[openstreetmap-website] Add retina support (#104)
frederik at remote.org
Fri Sep 21 15:59:19 BST 2012
Frederik here. (*)
On 09/21/12 16:40, Tom MacWright wrote:
> Adding support to OpenLayers shouldn't be too hard. Hosting costs
> are a different thing of course.
> No, it should and it will. This would necessitate serving 4x as many
> tiles (and thus as much bandwidth), redesigning the OSM style to work
> with a different scale factor (which would likely result in a duplicate
> set of icons, for which we only have bitmaps).
I have already done retina tiles a while ago with a standard,
Tirex-based tile server and Mapnik 2.1. Instead of serving more tiles, I
decided to double the size of a meta tile and then use the exact same
tiling schema for compatibility and less confusion - what is on tile
z/x/y.png in the standard rendering will also be on z/x/y.png in the
retina rendering. The advantage of this was that I had less rendering
artifacts around the meta tile borders than I would have had with
standard 2048x2048 meta tile size. OpenLayers "supports" this (for some
value of support) in that nothing breaks, but because OpenLayers
instructs the browser to scale the 512x512 tile to 256x256, the client
doesn't see a quality improvement. Other (iOS native) tiling
applications did however work great. I didn't bother redesigning the
style and simply instructed mapnik to render at scale factor 2 which,
thanks to Dane+Artem, now works really well and even scales bitmap
images in case you don't have access to scalable icons.
But I fully share TomH's notion that we're not about making a slick
application for users of high resolution displays out there. It would be
great to have a page on switch2osm.org that explains how you can
effortlessly make retina tiles but we don't have to make them ourselves.
(*) This in response to
Frederik Ramm ## eMail frederik at remote.org ## N49°00'09" E008°23'33"
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