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Re: [css3-images] processing model for transformations (image() vs. image-orientation)

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Fri, 10 Feb 2012 17:33:24 -0800
Message-ID: <CAAWBYDDVg21xk1F+RbcgBqh7Rsfkk=E9XLFUH0e0W+_qO05oLw@mail.gmail.com>
To: "Kang-Hao (Kenny) Lu" <kennyluck@csail.mit.edu>
Cc: "L. David Baron" <dbaron@dbaron.org>, WWW Style <www-style@w3.org>, ML publc-i18n-bidi <public-i18n-bidi@w3.org>
On Wed, Feb 8, 2012 at 12:13 PM, Kang-Hao (Kenny) Lu
<kennyluck@csail.mit.edu> wrote:
> (Cc+ public-i18n-bidi)
>
> (11/12/01 8:22), Tab Atkins Jr. wrote:
>> On Wed, Nov 30, 2011 at 4:03 PM, L. David Baron <dbaron@dbaron.org> wrote:
>>> There are multiple features in css3-images that can transform an
>>> image.  For example:
>>>
>>> http://dev.w3.org/csswg/css3-images/#image-notation defines the
>>> 'ltr' and 'rtl' keywords which can cause an image to be flipped
>>> horizontally.
>>>
>>> http://dev.w3.org/csswg/css3-images/#image-orientation defines the
>>> image-orientation property which can cause an image to be rotated.
>>>
>>> It matters which one happens first, since doing them in a different
>>> order produces different results when image-orientation computes to
>>> 90deg or 270deg.  css3-images should define a processing model that
>>> says so.
>> [snip]
>>
>> Though, I guess they could potentially interact once 'content' can
>> define replaced elements.  In that case, I think 'image-orientation'
>> should apply *after* the contents have resolved to an image.  I'll add
>> some text to that effect.
>
> The spec now says
>
>  # If the image itself is transformed in some way (for example, if the
>  # content of an element is provided by the ‘image()’ function with a
>  # directionality opposite the element's directionality), the image's
>  # transformation must be applied before ‘image-orientation’ is. As
>  # well, ‘image-orientation’ must be applied before any further
>  # transformation of the element, such as through CSS Transforms.
>
> Is this actually right? I thought 'image-orientation' is meant to allow
> you to "correct" the image, say, from 「↑」 to「→」, so it should happen
> before anything else. If ltr/rtl reflection happens before 'image-
> orientation'(「↑」to 「↑」), you get only「→」instead of both 「→」and
> 「←」.
>
> Am I missing something?

Hm, that makes a lot of sense, particularly when we add an 'auto'
value for handling EXIF data.  Changed and recorded in the issue list.

~TJ
Received on Saturday, 11 February 2012 01:34:12 GMT

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