Losslessly compress image as much as Google's PageSpeed Insights

Question

I'm optimizing my webpage using Google's PageSpeed Insights. It recommends:

Losslessly compressing http://mysite.com/.../image.jpg?... could save 33.6KiB (23% reduction).

However, when I upload this image to Yahoo! Smush.it it's only able to compress it by 8KB, not 33 KB.

What kind of super compresser is Google using? How do I do that?

Answer 1

There is this link which provides some generic information regarding compression optimisations for images : https://developers.google.com/speed/docs/best-practices/payload?hl=fr#CompressImages

But it's also interesting to note that Google has tried (without success so far) to promote its own image compression format, under the name of WebP, which is supposed to provide better compression ratio. https://developers.google.com/speed/webp/