Google Pagespeed for Nginx and Apache is another way to go. The benefit of this approach is that you don't have to bulk out your code.

As for metadata, today I decided to add it back in.

https://www.gs1.org/sites/default/files/docs/gdsn/Product_Im...

For ecommerce it will eventally help to have product data, e.g. brand, product name etc embedded in the image.

My other tip if you go the Imagemagick/PAGESPEED route then you can use 4:2:2 colour space and ditch half the bits used for chroma.