[postgis-tickets] [PostGIS] #2832: [raster] raster2pgsql pads overviews with single tiles

[PostGIS]

#2832: [raster] raster2pgsql pads overviews with single tiles
--------------------+-------------------------------------------------------
 Reporter:  strk    |       Owner:  dustymugs
     Type:  defect  |      Status:  new      
 Priority:  medium  |   Milestone:           
Component:  raster  |     Version:  trunk    
 Keywords:          |  
--------------------+-------------------------------------------------------
 I'm importing
 https://github.com/mapnik/mapnik/blob/v2.2.0/tests/data/raster/dataraster.tif
 with overviews 4 and 16 using raster2pgsql, requesting no padding:
 {{{
 raster2pgsql -l 4,16 -t 256x256 dataraster.tif dataraster
 }}}

 The import results in 3 tables: dataraster (72 rows), o_4_dataraster (6
 rows), o_16_dataraster (1 row).

 While the o_4_dataraster tiles are correctly NOT padded, the
 o_16_dataraster tile is instead fully padded.

 So we have, for o_4_dataraster:
 {{{
 mapnik-tmp-pgraster-test-db=# select st_summary(rast) from o_4_dataraster;
                                       st_summary
 ---------------------------------------------------------------------------------------
  Raster of 256x256 pixels has 1 band and extent of BOX(-14637
 4347678,497363 4859678) +
      band 1 of pixtype 16BSI is in-db with NODATA value of -999
  Raster of 256x256 pixels has 1 band and extent of BOX(497363
 4347678,1009363 4859678)+
      band 1 of pixtype 16BSI is in-db with NODATA value of -999
  Raster of 59x256 pixels has 1 band and extent of BOX(1009363
 4347678,1127363 4859678)+
      band 1 of pixtype 16BSI is in-db with NODATA value of -999
  Raster of 256x222 pixels has 1 band and extent of BOX(-14637
 3903678,497363 4347678) +
      band 1 of pixtype 16BSI is in-db with NODATA value of -999
  Raster of 256x222 pixels has 1 band and extent of BOX(497363
 3903678,1009363 4347678)+
      band 1 of pixtype 16BSI is in-db with NODATA value of -999
  Raster of 59x222 pixels has 1 band and extent of BOX(1009363
 3903678,1127363 4347678)+
      band 1 of pixtype 16BSI is in-db with NODATA value of -999
 (6 rows)
 }}}

 And for o_16_dataraster:
 {{{
 mapnik-tmp-pgraster-test-db=# select st_summary(rast) from
 o_16_dataraster;
                                       st_summary
 ---------------------------------------------------------------------------------------
  Raster of 256x256 pixels has 1 band and extent of BOX(-14637
 2811678,2033363 4859678)+
      band 1 of pixtype 16BSI is in-db with NODATA value of -999
 (1 row)
 }}}

 The problem with the padding is that the extent of the overview with
 factor 16 is a lot larger than the original extent:
 {{{
 mapnik-tmp-pgraster-test-db=# select 'orig' as l,
 st_extent(rast::geometry) from dataraster union all select 'ov_4',
 st_extent(rast::geometry) from o_4_dataraster union all select 'o_16',
 st_extent(rast::geometry) from o_16_dataraster;
   l   |              st_extent
 ------+-------------------------------------
  orig | BOX(-14637 3903178,1126863 4859678)
  ov_4 | BOX(-14637 3903678,1127363 4859678)
  o_16 | BOX(-14637 2811678,2033363 4859678)
 (3 rows)
 }}}

 That is, the extent of overview 16 covers almost 4 times the area of the
 original geometry, while the extent of overview 4 is almost the same:
 {{{
 mapnik-tmp-pgraster-test-db=# with p as ( select ( select
 st_extent(rast::geometry) from dataraster ) as orig, ( select
 st_extent(rast::geometry) from o_4_dataraster ) as o4, ( select
 st_extent(rast::geometry) from o_16_dataraster ) o16 ) select
 st_area(o4)/st_area(orig) as o4f, st_area(o16)/st_area(orig) as o16f from
 p;
 -[ RECORD 1 ]-----------
 o4f  | 0.999915052025483
 o16f | 3.84148387396651
 }}}

 I'm actually also surprised to see that the area of extent for overview 4
 is even slightly smaller than the area of the original extent.

 Anyway, this ticket is for the forced padding in the single-tile overview.

 I hadn't tried with versions less than 2.2.0dev

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2832>
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