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Re: what statistical data supports gif and jpeg to be the chosen image formats?

From: Francois Daoust <fd@w3.org>
Date: Tue, 16 Dec 2008 10:51:33 +0100
Message-ID: <49477A25.4000008@w3.org>
To: Johannes Hertz <johannes.hertz@gmail.com>
CC: public-mobileok-checker@w3.org

Hi Johannes,

To make sure we're talking about the same thing, let me quickly 
introduce the context. Most of the tests defined in mobileOK are 
evaluated against an hypothetical mobile device with pretty minimal 
capabilities. We call it the Default Delivery Context (DDC), and it is 
indeed defined as the "minimum delivery context specification necessary 
for a reasonable experience of the Web":
  http://www.w3.org/TR/mobile-bp/#ddc

The DDC has other limitations that you may or may not find accurate 
depending on the usual pool of devices and networks you're used to 
targeting. For instance, the total size of the page must not exceed 20 
kilobytes, images and style sheets included.

The message carried out by mobileOK is not "develop for the DDC, 
period", but rather "when unaware of the capabilities of a device, 
suppose that it matches the capabilities of the DDC". Content adaptation 
is encouraged. If you can identify the user's device and improve the 
user experience consequently, go ahead! Content adaptation does not 
prevent your Web site from being mobileOK (the checker sends very 
specific HTTP headers to retrieve the resources).

That said, why no support for PNG in the DDC?

The DDC was defined a couple of years ago. At the time, stats showed 
that there was good support in western countries, but limited PNG 
support on Japanese mobile devices, whereas GIF and JPEG were broadly 
supported throughout the world.

I am not sure about the situation in Japan today, but you are probably 
right: most of the devices now support PNG (PNG transparency is not as 
widely supported, but that's another matter). The definition of the DDC 
is expected to be stable though still to evolve slowly over time (where 
slowly means, say, every few years, when oldest mobile devices disappear 
from the market, and the baseline starts to change). Support for PNG is 
a very good candidate for a potential updated version of the DDC!

Francois,
W3C Staff Contact,
Mobile Web Best Practices Working Group.


Johannes Hertz wrote:
> What is the statistical data behind decision to recommend GIF and JPEG 
> to be the only allowed formats in Mobile OK sites? For me (being a 
> mobile developer since 1996) it doesn't seem to be based on any factual 
> statistics. How old browsers are you referring to? I am under the 
> impression that majority of the mobile browsers support at least PNG-8. 
> Also for example J2ME MIDP2.0 specs say that PNG is always supported and 
> JPEG + GIF optionally so it is kinda ridiculous to support PNG in Java 
> and leave it out in the browser.
> 
> Yours,
> J. Hertz
Received on Tuesday, 16 December 2008 09:52:08 GMT

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