[whatwg] Canonical Image and Color

Brian Blakely anewpage.media at gmail.com
Mon Feb 11 16:17:25 PST 2013

Sure thing.  Let me go through the use cases that I see as applicable
today, derived from instances where an existing vendor or service currently
utilizes a non-standard implementation.

* Social network sharing

Facebook currently scrapes "OpenGraph tags" from shared pages to create a
content snippet.  One such tag is og:image, which specifies the image to
display in that snippet.  Twitter and Google+ use these same tags in
addition to their own implementations for developers.  For the title and
description of the snippet, scrapers will fall back to <title> and the meta
description.  A canonical image would serve the same purpose, but for
visual content.

* News aggregation

Flipboard, a highly visual, magazine-style news and article reader,
displays a hero image from the target page.  It does this by parsing and
analyzing the <img> elements in a page, sometimes displaying a non-optimal
or even vacant result.  A canonical image would allow developers to control
this kind of representation with more specificity, and provide the 3rd
party app with another presentation option.

* OS Integration

Apple currently parses their own "apple-touch-icon" element that specifies
which image will serve as a web application's icon after the user has added
to the homescreen.  Android's browser uses this same element, while
Microsoft uses a similar "msapplication-TileImage".  When these element is
not specified, a screenshot of the website is used instead or, in
Microsoft's case, the favicon.  Firefox OS has still another means of
implementation for this.  A canonical image could either replace or provide
an additional fallback for this functionality.

* Color

In all these cases, a canonical color allows external parsers to provide
further branding or additional flourish in their representation of apps and
pages.  Microsoft's "msapplication-TileColor" and
"msapplication-navbutton-color" elements aim to fulfill this purpose in IE
by coloring the app's tile on the Windows 8 homescreen and IE's own
navigation UI, respectively.

On Mon, Feb 11, 2013 at 5:41 PM, Tab Atkins Jr. <jackalmage at gmail.com>wrote:

> On Mon, Feb 11, 2013 at 2:33 PM, Brian Blakely <anewpage.media at gmail.com>
> wrote:
> > * Proposal
> >
> > Meta elements for defining a canonical image and color to be associated
> > with the page(s) in which they are included.  This is intended for use by
> > user agents and third-party applications (such as social networks),
> > referred to collectively as "parsers" in this document.  It is inspired
> by
> > Microsoft's recent work in site pinning and Apple's "standalone" webapp
> > implementation in iOS Safari.
> Can you elaborate?  I have no idea what UAs and third-party apps would
> do with a "canonical image" or "canonical color".
> ~TJ

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