正则，如果img标签里没有alt，则加上alt= " "
<img src= "asdfas.gif " width= " " heigth= " " alt= "dsafa ">
-->
<img src= "asdfas.gif " width= " " heigth= " " alt= "dsafa ">
<img src= "asdfas.gif " width= " " heigth= " ">
-->
<img src= "asdfas.gif " width= " " heigth= " " alt= "dsafa ">
意思就是，有的话不管，没有则加上一个
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DC关注
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( <img(?![^\x3E]*?alt[^\x3E]*?> ).*?)>
可以吗？
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jf