如何把一副大的图片变成filesize小一些的图片？

 1   
 2Header("Content-type: image/jpeg");   
 3dl("php_gd.dll");   
 4$n=6;   
 5$im = imagecreatefromJPEG('welcome.jpg');   
 6$im2 = imagecreate(imagesx($im)/$n,imagesy($im)/$n);   
 7$white = ImageColorAllocate($im2, 255,255,255);   
 8imagecolortransparent($im2,$white);   
 9  
10imagecopyresized($im2,$im,0,0,0,0,imagesx($im)/$n,imagesy($im)/$n,imagesx($im),imagesy($im));   
11ImageJPEG($im2);   
12ImageDestroy($im);   

1<img border="0" onload="if(this.clientWidth&gt;100)this.width=100; this.style.display=''" src="http://www.csdn.net/images/csdn.gif" style="display: none"/>