PHP is used to realize the detailed method of scaling up and reducing images

    function resizeimage($srcfile,$mySize){
    $size=getimagesize($srcfile);
    switch($size[2]){
    case 1:
    $img=imagecreatefromgif($srcfile);
    break;
    case 2:
    $img=imagecreatefromjpeg($srcfile);
    break;
    case 3:
    $img=imagecreatefrompng($srcfile);
    break;
    }
    // Width and height of the source image 
    $oldImg['w']=imagesx($img);
    $oldImg['h']=imagesy($img);
    if ($oldImg['w']<=$mySize['w'] && $oldImg['h']<156){
    $rate=1;
    }elseif ($oldImg['w']>$mySize['w'] && $oldImg['h']<$mySize['h']){
    $rate=$mySize['w']/$oldImg['w'];
    }elseif ($oldImg['w']<$mySize['w'] && $oldImg['h']>$mySize['h']){
    $rate=$mySize['h']/$oldImg['h'];
    }elseif ($oldImg['w']>$mySize['w'] && $oldImg['h']>$mySize['h']){
    $rate1=$mySize['w']/$oldImg['w'];
    $rate2=$mySize['h']/$oldImg['h'];
    if ($rate1>$rate2){$rate=$rate2;}else{$rate=$rate1;}
    }
    $newImg['w']=$oldImg['w']*$rate;
    $newImg['h']=$oldImg['h']*$rate;
    return "width=".$newImg['w']." height=".$newImg['h'];
    } 

   $mySize=array('w'=>143,'h'=>156);
   $imgSize=resizeimage("22.jpg",$mySize);
   echo "<img src=\"22.jpg\"".resizeimage("22.jpg",$mySize)."/>";