Exception "Illegal characters in path" for some external images

DownloadImage method from WebImageAdaptorFilter does not escape illegal characters (\/:*?"<>|) from image's URL causing "Illegal characters in path" exception to be thrown. The illegal characters should be replaced with a dash ('-') or underscore('_').
Example:

<img src="image.php?id=23" alt="Image 1"/>
<img src="http://opi.yahoo.com/online?u=USERNAME&m=g&t=1" alt="Yahoo Macro" />

<img src="image.php-id=23" alt="Image 1"/>
<img src="http---opi.yahoo.com-online-u=USERNAME&m=g&t=1" alt="Yahoo Macro" />