- From: Chris Lilley <chris@w3.org>
- Date: Mon, 20 Mar 2006 13:20:15 +0100
- To: Maciej Stachowiak <mjs@apple.com>
- Cc: Ola Andersson <Ola.Andersson@ikivo.com>, www-svg@w3.org, eseidel@apple.com
On Monday, March 20, 2006, 6:52:49 AM, Maciej wrote: MS> On Mar 17, 2006, at 6:35 AM, Ola Andersson wrote: MS> I think the SVG working group should reconsider this decision. The MS> current element names and content limitations do not effectively MS> express the needed semantics. The current definitions are that that MS> <image> is a "raster image format" and <animation> is an SVG Also that <image> is not a timed element, while <animation> is. As the spec says, Furthermore the 'animation' element supports timing and synchronisation attributes which allows multiple animations to run with independent timelines in the same svg document. Also that raster images do not contain content outside their bounding box - they are a rectangular array of pixels -and thus do not need clipping; while <animation> pointing to (potentialy) animated vector graphics can (and in Full, will have clipping). Note that the ability to stop and start parts of an animation is very desirable from a WAI standpoint; SVG 1.1 did not enable that because it had only a single timeline (which meets the WAI guidelines) ad we wanted to do better than that for 1.2. MS> Here are some use cases that are not very well covered by the current MS> definitions: MS> - An animated raster image format, such as animated GIF. Technically MS> this should be in <image>, but it seems confusing that the MS> animatability of SVG makes it disallowed for <animation> but that is MS> not the case for GIF. Its a well known flaw that animated GIF is served as image/gif. Leaving aside the fact that the GIF format itself forbids animation(!), a look at the IANA rules for the top level types shows that animated GIF should have been registered as video/gif (IANA video/* just means "sequence of images" not "full motion video".) Animated raster images are already covered, by the video element. MS> - A non-animated vector image format, such as PDF. Safari/WebKit MS> support PDF as an image format in HTML, and it seems like this should MS> not be disallowed for SVG. But since <image> only allows raster MS> formats and <animation> only allows SVG, Aha. <animation> should not only allow SVG. good catch. The conformance requirement should only require SVG, but other formats should not be disallowed there. MS> we would have to forbid this MS> to comply with the spec, and no SVG implementation could allow it MS> except via <foreignObject> which provides a much weaker degree of MS> integration than <image> or <animation>. Putting a PDF into foreignObject sounds fine to me, especially as its not animated and there is no need to independently control its timeline. MS> - An animated vector image format that is not SVG. Right now I don't MS> know of any SVG implementation supports such formats directly, but MS> suppose an implementation directly handled the Flash file format. It MS> could not be used as either an <image> or <animation>. See above. It should go on animation, if its to have its timeline controlled. Then again, as Flash is frame based .... MS> - A generic image viewer that would like to ignore the differences MS> between vector and non-vector images, and simply display an image MS> collection. For example, suppose I make a CGI script that finds a MS> random image on the web and redirects to it. Now I want to make an MS> SVG document that includes 40 such images, just by having 40 <image> MS> elements with appropriate size and placement. But, whoops, that won't MS> support SVG. In fact, there's no reasonable way to do this in a way MS> that makes SVG and other image formats interchangeable. Sometimes an MS> image is just an image! But now we can't treat something like <http:// MS> www.croczilla.com/~alex/old-site/tiger.xml> as an image. MS> On top of that this change is incompatible with SVG 1.1. Yes, it is. Unfortunately we had not closely read the SMIL spec and thus not realised that we should have used animation. However, another change from 1.1 to 1.2 is the addition of time containers; and there, it does not make sense to have them for static images. -- Chris Lilley mailto:chris@w3.org Chair, W3C SVG Working Group W3C Graphics Activity Lead Co-Chair, W3C Hypertext CG
Received on Monday, 20 March 2006 12:20:22 UTC