let resources = window.performance.getEntriesByType("resource");
console.log(resource.name); // "http://example.com/some-image.webp"
console.log(resource.imageDecode); // 24.12001
Or, since this may be somewhat awkward to place into the resource timing API, what if it was its own API?
let images = window.performance.getEntriesByType("images");
console.log(image.name); // "http://example.com/some-image.webp"
console.log(image.time); // 24.12001
If this is already under consideration, then I apologize-- A cursory google search did not reveal anything like this for me, but my Google Fu can be lacking at times.
EDIT: Relevant tweet.