[karim79]

Try out the https://kraken.io plugin. Kraken.io's optimization is more about fidelity to the original than maximising file size savings.

[stevesearer]

Can vouch for Kraken.io -- I've just begun using it to optimize ~50k+ interior architectural images so fidelity is important to me and my users. I'm about a third of the way done with the project and am saving just about 40% in size on average.