Thanks for the info with regards to Guetzli, this is new to me and I'll be looking it up.
I use jpegoptim as well to optimize my jpegs.
I really have no idea what Shopify is doing with regards to image optimization these days, as once I moved over to imgix, I never moved back to cdn.shopify.com.
My post is nearly 2+ years old now, so things have changed most likely.
What about now, one year later ?
I think most good websites should have lazyloading for images, but even then product images have to be downloaded and shown on the first paint. I'm also looking for a way to optimize all my product images. Did Shopify improved on this ? Is this necessary to upload compressed product images or will Shopify do it for us now ? Finally, is there a way to compress all our product images with a script or something ? There are few apps on the store doing this, I figure we could replicate this with a script ?