[mapserver-users] Label text always clipped by tiles

Jean-François Gigand jean-francois at gigand.fr
Wed Jan 26 11:00:07 EST 2011


Hi,

I met the edge issue when I had to produce statistics maps with
proportional symbols.

TileCache addressed the issue indeed, with the "metaBuffer" option
(see http://tilecache.org/docs/README.html#configuration).
It means that MapServer will be called to generate larger tiles which
are then cropped by TileCache, which has a time processing cost.

The "metaTile" is meant to optimize this by rendering multiple tiles
as a single one.

Jeff

2011/1/26 Gregor at HostGIS <gregor at hostgis.com>:
>> I was using TileCache, but I switched it off to debug this problem. If
>> TileCache generates larger tiles, will there still be clipped labels?
>> Just fewer clipped labels? I don't think this is a workable solution
>> for me, but if I have the time I'll try it.
>
> Correct; there would be FEWER labels clipped (if you force them and allow
> partials) or missing (if you disallow partials).
>
> How many fewer, depends on how large you make your meta-tiles. If they're
> 5x5, that's a significant reduction in the number of tile edges. If you
> really turn up your MAXSIZE in your mapfile, you could potentially make
> 10x10 meta-tiles; that's 1% as many tile edges.
>
> You could also make your tiles larger. If you have 512x512 tiles, and 10x10
> meta-tiles, that's a HUGE reduction in the number of tile edges over single
> 256x256 tiles.
>
> The only method I know that would eliminate ALL tile-edge artifacts, would
> be to eliminate tiling, e.g. singleTile:true in OpenLayers. Not that that's
> a great solution either, but it is sometimes the only way.
>
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