[OSM-dev] "Retina" tiles - best way to support them?

Peter Wendorff wendorff at uni-paderborn.de
Thu Jul 5 10:11:38 BST 2012

Am 05.07.2012 09:44, schrieb Frederik Ramm:
> Hi,
> On 06/27/2012 01:10 AM, Robert Joop wrote:
>>> 3. Modify style as per 1., double size of meta tiles to 4096x4096, and
>>> double size of tiles to 512x512. This avoids the increase in font
>>> nastiness *and* it has the nice effect that one "Retina" tile at a
>>> certain zoom level shows exactly the same content as a normal tile, 
>>> just
>>> on 512x512 instead of 256x256 and therefore at twice the resolution. It
>>> would, however, require clients (OpenLayers et al.) to work with the
>>> larger tile size.
>> This option sounded best to me as well.
>>> I just tried this out and found that, on a standard non-mobile
>>> Firefox browser, OpenLayers displays the new 512x512 tile just fine,
>>> it scales it to 256x256 in the browser. I can then use the browser's
>>> "zoom" function to blow up the OpenLayers display and while
>>> everything becomes jaggy when I do this with normal tiles, the map
>>> still looks nice when using the double resolution tiles. Does this
>>> mean that it would be an acceptable viewing experience for mobile
>>> users as well?
>> Most likely, I’d guess.
>> I’d like to try it on some devices with pixel ratio > 1, like the Nexus
>> One with its penTile display
>> http://en.wikipedia.org/wiki/Nexus_One#Hardware
>> or the iPhone 4.
>> Is your test setup publicly accessible?
> It is now, here:
> http://mull.geofabrik.de/hires.html
> By default this will come up with standard Mapnik tiles from osm.org, 
> but you can switch to my hires tiles in the layer switcher. If I do 
> this in Firefox on my desktop machine, there's hardly any difference 
> between the two, as OL downscales the images from 512x512 to 256x256 
> for display. Only if you right-click on an image will you see that it 
> is indeed bigger than normal.
You may simply zoom in in Firefox using Strg+"+" to see the benefit ;)


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