[OSGeo Oceania] Geowebcache tile naming scheme

[adam steer]

Hey Alex,

I found that - but there’s nothing on ‘what is x’ and ‘what is y’. For
example if I start y and y at bottom left (of a +-180 degree lon, +-90 lat
grid), the x and y given in the tile names is noplace near where that tile
exists in lat and lon (the grid schema says top left == false, so bottom
left should be x=0, y=0 in the grid, right?)

I have my reasons for needing to unpack this stuff :D

Cheers

On Wed, 24 Apr 2019 at 10:24, Alex Leith <alexgleith at gmail.com> wrote:

> Hey Adam
>
> Here's a discussion on the file naming for GWC:
> https://sourceforge.net/p/geowebcache/mailman/geowebcache-users/thread/28819540.post%40talk.nabble.com/#msg25474083
>
> Looks like the plan was `
> layername/projection_z/[x/(2^(z/2))]_[y/(2^(z/2))]/x_y.extension`
>
> But then it changed along the lines of: "the bit shifting starts with 2,
> effectively making it `2^( 1 + ( z / 2 ))` And there's some zero-padding."
>
> Personally, I think re-implementing the cache creation process in Python
> will be rather tedious and there will be a lot of mess between generating
> the data and having it 'just work' in GeoServer.
>
> I'll ping you on Slack ;-)
>
> Cheers,
>
>
>
>
> On Wed, 24 Apr 2019 at 10:08, adam steer <adam.d.steer at gmail.com> wrote:
>
>> Hi Oceanians
>>
>> is anyone out there extremely familiar with geowebcache’s tile naming
>> schemes - for example given a grid schema what are the decisions behind how
>> map tiles are named?
>>
>> Essentially given a grid schema declaration and a bunch of imagery I need
>> to replicate what GWC does in Python. …and unfortunately gdal2tiles / the
>> OSM tile naming code doesn't use the same tile naming / indexing schema (it
>> needs to match exactly an existing tiling schema - which is custom, and I
>> haven’t managed to decrypt yet).
>>
>> What I’m missing is a likely small but very critical piece of logic which
>> will let me map from geographic bounds to tile index locations, for example
>> from:
>>
>> input_tiff(minx miny maxx maxy) -> /zoomlevel/????/????_????.png
>>
>> …for output tiles in EPSG4326 (plate carree), indexed to lower left
>> corner.
>>
>> I’ve been digging into Geowebcache code, but Java does my head in and the
>> wormholes get too deep in there. I can’t find any documentation which
>> really explains well how this mapping is done.
>>
>> I have a small budget for an hour of your time; alternately feel free to
>> respond in public and I will buy you beer/dinner/give good mojo to FOSS4G
>> SotM Oceania.
>>
>> Thanks!
>>
>> Adam
>>
>> --
>> Dr. Adam Steer
>> http://spatialised.net
>> https://www.researchgate.net/profile/Adam_Steer
>> http://au.linkedin.com/in/adamsteer
>> http://orcid.org/0000-0003-0046-7236
>> +61 427 091 712 ::  @adamdsteer
>>
>> Suits are bad for business: http://www.spatialised.net/business-penguins/
>> _______________________________________________
>> Oceania mailing list
>> Oceania at lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/oceania
>>
>
>
> --
> Alex Leith
> m: 0419189050
>


-- 
Dr. Adam Steer
http://spatialised.net
https://www.researchgate.net/profile/Adam_Steer
http://au.linkedin.com/in/adamsteer
http://orcid.org/0000-0003-0046-7236
+61 427 091 712 ::  @adamdsteer

Suits are bad for business: http://www.spatialised.net/business-penguins/
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