  function createThumbnail($img, $wid, $hei, $c, $dstpath, $quality = 100)
     {
         $this->srcimg = $img;
         $this->resize_width = $wid;
         $this->resize_height = $hei;
         $this->cut = $c;
         $this->quality = $quality;
         //$this->type=strtolower(substr(strrchr($this->srcimg,'.'),1));//图片的类型
         $this->type = $this->checkFileType($this->srcimg);//更为严格的检测图片类型
         if (!in_array($this->type, $this->img_array)) {
             return '';
         }
         $this->initi_img();//初始化图象
         $this->dst_img($dstpath);//目标图象地址
         $this->width = imagesx($this->im);
         $this->height = imagesy($this->im);
         $this->newimg();//生成图象
         ImageDestroy($this->im);
         return true;
     }

     private  function newimg()
     {
         $resize_ratio = ($this->resize_width) / ($this->resize_height);//改变后的图象的比例
         $ratio = ($this->width) / ($this->height);//实际图象的比例
         if (($this->cut) == '1') {//裁图
             if (function_exists('imagepng') && (str_replace('.', '', PHP_VERSION) >= 512)) {//针对php版本大于5.12参数变化后的处理情况
                 $quality = 9;
             }
             if ($ratio >= $resize_ratio) {//高度优先
                 $newimg = imagecreatetruecolor($this->resize_width, $this->resize_height);
                 imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, $this->resize_height, (($this->height) * $resize_ratio), $this->height);
                 imagejpeg($newimg, $this->dstimg, $this->quality);
             }
             if ($ratio < $resize_ratio) {//宽度优先
                 $newimg = imagecreatetruecolor($this->resize_width, $this->resize_height);
                 imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, $this->resize_height, $this->width, (($this->width) / $resize_ratio));
                 imagejpeg($newimg, $this->dstimg, $this->quality);
             }
         } else {//不裁图
             if ($ratio >= $resize_ratio) {
                 $newimg = imagecreatetruecolor($this->resize_width, ($this->resize_width) / $ratio);
                 imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, ($this->resize_width) / $ratio, $this->width, $this->height);
                 imagejpeg($newimg, $this->dstimg, $this->quality);
             }
             if ($ratio < $resize_ratio) {
                 $newimg = imagecreatetruecolor(($this->resize_height) * $ratio, $this->resize_height);
                 imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, ($this->resize_height) * $ratio, $this->resize_height, $this->width, $this->height);
                 imagejpeg($newimg, $this->dstimg, $this->quality);
             }
         }
     }

     private function initi_img()
     {//初始化图象
         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);
         }
     }

     private function dst_img($dstpath)
     {//图象目标地址
         $full_length = strlen($this->srcimg);
         $type_length = strlen($this->type);
         $name_length = $full_length - $type_length;
         $name = substr($this->srcimg, 0, $name_length - 1);
         $this->dstimg = $dstpath;
         //echo $this->dstimg;
     }

     //读取文件前几个字节 判断文件类型
     private function checkFileType($filename)
     {
         $file = fopen($filename, 'rb');
         $bin = fread($file, 2); //只读2字节
         fclose($file);
         $strInfo = @unpack("c2chars", $bin);
         $typeCode = intval($strInfo['chars1'] . $strInfo['chars2']);
         switch ($typeCode) {
             case 7790:
                 $fileType = 'exe';
                 break;
             case 7784:
                 $fileType = 'midi';
                 break;
             case 8297:
                 $fileType = 'rar';
                 break;
             case 255216:
                 $fileType = 'jpg';
                 break;
             case 7173:
                 $fileType = 'gif';
                 break;
             case 6677:
                 $fileType = 'bmp';
                 break;
             case 13780:
                 $fileType = 'png';
                 break;
             default:
                 $fileType = 'unknown' . $typeCode;
                 break;
         }
         if ($strInfo['chars1'] == '-1' && $strInfo['chars2'] == '-40') {
             return 'jpg';
         }
         if ($strInfo['chars1'] == '-119' && $strInfo['chars2'] == '80') {
             return 'png';
         }
         return $fileType;
     }

 }

调用示例

$resizeimage = new ResizeImageHelper();
$resizeimage->CreateThumbnail('path/../1.png', 1440,400, 1, 'path/../2.png', 80);