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[css3-transitions] Interpolating images

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 30 Nov 2010 12:44:40 -0800
Message-ID: <AANLkTikicdiEW1HQTMe7XbaXHF9Zz1jkeUS=MAR7juAA@mail.gmail.com>
To: www-style list <www-style@w3.org>
Currently, images in general can't be transitioned.  It's been
suggested before that we allow such transitions, implementing them as
a cross-fade between the two images.  Would it be acceptable for me to
specify this behavior in Image Values, or is it something we'd rather
put off until Transitions 4?  Either decision is acceptable to me; I
just want to put a note into Image Values if we decide on the latter.

There is an obvious issue with transitioning between images of
different sizes, with a few different solutions:

1) In addition to crossfading, scale the images between the starting
and ending size, so they always match in size.  This is probably
expensive.  As a benefit, it's clear what the size of the cross-faded
image is, for the purpose of background-repeat, background-size, etc.

2) Treat it as transitioning between two infinite layers.  Sections
outside of each image would just be transparent pixels.  You'd then
just do a naive pixel-based cross-fade.  This doesn't give us a clear
answer about the image's size, though.

I don't know if there are any further issues or not here.

So, should I add a note to Image Values saying "general <image>
interpolation will be specified in a later version of Transitions", or
should I try and define it here?

~TJ
Received on Tuesday, 30 November 2010 20:45:33 GMT

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