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Re: Adaptive images

From: Henri Sivonen <hsivonen@iki.fi>
Date: Tue, 31 May 2011 09:02:14 +0300
To: public-html@w3.org
Message-ID: <1306821734.2453.21.camel@shuttle>
On Mon, 2011-05-30 at 16:07 +0200, Simon Pieters wrote:
> 3. Use a single image that is supports progressive rendering and let the  
> UA abort the download when it has downloaded enough (like with <video>).  
> The UA can make a new HTTP Range request to download more (like with  
> <video>) of the image if the user zooms in. This might have compat issues  
> if done without opt-in, but we could introduce it as an opt-in feature  
> (e.g. new attribute that points to the big progressive image which lets  
> the author choose the fallback behavior).

This *might* work for interlaced PNGs. But is there a royalty-free image
format for photos that has the following properties:
 1) Compressing a photo has the same or better quality/size
characteristics as JPEG.
 2) To decode the image with both dimensions halved but with visually
the same quality as the full image, only the first quarter of data is
needed?

(E.g. JPEG 2000 tried to be that kind of image format but failed already
on technical grounds. IIRC, in practice to decode a JPEG 2000 image with
the dimensions halved, you need the first half--not quarter--of the data
to get proper quality.)

-- 
Henri Sivonen
hsivonen@iki.fi
http://hsivonen.iki.fi/
Received on Tuesday, 31 May 2011 06:02:44 UTC

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