PHP生成缩略图的类

浅见池也

<?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();
?>