[gdal-dev] gdaladdo does not "respect" GPKG tile matrix

[Philippe Ghesquiere]

Dear all,
 A while ago, I opened a ticket which is still opened (
https://github.com/OSGeo/gdal/issues/3853). I recently  bumped into this
bug with some new data, and I think I tracked the origin.


*1) Generate a test image :*
gdal_create -of GTIFF -co COMPRESS=LZW -a_srs epsg:4326 -a_ullr -180 90 180
-90 -burn 128 -outsize 2048 1024 worldwide.tif

*2) Convert to GPKG :*
 gdal_translate -of GPKG -co TILING_SCHEME=InspireCRS84Quad worldwide.tif
worldwide_no_pyramid.gpkg

The GPKG tile matrix is as expected :
sqlite3 -header -column worldwide_no_pyramid.gpkg "SELECT rowid,* FROM
gpkg_tile_matrix  ;"
rowid  table_name            zoom_level  matrix_width  matrix_height
 tile_width  tile_height  pixel_x_size  pixel_y_size
-----  --------------------  ----------  ------------  -------------
 ----------  -----------  ------------  ------------
1      worldwide_no_pyramid  0           2             1              256
      256          0.703125      0.703125
2      worldwide_no_pyramid  1           4             2              256
      256          0.3515625     0.3515625
3      worldwide_no_pyramid  2           8             4              256
      256          0.17578125    0.17578125

*3) Compute a default pyramid:*
cp worldwide_no_pyramid.gpkg worldwide_default_pyramid.gpkg
gdaladdo worldwide_default_pyramid.gpkg

The GPKG tile matrix is no longer the expected one (InspireCRS84Quad
InspireCRS84Quad) :
sqlite3 -header -column worldwide_default_pyramid.gpkg  "SELECT rowid,*
FROM gpkg_tile_matrix  ;"
rowid  table_name            zoom_level  matrix_width  matrix_height
 tile_width  tile_height  pixel_x_size  pixel_y_size
-----  --------------------  ----------  ------------  -------------
 ----------  -----------  ------------  ------------
1      worldwide_no_pyramid  1           2             1              256
      256          0.703125      0.703125
2      worldwide_no_pyramid  2           4             2              256
      256          0.3515625     0.3515625
3      worldwide_no_pyramid  3           8             4              256
      256          0.17578125    0.17578125
4      worldwide_no_pyramid  0           1             1              256
      256          1.40625       1.40625

*4) Compute a manual pyramid:*
cp worldwide_no_pyramid.gpkg worldwide_manual_pyramid.gpkg
gdaladdo worldwide_manual_pyramid.gpkg 2 4

The GPKG tile matrix is still as expected (InspireCRS84Quad
InspireCRS84Quad) :
sqlite3 -header -column worldwide_manual_pyramid.gpkg  "SELECT rowid,* FROM
gpkg_tile_matrix  ;"
rowid  table_name            zoom_level  matrix_width  matrix_height
 tile_width  tile_height  pixel_x_size  pixel_y_size
-----  --------------------  ----------  ------------  -------------
 ----------  -----------  ------------  ------------
1      worldwide_no_pyramid  0           2             1              256
      256          0.703125      0.703125
2      worldwide_no_pyramid  1           4             2              256
      256          0.3515625     0.3515625
3      worldwide_no_pyramid  2           8             4              256
      256          0.17578125    0.17578125

*5) Compute a "Weird" pyramid:*
In this test, I generate too many levels in the pyramid on purpose :
cp worldwide_no_pyramid.gpkg worldwide_manual_weird_pyramid.gpkg
gdaladdo worldwide_manual_weird_pyramid.gpkg 2 4 8

The GPKG tile matrix is exactly the same as in
worldwide_default_pyramid.gpkg :
sqlite3 -header -column worldwide_manual_weird_pyramid.gpkg  "SELECT
rowid,* FROM gpkg_tile_matrix  ;"
rowid  table_name            zoom_level  matrix_width  matrix_height
 tile_width  tile_height  pixel_x_size  pixel_y_size
-----  --------------------  ----------  ------------  -------------
 ----------  -----------  ------------  ------------
1      worldwide_no_pyramid  1           2             1              256
      256          0.703125      0.703125
2      worldwide_no_pyramid  2           4             2              256
      256          0.3515625     0.3515625
3      worldwide_no_pyramid  3           8             4              256
      256          0.17578125    0.17578125
4      worldwide_no_pyramid  0           1             1              256
      256          1.40625       1.40625

*6) Conclusion *
The default power-of-two factor list is computed in gdaladdo.cpp. At this
point, the algorithm is not aware of some GPKG limitations.

I found two workarounds :

   - specify explicitly all zoom levels
   - add minsize option. The minimum size has to be twice the tile_height /
   tile_width : -minsize 512

Shouldn't we have a specific check for GPKG while computing the pyramid ?
For example by deriving the virtual method BuildOverviews() for GPKG ?

Philippe
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