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Re: [webkit-dev] Accept- & Content-Resolution headers proposal

From: Peter Speck <speck@vitality.dk>
Date: Thu, 07 Jun 2007 17:48:20 +0000
Message-Id: <CDC2D7FA-1617-43A3-9E1D-6FD77B320A67@vitality.dk>
Cc: ietf-http-wg@w3.org, Web-Kit Dev <webkit-dev@opendarwin.org>
To: Nicholas Shanks <contact@nickshanks.com>




On 07/06/2007, at 19:18, Nicholas Shanks wrote:

>> Why force a "next size up" if most UAs prefer a dpi which is  
>> "close enough"?
>
> Do they? I guess it depends. I don't mind spending the bandwidth  
> for better looking graphics, but someone on a pay-as-you-download  
> phone most likely would.

But the UA should be able to tell this in the header, so normal  
browsers have more leeway in scaling up, but phones can prefer low- 
resultion.

>> All the other Accept-XXX headers (except Accept-Ranges) uses a  
>> wildcard if other values are accepted, e.g. (RFC 2616)
>>   section 14.2:  Accept-Charset: iso-8859-5, *
>>   section 14.3:  Accept-Encoding: gzip, *
>>   section 14.4:  Accept-Language: da, en, *
>>
>> All 3 supports adding a "quality value which represents the user's  
>> preference for that charset/...".  Could this be used to allow the  
>> UA to tell the server if it wants a "higher up" or "closest"?
>
> something like "Accept-Resolution: 200; allow-closest" to allow  
> 180dpi images to be sent, and "Accept-Resolution: 200" to get the  
> 240dpi images? I can't see a way to shoe-horn q= parameters into  
> doing this in any meaningful way.

If we leave out the "dpi" tag and allow the value to be a range, it  
could be specified as:
	Accept-Resolution: 70-80;q=3, 50-150;q=2, 150-400;q=1

(note that comma separates the items in an accept header, not  
semicolon.)

A high-resolution for printing would use e.g.:
	Accept-Resolution: 300-400;q=3, 200-600;q=2, 50-2000;q=1

> An asterisk would be implied because there will always be a closest  
> match, even if the only resolution is lower than a client  
> requested. (i.e. There would be no 406 errors because of this header)

If we allow a range, why not? Then the UA would be able to say: "I  
dont want any media for dpi > 100". Cell phones could use this to  
avoid download of huge files.

>> I assume this would be used too when printing a web-page, so the  
>> printed output can use high-resultion images.  (I've implemented a  
>> page which uses high-resolution GIFs for icons, and it is a pita  
>> to maintain).
>
> I'd be interested in seeing that, just for curiosity's sake.

A summer rental house:
http://www.dancenter.co.uk/house/11508/20071110

If you click on the "Print page" you get a page using higher- 
resolution media:

1) The red icons to the right on the page, e.g. "grocer's shop", are  
sent as 150 dpi versions. I fould that 150 dpi was sufficient for  
pretty output, and 300 dpi was not needed.

2) Photos are sent in a slightly larger version.


(the page lack a lot of text (and might have really bad English) as  
the site is provided primarly in German and Scandinavian due to the  
market).

----
    - Peter Speck
Received on Thursday, 7 June 2007 18:06:58 GMT

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