php生成圖片縮略圖類

 
<?php
/**


@abstract 生成圖片的縮略圖，可以指定任意尺寸，生成的圖片為png格式
@example
$file = 'test.png';
$th =new Thumbnail();
$th->GenerateThumbnail($file, 400, 500);
/
class Thumbnail{
  /**

@var string $from 源圖片
*/
private $from;
/**
@var string $name 縮略圖的文件名
*/
private $name = '';
/**
@var 原圖寬
*/
private $rWidth;
/**
@var 原圖高
*/
private $rHeight;
/**
@var 縮略圖寬
*/
private $tWidth;
/**
@var 縮略圖高
*/
private $tHeight;
/**
@var 實際縮放到的寬度
*/
private $width;
/**
@var 實際縮放到的高度
*/
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 原圖像
@var $width 生成的縮略圖的寬
@var $height 生成縮略圖的高
@var $name 生成的縮略圖的文件名，不帶后綴
@return string 生成的縮略圖
*/
public function GenerateThumbnail($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;
}
/**

生成縮略圖文件
*/
private function createThumbnail(){
  try{

  //讀取原始圖像信息
  $sourceInfo = getimagesize($this->from);
  $this->rWidth = $sourceInfo[0];
  $this->rHeight = $sourceInfo[1];
  //創建縮略圖圖像資源句柄
  $new_pic = imagecreatetruecolor($this->tWidth, $this->tHeight);
  //原圖繪制到縮略圖的x、y坐標
  $x = 0;
  $y = 0;
  //創建原始圖像資源句柄
  $source_pic = '';
  switch ($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');
  }
  //計算縮放后圖像實際大小
  //原圖寬高均比縮略圖大
  if($this->rWidth > $this->tWidth && $this->rHeight > $this->tHeight){
      $midw = ($this->rWidth - $this->tWidth) / $this->rWidth; //寬縮小的比例
      $midh = ($this->rHeight - $this->tHeight) / $this->rHeight; //高縮小的比例
      //那個縮小的比例大以那個為準
      if($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 - $this->width) / 2;
      }
  }
  //原圖寬高均比縮略圖小
  elseif($this->rWidth < $this->tWidth && $this->rHeight < $this->tHeight){
      $midw = ($this->tWidth - $this->rWidth) / $this->rWidth; //寬放大的比例
      $midh = ($this->tHeight - $this->rHeight) / $this->rHeight; //高放大的比例
      //那個放大的比例小以那個為準
      if($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 - $this->width) / 2;
      }
  }
  //原圖寬小于縮略圖寬，原圖高大于縮略圖高
  elseif($this->rWidth < $this->tWidth && $this->rHeight > $this->tHeight){
      $mid = ($this->rHeight - $this->tHeight) / $this->rHeight; //高縮小的比例
      $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 - $this->height) / 2;
  }
  //原圖寬大于縮略圖寬，原圖高小于縮略圖高
  elseif($this->rWidth > $this->tWidth && $this->rHeight < $this->tHeight){
      $mid = ($this->rWidth - $this->tWidth) / $this->rWidth; //寬縮小的比例
      $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');
  }

  //給縮略圖添加白色背景
  $bg = imagecolorallocate($new_pic, 255, 255, 255);
  imagefill($new_pic, 0, 0, $bg);
  //縮小原始圖片到新建圖片
  imagecopyresampled($new_pic, $source_pic, $x, $y, 0, 0, $this->width, $this->height, $this->rWidth, $this->rHeight);
  //輸出縮略圖到文件
  imagepng($new_pic, $this->name.'.png');
  imagedestroy($new_pic);
  imagedestroy($source_pic);

}
  catch(Exception $e){

  $msg = 'class ' . __CLASS__ . ' Error:' . $e->getMessage();
  echo $msg;
  exit;

}
}
}




</pre>