SSImageMin::set_cached_filename
This function creates the filename of the new image using an MD5 hash of the original filename. This helps to create a unique filename for the newly compressed image so that this class can easily find and determine if the image has already been compressed and stored locally.
Employing use of the "alt" and "title" tags on the image (which hopefully you're already doing) will negate any potentially negative impacts on SEO. See this article for more information: http://searchenginewatch.com/article/2120682/Image-Optimization-How-to-Rank-on-Image-Search
Signature
protected function set_cached_filename()