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I just used it on a largish JPG. The JPG went from 289K to 119K, but kept the same resolution (very large!) and does indeed look the same. Magic!
Tip
Use the "shrinking" service at the end of the work-flow to maximize the amount of shrinking possible. That is, do it after you have the final cropped, at the desired resolution.
Inverting colors
http://www.converthub.com/invert-colors/
Used to convert white-on-black logo from the Physics web site to a black-on-white logo for use with our calling cards. Neat!
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Still "to do"
Chemistry still has that big job of "image management" and curation which still needs to "sit" somewhere (and it is much larger and broader than the "Chemistry web site", per se). Anyway, whoever will be doing this will have a much easier job now that we've identified these tools.