PHP生成缩略图的类

<?php
/*
 * Thumbnail类  生成缩略图
 * 2010-09-08
 */

//自定义一组异常类，发生错误时自动抛出异常
class ThumbnailException extends Exception{
	public function __construct($message = null ,$code =0){
		parent::__construct($message ,$code);
		error_log('Error in '.$this->getFile(). 'line: '.$this->getLine().' Error: '.$this->getMessage());
	}
}
class ThumbnailFileException extends ThumbnailException{ }
class ThumbnailNotSupportedException extends ThumbnailException{ }

class Thumbnail{
      private $maxWidth;
      private $maxHeight;
      private $scale;
      private $inflate;
      private $types;
      private $imgLoaders;
      private $imgCreators;
      private $source;
      private $sourceWidth;
      private $sourceHeight;
      private $sourceMime;
      private $thumb;
      private $thumbWidth;
      private $thumbHeight;
/*
 * 构造函数 带4个参数 前两个参数分别是缩略图的最大像素宽度和最大像素高度  第三个参数设置是否按比例将图像缩小为缩略图 第四个参数设置处理小图像时 是否放大
 * $types 缩略图的图片类型
 * loadFile 允许指定一个装载的本地文件
 * loadData 同 loadFile   取得数据库中的字符串
 */
   public function __construct($maxWidth, $maxHeight, $scale = true,$inflate = true){
   	  $this->maxWidth = $maxWidth;
   	  $this->maxHeight = $maxHeight;
   	  $this->scale = $scale;
   	  $this->inflate = $inflate;

   	  $this->types = array('image/jpeg','image/png','image/gif');
   	  $this->imgLoaders = array(
            'image/jpeg' => 'imagecreatefromjpeg',
            'image/png' => 'imagecreatefrompng',
            'image/gif' => 'imagecreatefromgif'
   	  );
   	  $this->imgCreators = array('image/jpeg'=>'imagejpeg','image/png'=>'imagepng','image/gif'=>'imagegif');
   }

   public function loadFile($image){
   	if(!$dims = @getimagesize($image)){
   		throw new ThumbnailFileException('Could not find image: '.$image);
   	}
   	if(in_array($dims['mime'],$this->types)){
   		$loader = $this->imgLoaders[$dims['mime']];
   		$this->source  = $loader($image);
   		$this->sourceWidth = $dims[0];
   		$this->sourceHeight = $dims[1];
   		$this->sourceMime = $dims['mime'];
   		$this->initThumb();
   		return true;
   	}else{
   		throw new ThumbnailNotSupportedException('Image Mime type '.$dims['mime'].' not supported!');
   	}
   }

   public function loadData($image, $mime){
   	if(in_array($mime,$this->types)){
   		if($this->source = @imagecreatefromstring($image)){
   			$this->sourceWidth = imagesx($this->source);
   			$this->sourceHeight = imagesy($this->source);
   			$this->sourceMime =$mime;
   			$this->initThumb();
   			return true;
   		}else{
   			throw new ThumbnailFileException('Could not load image from string');
   		}
   	}else{
   		throw new ThumbnailNotSupportedException('Image Mine type '.$mime.' not supported');
   	}
   }

/*]
 * buildThumb()  生成缩略图的函数
 * getMime() 返回MIME类型  该类型可以为缩略图生成Content-type头
 * getThumbWidth() 返回缩略图的像素宽度
 * getThumbHeight() 返回缩略图的像素高度
 * 私有方法initThumb() 为类处理缩放功能
 */
   public function buildThumb($file = null){
   	$createor = $this->imgCreators[$this->sourceMime];
   	if(isset($file)){
   		return $createor($this->thumb, $file);
   	}else{
   		return $createor($this->thumb);
   	}
   }

   public function getMime(){
   	return $this->sourceMime;
   }

   public function getThumbWidth(){
   	return $this->thumbWidth;
   }
   public function getThumbHeight(){
   	return $this->thumbHeight;
   }
   private function initThumb(){
   	if($this->scale){
   		if($this->sourceWidth > $this->sourceHeight){
   			$this->thumbWidth = $this->maxWidth;
   			$this->thumbHeight = floor($this->sourceHeight * ($this->maxWidth / $this->sourceWidth));
   		}else if($this->sourceWidth < $this->sourceHeight){
   			$this->sourceHeight = $this->maxHeight;
   			$this->thumbWidth = floor($this->sourceWidth * ($this->maxHeight / $this->sourceHeight));
   		}else{
   			$this->thumbWidth = $this->maxWidth;
   			$this->thumbHeight = $this->maxHeight;
   		}
   	}
    // imagecreatetruecolor() 创建空白的缩略图
    $this->thumb = imagecreatetruecolor($this->thumbWidth, $this->thumbHeight);
    //将原图像复制到缩略图图像
    if($this->sourceWidth <= $this->maxWidth && $this->sourceHeight <= $this->maxHeight && $this->inflate == false){
    	$this->thumb = $this->source;
    }else{
    	imagecopyresampled( $this->thumb, $this->source, 0 ,0 , 0, 0, $this->thumbWidth, $this->thumbHeight, $this->sourceWidth, $this->sourceHeight);
    }
   }
}
?>

 测试效果

<?php
require_once('Thumbnail.class.php');
$tn = new Thumbnail( 200, 200);
$tn->loadFile('1.jpg');
header('Content-type: '.$tn->getMime());
$tn->buildThumb();
?>