[MapProxy] Reprojecting WebMercator

[André Pirard]

On 2014-08-14 11:08, Oliver Tonnhofer wrote :
> Hi,
>
> On 12.08.2014, at 17:08, julien.kazemifard at visioterra.fr wrote:
>> Does someone have an idea on how to do such reprojection without this problem ?
>> I noticed this happens for every reprojection I try to do from EPSG:3857 to EPSG:4326,  for example OSM and Bing,
>> But only for the first levels...
> Its an artifact of the image reprojection. MapProxy does not reproject each pixel, this would take seconds, but it reprojects smaller grids of the image. The more grids you reproject, the better but also slower are the results. The current number of grids works great for most reprojections. You'll see issues like you got only on small scale maps with reprojections that result in large distortions of the image.
It might be an idea to (optionally?) use finer reprojection from source
to cache (that is, potentially building for several requests) and
coarser one from cache to service.  That way, avoiding the artifacts
would only be a matter of building the cache with the same projection as
the typical requests).

André.




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