[OSM-dev] Slippy Map, automatic Tile Rendering

Frederik Ramm frederik at remote.org
Sat Jan 20 02:21:10 GMT 2007


Hi,

> I'm wondering whether one of those "erode/dilate" filters you find in raster 
> graphics programs (e.g. imagemagick) would make the roads easier to see 
> against a white background, for low-zoom tiles?

I have played around with the Perl ImageMagick module and created a new 
version of lowzoom.pl (the script that generates level-11 to level-7 
tiles for the osmarender slippy map).

I used ImageMagick to apply the kind of "boldening" that I described in 
my last post. I found that the results looked best if levels 11 and 10 
are created as they are now, but for levels 9, 8, and 7 a correction is 
applied to keep the lines from becoming too faint.

If you're interested, look at these images (a bit larger than the last 
ones this time):

http://www.remote.org/frederik/tmp/tiles/comparison.html

I agree with those of you who said that the ideal way to generate *all* 
tiles is rendering them directly, and filtering out everything that 
should be omitted on a certain zoom level. We should keep this aim in 
mind for the long run, but what you see on the above web page could be 
in the slippy map within days if it finds favour.

So please take a look at it and give me some feedback. If there's no 
objection then I'd like to re-generate the slippy map tiles based on the 
"right column" method shown on the web page during the following week. 
There would be a period of approximately 24 hours where tiles of the new 
and old version co-exist which will look funny, but it'll go away quickly.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00.09' E008°23.33'




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