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I'm working on a mobile website and on some devices (in my particular test, an iPhone 4) when visiting the site over 3G the images are compressed and look unacceptably fuzzy. When visiting the site over wifi (and clearing cache AND quitting Safari) the images appear as expected.

We've reduced the image size as much as possible without losing quality (between 2 and 26KB) and added the 'no-cache' fix recommended on another post:

<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="pragma" content="no-cache">

Still no luck!

Is there anything else we can do to force the image quality over 3G?

Thanks, Kev

Community
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Kevin
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  • Does the image type matter? We're currently using jpgs for these images (1 logo, 1 button, 1 photo). – Kevin Apr 19 '11 at 09:24
  • Well, if you switch to png, then chances are that the images will be left verbatim. The reason is that resizing is complicated (because of layout), and png is lossless, therefor the quality cannot be reduced. – Roman Apr 19 '11 at 09:44
  • Thanks Roman - switching to PNG worked a treat. Thanks for the help. – Kevin Apr 19 '11 at 10:30

3 Answers3

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It's the mobile carrier's proxy that modifies images.

Roman
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The HTTP header cache-control: no-transform is what you are looking for see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9.5 for full details.

It's not clear if all proxies respect it though.

Andy Davies
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Yep, easy to fix. Download Proxomitron and install as explained on their site. Be sure to add a shortcut to it in your Programs -> Startup folder so it runs when Windows boots.

In Proxomitron's Headers section (just click the button in the small window) add a new filter. Set the 'HTTP Header' to 'Cache-Control (out)', then set the 'Replacement text' to 'no-cache'. Ok it, then check the box next to it in the list under Out.

Proxomitron does a lot of cool stuff, and this simple fix makes Chrome work as expected without image compression via mobile 'broadband'.

CableGuy
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