生成图片缩略图类或者说任意缩放图片代码,PHP代码库,德仔网

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【PHP】生成图片缩略图类或者说任意缩放图片
作者:yllen / 发布于2013/7/19/ 888

	<?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;
	 }
	 }
	}
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