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Re: [css3-images] How does image-orientation interact with EXIF data?

From: Simon Fraser <smfr@me.com>
Date: Wed, 15 Feb 2012 16:34:58 -0800
Cc: "www-style@w3.org list" <www-style@w3.org>
Message-id: <37951C7C-C701-4F04-AD82-E7CBBCB6F8A8@me.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
On Feb 15, 2012, at 4:24 PM, Tab Atkins Jr. wrote:

> On Tue, Feb 7, 2012 at 12:24 AM, Simon Fraser <smfr@me.com> wrote:
>> CSS3 Images talks about images being encoded sideways, and how this can be corrected for presentation via the image-orientation property:
>> <http://dev.w3.org/csswg/css3-images/#image-orientation>
>> 
>> However, it doesn't describe how this interacts with EXIF data in the image. My understanding is that an image may be tagged with EXIF data that indicates that the camera was in landscape orientation when the picture was taken, but this does not affect how the image is encoded.
>> 
>> I think the spec needs to talk about how image-orientation and EXIF rotation data interact.
> 
> There's a note in the spec now about the fact that browsers ignore
> EXIF data.  I plan to add the ability to auto-rotate based on exif
> data to level 4.  Is this sufficient to address your comment?

I still don't think it's really clear. The spec says:

> Sometimes images from camera phones, digital cameras or scanners are encoded sideways

and then in the Note:
> Note that in CSS, orientation data encoded in the image (e.g. EXIF data) is ignored

The difference between "encoded sideways"  and "orientation data encoded in the image" seems too subtle. Maybe the note should refer to metadata or even EXIF explicitly.

I don't know the history of image-orientation (the earliest reference on the list is http://lists.w3.org/Archives/Public/www-style/2004Jan/0249.html in 2004), but I still think that orientation issues related to EXIF are way more frequent than those due to encoding sideways. I question whether this property will be used often enough to warrant its inclusion.

Simon
Received on Thursday, 16 February 2012 00:35:39 GMT

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