[Geopackage] Tile dimensions

Even Rouault even.rouault at spatialys.com
Sat Dec 10 07:40:55 EST 2016


Hi,

AFAICS nothing in the spec strongly binds (ie as a requirement or a test in the ATS) the values 
of (tile_width, tile_height) found in gpkg_tile_matrix with the actual dimensions of the 
images stored in the tile pyramid user data table. Table 10 mentions though tile_matrix : 
"Tile width in pixels (>= 1)for this zoom level" (and similar for tile_height).

Is there an implicit requirement that the dimensions of images in the tile pyramid user data 
table should be exactly (tile_width, tile_height) ? 

Making them greater than that does not make sense of course, but one could imagine that 
for images at the right or bottom border of a raster coverage to be truncated. For example if 
you have a raster of size 300x300 with tiles of 256x256, the right tile could be just 44 pixel 
wide. Would that be valid ? If not, perhaps that could be mentionned ("tiles should not be 
truncated, but padded to reach the tile_width x tile_height dimensions")

Even

-- 
Spatialys - Geospatial professional services
http://www.spatialys.com
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