[whatwg] Add "naturalOrientation" property to <img>

Tab Atkins Jr. jackalmage at gmail.com
Fri Aug 26 14:45:22 PDT 2011

On Fri, Aug 26, 2011 at 11:10 AM, Mark Callow <callow_mark at hicorp.co.jp> wrote:
> On 11/08/26 10:03, Tab Atkins Jr. wrote:
>> On Fri, Aug 26, 2011 at 9:57 AM, Glenn Maynard <glenn at zewt.org> wrote:
>>> Rather than baking magic EXIF constants into the API, would it make more
>>> sense to translate to degrees?
>> Possibly.  However, 4 of the EXIF orientations (2, 4, 5, and 7) are
>> "unnatural" orientations that require mirroring the data as well as
>> rotating it.
>> We'd also need to decide whether the reported rotation is how much it
>> differs from upright or the rotation needed to return it to upright
>> (the difference between 90deg and -90deg).
> The EXIF constants do not represent a degree of rotation. They describe
> how the rows and columns of the image data map to the top and bottom of
> the image so more flexible in some ways, as evidenced by the possible
> "unnatural" orientations, and less flexible in others.

I'll avoid arguing nomenclature; we're describing the same thing.

> When EXIF orientation is present in the JFIF/EXIF file, I would hope the
> browser would apply it whenever decoding the file and creating the image
> object. If it does so , there should remain relatively few cases where
> the webapp needs to read the image's natural orientation. But I have no
> objection to such a property being added.

Browsers ignore the EXIF Orientation tag, and by now I suspect that's
needed for web-compat.  You can test your browser by visiting
<http://www.xanthir.com/etc/exif/> if you'd like.


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