>Given that the modules are unsupported and not working properly anyways, I'd
>>rather fix things to follow GDAL's approach.
No objection. If two open source GIS software under the OSGeo umbrella do
something in the same way we can start calling it as a de facto standard.
Even has been committing a lot to GPKG lately but mostly to the vector side. It
might still be good to check if GDAL still follows the same approach as you are
planning to follow.
Andrea Aime wrote:
[Geoserver-devel] Geopackage tiles generation issues
I am looking into why the raster geopackages GeoServer generates via the
geopackage module are not
being read correctly by gdal and found a few issues, some straight bugs, other
more like odd design decisions.
The straight bug is what's causing GDAL not to read the files correctly, the
current code, shared with mbtiles
generation, forces the request to be cast on a GWC managed gridset (and
actually works only if the requested
layers are cached, which is a bit of a nonsense to me given this is a WMS
request...), and uses that gridset
coordinates for tiles.
Now the problem is that in the geopackage metadata for the layer and the
gridset we are declaring the requested bbox, not the
ones used for tiles generation, resulting in tile coordinates being off the
Now, geopackage natively has the layer bounds that are separate from the tile
matrix ones, but the current geotools code
forces them to be the same.. that's a limitation I'm fixing.
However, the main issue remains... if someone asks for a layer in a certain
SRS, why try to coax it into a tile matrix managed
I believe the intention was to try and leverage GWC cache, but still, while I
understand taking the opportunity if possible, in
my opinion the request of the user should be respected, and if the request is
not a match either by SRS or BBOX to a tileset,
GeoServer should not force a different response.
From the same line of thought, a WMS request should not fail if it's made
against a layer that is not cached by GWC, like it
does today, with a strange error message too, e.g. asking for UTM 32N, which is
not tile cached:
java.lang.IllegalArgumentException: Thread 19276 Unknown layer nurc:mosaic.
Check the logfiles, it may not have loaded properly
The second thing that I find confusing is, if I asked for a result image that's
768 pixels wide, why am I getting back a geopackage that's
over 100000 pixels wide? That's... insane, especially for a WMS request (large
jobs should be deferred to WPS asynch requests).
Looking at the code, there is logic that generates the min and max zoom levels
for the tile matrix, and it does something rather surprising...
it picks the zoom level closest to the requested one as the min zoom level, and
then starts adding zoom levels until the matrix
has (stricly) more than 256 tiles in width... in my case, that means 512 tiles,
or a total width of 512*256=131072 pixels!
Trying GDAL on the command line, translating from a geotiff to a geopackage, it
makes what looks like a more sensible choice instead: it uses the
requested zoom level as the _maximum_ one, and then adds overviews to it, in
the cases I've tried, until a single tile is left (basically, a good
output with overviews). With our case we can also generate raster geopackages
out of vector layers, and creating the overviews might end up
hitting badly setup styles displaying too much data, but still, that would be a
problem also in random WMS requests, so I'm not too concerned...
Also, by default, GDAL generates a gridset that's an exact match for the source
data, meaning a custom one. That also makes sense to me, if someone
wants something other than the BBOX/SRS requested there are format options to
choose both the target gridset and min/max zoom levels.
Given that the modules are unsupported and not working properly anyways, I'd
rather fix things to follow GDAL's approach.
GeoServer Professional Services from the experts! Visit
http://goo.gl/it488V for more information.
Ing. Andrea Aime
Via di Montramito 3/A
55054 Massarosa (LU)
phone: +39 0584 962313
fax: +39 0584 1660272
mob: +39 339 8844549
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