php如何正则表达式替换图片地址

<?php
/*PHP正则提取图片img标记中的任意属性*/
$str = '<center><img src="/uploads/images/20100516000.jpg" height="120" width="120"><br />PHP正则提取或更改图片img标记中的任意属性</center>';
//1、取整个图片代码
preg_match('/<s*imgs+[^>]*?srcs*=s*('|")(.*?)\1[^>]*?/?s*>/i',$str,$match);
echo $match[0];
//2、取width
preg_match('/<img.+(width="?d*"?).+>/i',$str,$match);
echo $match[1];
//3、取height
preg_match('/<img.+(height="?d*"?).+>/i',$str,$match);
echo $match[1];
//4、取src
preg_match('/<img.+src="?(.+.(jpg|gif|bmp|bnp|png))"?.+>/i',$str,$match);
echo $match[1];
/*PHP正则替换图片img标记中的任意属性*/
//1、将src="/uploads/images/20100516000.jpg"替换为src="/uploads/uc/images/20100516000.jpg")
print preg_replace('/(<img.+src="?.+)(images/)(.+.(jpg|gif|bmp|bnp|png)"?.+>)/i',"${1}uc/images/${3}",$str);
echo "<hr/>";
//2、将src="/uploads/images/20100516000.jpg"替换为src="/uploads/uc/images/20100516000.jpg",并省去宽和高
print preg_replace('/(<img).+(src="?.+)images/(.+.(jpg|gif|bmp|bnp|png)"?).+>/i',"${1} ${2}uc/images/${3}>",$str);
?>