RE: Feedback on Image modules

> From: www-style-request@w3.org [mailto:www-style-request@w3.org] On
> Behalf Of Brad Kemper
> Sent: Friday, December 17, 2010 5:00 PM
> To: Charles Pritchard
> Cc: Anthony Ricaud; Anne van Kesteren; Tab Atkins Jr.; www-style list
> Subject: Re: Feedback on Image modules
> 
> On Dec 17, 2010, at 3:29 PM, Charles Pritchard <chuck@jumis.com> wrote:
> 
> > Mainly, we use it when a resource can't be found/connected to: but
> I'm sure we'll also
> > be adding in logic for conditional support of the new WebP format.
> >
> > As most of us know, "guessing" on an image format based on the
> extension is not workable--
> > until/unless the extension has already been fetched, or peeked at via
> HEAD, for a mime content type.
> 
> Is isn't good for selecting formats you do support, but isn't it still
> helpful for eliminating those you don't support? For instance, you
> could peek further for '.php', but not bother to do so for '.psd' if
> you know you won't support Photoshop files.

Then let the author give explicit unambiguous format hints, as done in 
CSS3 Fonts. I agree that depending on file extensions is a bad idea; at
a minimum, doing so without defining all those file extensions and what 
formats they map to makes it harder to create solid testcases.