Improvement request: document how to reduce images by 90%

[michaeleiselsc]

As part of getting people to leverage WebP for their app, it would be great to see how to get the 90% reduction that is discussed in http://engineering.dollarshaveclub.com/shaving-our-image-size/. I tried an images with the -lossless flag, and I didn't get that 90% reduction, so then I tried lossy with -q 90 and got an even larger image! Here's the image I used:

Perhaps I'm not using the correct flags? Or perhaps the dollar shave club wasn't compressing pngs as far as they could? Any suggestions would be greatly appreciated, thanks!

[michaeleiselsc]

(of course, for that specific image, we could also be using a UIView with some clipping strategy)

[daltoniam]

Your file size reduction percentage is going to vary based on the PNG being used. You aren't always going to get 90% difference especially when the PNG is already a small file size (normally single color, simple design, etc). We saw a 90% size reduction because we have very detailed and large images.

Also there are some case studies that can be found here:

• https://developers.google.com/speed/webp/docs/webp_lossless_alpha_study
• https://developers.google.com/speed/webp/docs/webp_study