Hi, FWIW, Maperitive provides a "resolution" parameter to its generate-tiles command. The parameter is an integer value indicating the scale to use when rendering tiles - the default 1 renders 256x256 tiles. If you set it to 2, you get 512x512. Technically the whole thing is implemented by scaling the graphics, which is quite easy to do in GDI+ (.NET graphics engine). The user doesn't have to change the map style. I used the same technique to achieve the subpixel accuracy in Maperitive (since GDI+ doesn't provide for this): http://braincrunch.tumblr.com/post/13459650973/maperitive-beta-subpixel-accuracy
Best regards, Igor On Tue, Jun 26, 2012 at 11:05 PM, Frederik Ramm <[email protected]> wrote: > Hi, > > I have had some people asking whether I could supply them with "Retina" > map tiles. "Retina" is an Apple brand name for higher resolution displays, > and these users tend to mean tiles with twice the resolution. > > I wonder if anyone has done this already. I can think of a number of > possible angles to attack this: > > 1. Double all font sizes, line widths, etc. in the Mapnik style file > (recent Mapnik versions also have a built-in scaling option that achieves > about the same) and adapt all scale denominators accordingly. > > This would mean that meta tile size, tile size, and everything else would > remain unchanged but you'd be shifting everything by one zoom level - what > was on one z16 tile before is now on four z17 tiles. The "Retina" user > would see less detail on the same zoom level and therefore would have to go > down to z19 to see what is currently shown on 18. > > Also, font nastiness along the metatile edges would increase; the amount > of font nastiness depends on the ratio of tile size to font size, so > doubling font sizes and keeping metatile sizes will increase label clipping > and other strange things. (Simply increasing the buffer doesn't help.) > > 2. Modify style as per 1., but also double the size of meta tiles to > 4096x4096. Cut 16x16 normal tiles out of one meta tile, rather than 8x8. > This avoids the increase in font nastiness but requires internal processes > to adapt to larger metatiles. The "zoom level shift" problem is the same as > in 1. > > 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. > > Your thoughts on these options - are there more than these three, perhaps? > - would be most welcome. > > ("Tiles for printing" is a very similar issue - "print" users tend to want > quad-resolution tiles, and again you have the options of shifting the zoom > level by 2 or making 1024x1024 tiles.) > > Bye > Frederik > > -- > Frederik Ramm ## eMail [email protected] ## N49°00'09" E008°23'33" > > > ______________________________**_________________ > dev mailing list > [email protected] > http://lists.openstreetmap.**org/listinfo/dev<http://lists.openstreetmap.org/listinfo/dev> >
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