<?phpfunction ImageToJPG($srcFile,$dstFile,$towidth,$toheight){  $quality=80;  $data = @GetImageSize($srcFile);  switch ($data['2'])  {  case 1:    $im = imagecreatefromgif($srcFile);    break;  case 2:    $im = imagecreatefromjpeg($srcFile);    break;  case 3:    $im = imagecreatefrompng($srcFile);    break;  case 6:  $im = ImageCreateFromBMP( $srcFile );  break;  }  // $dstX=$srcW=@ImageSX($im);  // $dstY=$srcH=@ImageSY($im);  $srcW=@ImageSX($im);  $srcH=@ImageSY($im);  //$towidth,$toheight  if($toheight/$srcW > $towidth/$srcH){    $b = $toheight/$srcH;  }else{    $b = $towidth/$srcW;  }  //計算出圖片縮放后的寬高  // floor 舍去小數點部分，取整  $new_w = floor($srcW*$b);  $new_h = floor($srcH*$b);  $dstX=$new_w;  $dstY=$new_h;  $ni=@imageCreateTrueColor($dstX,$dstY);  @ImageCopyResampled($ni,$im,0,0,0,0,$dstX,$dstY,$srcW,$srcH);  @ImageJpeg($ni,$dstFile,$quality);  @imagedestroy($im);  @imagedestroy($ni);}//ImageToJPG('源文件名','目標文件名',目標寬,目標高);ImageToJPG('test2.png','test2.jpg',80,50);