A few years ago, MaxCDN published a post on Better Image SEO with Canonical Headers in which they suggest specifying a canonical link in the HTTP header. Google's documentation on this, however, states "Google currently supports these link header elements for Web Search only." This seems to imply that it would not benefit image searches. It seems that it would be a good idea -- and the kind of thing Google would do, so I am wondering if there is a benefit to setting a canonical link for duplicate image content. Has anyone done a test of this?
Just to provide a little more specifics for my scenario, I am using a CMS that utilizes ImageProcessor.Web which can resize images and for JPEGs, reduce the size (by reducing the quality). I think it would be useful if the site served smaller, reduced quality images but had the canonical link set to the original.