<?php  /**   * @abstract 生成图片的缩略图，可以指定任意尺寸，生成的图片为png格式   * @example   * $file = 'test.png';   * $th =new Thumbnail();   * $th->GenerateThumbnail($file, 400, 500);   *   */  class Thumbnail{       /**       * @var string $from 源图片       */       private $from;       /**       * @var string $name 缩略图的文件名       */       private $name = '';       /**       * @var 原图宽       */       private $rWidth;       /**       * @var 原图高       */       private $rHeight;       /**       * @var 缩略图宽       */       private $tWidth;       /**       * @var 缩略图高       */       private $tHeight;       /**       * @var 实际缩放到的宽度       */       private $width;       /**       * @var 实际缩放到的高度       */       private $height;         public function __construct(){           try{               if(!function_exists('gd_info')){                   throw new Exception('Must GD extension is enabled');               }           }           catch(Exception $e){               $msg = 'class ' . __CLASS__ . ' Error:' . $e->getMessage();               echo $msg;               exit;           }       }       /**       * @var $from 原图像       * @var $width 生成的缩略图的宽       * @var $height 生成缩略图的高       * @var $name 生成的缩略图的文件名，不带后缀       * @return string 生成的缩略图       */       public function GenerateThumbnail($from, $width, $height, $name=''){           try{               if(!file_exists($from)){                   throw new Exception('File does not exist');               }               if($width <= 0){                   throw new Exception('The width is invalid');               }               if($height <= 0){                   throw new Exception('The height is invalid');               }               $this->from = $from;               $this->tWidth = $width;               $this->tHeight = $height;               if(!empty($name)){                   $this->name = $name;               }               else{                   $this->name = date('Ymd') . mt_rand(0, 9999);               }               $this->createThumbnail();           }           catch(Exception $e){               $msg = 'class ' . __CLASS__ . ' Error:' . $e->getMessage();               echo $msg;               exit;           }       }         public function getThumbnail(){           return $this->name;       }         /**       * 生成缩略图文件       */       private function createThumbnail(){           try{               //读取原始图像信息               $sourceInfo = getimagesize($this->from);               $this->rWidth = $sourceInfo[0];               $this->rHeight = $sourceInfo[1];               //创建缩略图图像资源句柄               $new_pic = imagecreatetruecolor($this->tWidth, $this->tHeight);               //原图绘制到缩略图的x、y坐标               $x = 0;               $y = 0;               //创建原始图像资源句柄               $source_pic = '';               switch ($sourceInfo[2]){                   case 1: $source_pic = imagecreatefromgif($this->from); //gif                           break;                   case 2: $source_pic = imagecreatefromjpeg($this->from); //jpg                           break;                   case 3: $source_pic = imagecreatefrompng($this->from); //png                           break;                   default: throw new Exception('Does not support this type of image');               }               //计算缩放后图像实际大小               //原图宽高均比缩略图大               if($this->rWidth > $this->tWidth && $this->rHeight > $this->tHeight){                   $midw = ($this->rWidth - $this->tWidth) / $this->rWidth; //宽缩小的比例                   $midh = ($this->rHeight - $this->tHeight) / $this->rHeight; //高缩小的比例                   //那个缩小的比例大以那个为准                   if($midw > $midh){                       $this->width = $this->tWidth;                       $this->height = $this->rHeight - floor($this->rHeight * $midw);                       $y = ($this->tHeight - $this->height) / 2;                   }                   else{                       $this->width = $this->rWidth - floor($this->rWidth * $midh);                       $this->height = $this->tHeight;                       $x = ($this->tWidth - $this->width) / 2;                   }               }               //原图宽高均比缩略图小               elseif($this->rWidth < $this->tWidth && $this->rHeight < $this->tHeight){                   $midw = ($this->tWidth - $this->rWidth) / $this->rWidth; //宽放大的比例                   $midh = ($this->tHeight - $this->rHeight) / $this->rHeight; //高放大的比例                   //那个放大的比例小以那个为准                   if($midw < $midh){                       $this->width = $this->tWidth;                       $this->height = $this->rHeight + floor($this->rHeight * $midw);                       $y = ($this->tHeight - $this->height) / 2;                   }                   else{                       $this->width = $this->rWidth + floor($this->rWidth * $midh);                       $this->height = $this->tHeight;                       $x = ($this->tWidth - $this->width) / 2;                   }               }               //原图宽小于缩略图宽，原图高大于缩略图高               elseif($this->rWidth < $this->tWidth && $this->rHeight > $this->tHeight){                   $mid = ($this->rHeight - $this->tHeight) / $this->rHeight; //高缩小的比例                   $this->width = $this->rWidth - floor($this->rWidth * $mid);                   $this->height = $this->rHeight - floor($this->rHeight * $mid);                   $x = ($this->tWidth - $this->width) / 2;                   $y = ($this->tHeight - $this->height) / 2;               }               //原图宽大于缩略图宽，原图高小于缩略图高               elseif($this->rWidth > $this->tWidth && $this->rHeight < $this->tHeight){                   $mid = ($this->rWidth - $this->tWidth) / $this->rWidth; //宽缩小的比例                   $this->width = $this->rWidth - floor($this->rWidth * $mid);                   $this->height = $this->rHeight - floor($this->rHeight * $mid);                   $x = ($this->tWidth - $this->width) / 2;                   $y = ($this->tHeight - $this->height) / 2;               }               else{                   throw new Exception('Resize error');               }                 //给缩略图添加白色背景               $bg = imagecolorallocate($new_pic, 255, 255, 255);               imagefill($new_pic, 0, 0, $bg);               //缩小原始图片到新建图片               imagecopyresampled($new_pic, $source_pic, $x, $y, 0, 0, $this->width, $this->height, $this->rWidth, $this->rHeight);               //输出缩略图到文件               imagepng($new_pic, $this->name.'.png');               imagedestroy($new_pic);               imagedestroy($source_pic);           }           catch(Exception $e){               $msg = 'class ' . __CLASS__ . ' Error:' . $e->getMessage();               echo $msg;               exit;           }       }  }