<div>Hi,</div><div><br></div>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.<div>
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.</div><div>I used the same technique to achieve the subpixel accuracy in Maperitive (since GDI+ doesn't provide for this): <a href="http://braincrunch.tumblr.com/post/13459650973/maperitive-beta-subpixel-accuracy">http://braincrunch.tumblr.com/post/13459650973/maperitive-beta-subpixel-accuracy</a></div>
<div><br></div><div>Best regards,</div><div>Igor<br><br><div class="gmail_quote">On Tue, Jun 26, 2012 at 11:05 PM, Frederik Ramm <span dir="ltr"><<a href="mailto:frederik@remote.org" target="_blank">frederik@remote.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
<br>
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.<br>
<br>
I wonder if anyone has done this already. I can think of a number of possible angles to attack this:<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.)<br>
<br>
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.<br>
<br>
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.<br>
<br>
Your thoughts on these options - are there more than these three, perhaps? - would be most welcome.<br>
<br>
("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.)<br>
<br>
Bye<span class="HOEnZb"><font color="#888888"><br>
Frederik<br>
<br>
-- <br>
Frederik Ramm ## eMail <a href="mailto:frederik@remote.org" target="_blank">frederik@remote.org</a> ## N49°00'09" E008°23'33"<br>
<br>
<br>
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