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

Frederik Ramm frederik at remote.org
Thu Jul 5 08:44:25 BST 2012


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:


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.

I'd be interested in hearing from users of high-resolution displays if 
these big tiles actually make a difference (except being slower to 

Feel free to play with these tiles (tile URL is e.g. 
http://mull.geofabrik.de/osm2x/6/33/21.png), but note that this is a 
play server that may or may not be working, and is likely to be slow 
(currently pre-rendered only up to z11), and also I'll probably drop 
this tile set in a few weeks so if you read this in a mailing list 
archive later the link will be dead.


Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"

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