> On May 29, 2015, at 2:11 PM, Yoav Weiss <y...@yoav.ws> wrote: > > On Fri, May 29, 2015 at 8:34 PM, Sam Weinig <wei...@apple.com > <mailto:wei...@apple.com>> wrote: > Hi Yoav, > > Can you give a concrete example of when this will be used? I’m having > trouble understanding when an author will want to change an images intrinsic > size but not have control of the markup. > > It's not about control over markup, it's about control over style. > > Let's say you're now given the following task: write a script that will go > over all your server's HTML files and make your images responsive by adding a > `srcset` attribute to all <img> tags. Since some of the images may change > their display dimensions at different viewport sizes (i.e the "variable > width" use case > <https://dev.opera.com/articles/native-responsive-images/#variable-width-images>), > you want to add multiple resources with `w` descriptors to each <img>. Each > one of these resources will be pointed towards your shiny new image server, > which has access to the original high-quality image as well as the currently > displayed one (the "src image"). > > But, since you don't know if all the images have their dimensions defined in > CSS (and you suspect that a large chunk of them don't have CSS based > dimensions), you want to make sure that the intrinsic dimensions of the > displayed images remain the same even when you deliver images of varying > "physical" dimensions. How can you achieve that? > > Well, the answer is, you want to modify the intrinsic size of the delivered > images to be the same as the "src image"'s intrinsic dimensions. With > Content-DPR, that's easy. You simply set it to the value that is the > delivered image width divided by the "src image" width. > That way, the browser takes the Content-DPR into account, scales the > delivered image and it ends up with the same intrinsic dimensions as the "src > image". >
Hi Yoav, Sorry, but I’m afraid I’m still not really getting it. Can you get even more concrete? Perhaps provide some a sample page that would need this kind of functionality and go through what Content-DPR values would be used? - Sam > If you don't have markup control, the same exercise applies, but would > require the full-fledged Client-Hints in order to actually deliver resized > images. > > >> On May 29, 2015, at 11:23 AM, Yoav Weiss <y...@yoav.ws >> <mailto:y...@yoav.ws>> wrote: >> >> As a first step towards the Client-Hints implementation, I submitted a patch >> <https://bugs.webkit.org/show_bug.cgi?id=145380> for Content-DPR support >> <http://igrigorik.github.io/http-client-hints/#confirming-selected-dpr>. >> A discussion followed on the thread, so I'd like to move it to the list, in >> order for it to get higher exposure. >> >> Content-DPR is an HTTP response header that enables style-agnostic image >> resizing, > > What exactly does "style-agnostic image resizing” mean? I am not familiar > with that term > > It's not an official term. I meant to say that it enables you to perform > image resizing without taking into account the style rules that control the > way in which the resized image will be displayed. > > >> by enabling the server to adapt the image's intrinsic size so that layout >> will not break, even if the image's dimensions are not defined in style. >> >> Opinions welcome! :) >> _______________________________________________ >> webkit-dev mailing list >> webkit-dev@lists.webkit.org <mailto:webkit-dev@lists.webkit.org> >> https://lists.webkit.org/mailman/listinfo/webkit-dev >> <https://lists.webkit.org/mailman/listinfo/webkit-dev> > >
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