I have been using ewww for years. While running a Google PageSpeed Insights test for a client’s site, I noticed several images aren’t up to the mark. EWWW said it’s compressed. So, downloaded the optimized files from Google PSI and compared with the original images.
ImageMagick has a nice command line utility called identify that helps to find the “Q”uality of the image compression. To find it out, use the following command…
identify -format '%Q' imagename.jpg
Make sure your server has imagemagick. lol.
It looks like Google uses lossy compression with 85% of the original image quality. So, a loss of 15%.
Later, I noticed that it is a common query in recent times in the official PSI forums too. I am glad I am not alone. 🙂