[MapProxy] mixed cache format from png source

[Pestereva, Anna]

Hello all,

We are trying to achieve optimal tile size for WMTS streaming based on a
all-PNG TMS source. For that we turned to mixed cache format, however it
seems the size of each .mixed tile in cache is still 150-180kb, and
IrfanView reads them as PNG type - although they are not at the edge of the
dataset, so should technically become JPEGs and be 20-30kb..

We also have other TMS sources that are stored in JPEG+PNG format, and when
mixed cache format is applied to that source - we can definitely take
advantage of the underlying JPEG tile sources and decrease the size of
streamed WMTS tiles. IrfanView also reads those streamed tiles as JPEG type
as expected. All good in this case.

By the way, before we enabled mixed cache format for the mixed tile source
- cache tiles were streamed as PNGs and of PNG level size (150-200kb). So
it seems, MapProxy did convert our JPEG source tiles into PNG cache tiles.
Now, coming back to the first paragraph, my question is - would it convert
my source PNG tiles into JPEG-type cache tiles of mixed format? Or would we
ultimately need to re-tile our data into JPEG+PNG TMS source to be able to
actually take advantage of smaller tile sizes of mixed cache format for
streaming?

I wonder if I am doing something wrong or this is how MapProxy works?

Here is a sample of our cache config (first one produces needed results,
second one not):


  MixedSource_cache:

    grids: [webmercator]

    sources: [MixedSource_p_tms, MixedSource_j_tms]

    format: mixed

    request_format: image/png

  PNGSource_cache:

    grids: [webmercator]

    sources: [PNGSource_p_tms]

    format: mixed

    request_format: image/png

Thanks in advance!

-- 
*Anna Pestereva, GISP | Application Developer & Cartographer*
*Aerial Services, Inc. (ASI) *
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APestereva at AerialServicesInc.com <apestereva at AerialServicesInc.com> |
LinkedIn <http://www.linkedin.com/in/annapestereva>
*www.AerialServicesInc.com* <http://www.aerialservicesinc.com/> |
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