[whatwg] <img> element comments

Henri Sivonen hsivonen at iki.fi
Sat Nov 4 03:49:37 PST 2006

On Nov 4, 2006, at 08:37, Ian Hickson wrote:

> I'm thinking of only allowing integer values, and requiring them to be
> equal to the dimensions of the image, if present (and requiring  
> both to
> be present if either is present). Would people be ok with that?

What about non-square pixels in the image file? Both GIF and PNG  
allow pixel aspect ratios other than 1:1. I don't have test cases and  
I don't know what browsers do.

Also, such a requirement would make document conformance dependent on  
resources other than the (X)HTML5 file itself. Is that a good idea?  
Is the document conforming, not conforming or undecided if there are  
no other errors but the image cannot be retrieved? What image formats  
should a conformance checker know about? GIF, PNG and JFIF?

Sniffing the pixel dimensions (without the aspect ratio) out of GIF  
or PNG is both easy and efficient if the conformance checker can  
assume that image files are conforming and don't need to be fully  
decoded. JFIF looks harder.

>> * Perhaps we can allow content for XML documents?
> That's tempting. We'd have to allow it for HTML too (via DOM
> manipulation). I'm not sure, though. <object> is pretty buggy,  
> wouldn't
> this just cause <img> to get those bugs?

Also, it would cause further divergence between the serializations...

Henri Sivonen
hsivonen at iki.fi

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