[postgis-tickets] [PostGIS] #5228: ST_MakeEmptyCoverage creates a bad tiling

[PostGIS]

#5228: ST_MakeEmptyCoverage creates a bad tiling
-------------------------+---------------------
 Reporter:  arthurbazin  |      Owner:  pramsey
     Type:  defect       |     Status:  new
 Priority:  medium       |  Milestone:
Component:  postgis      |    Version:  3.2.x
 Keywords:               |
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 When using ST_MakeEmptyCoverage the behaviour is really unexpected.

 When reading the documentation, I understand that if we provide a
 width/height and a tilewidth/tileheight, It create a set of tile with the
 same size (except for the tile on the border left and bottom) that
 fullfill the width/height.

 But when I'm using this function, I have tiles with different sizes wich
 follow an interesting pattern.

 Try with this request :

 {{{
 SELECT
   ST_Envelope(
         ST_MakeEmptyCoverage(
           1,  -- Tilewidth
           1,  -- Tileheight
           4,  -- Coverage width
           4,  -- Coverage height
           0,    -- X origin
           0,    -- Y origin
           1,    -- Scale X
           1,    -- Scale Y
           0,    -- Skew X
           0,    -- Skew Y
           4326  -- SRID
         )
   )
 }}}

 The result have 16 tiles :\\

 The 1st 4 tiles have the height of the coverage  \\

 The 2nd 4 tiles have an height of coverageheight - 1*tilewidth  \\

 The 3rd 4 tiles have an height of coverageheight - 2*tilewidth \\

 The 4th 4 tiles have an height of coverageheight - 3*tilewidth


 Maybe I don't understand how this function works but my expected result
 would be the result of this request :

 {{{
 SELECT
   ST_Envelope(
     ST_Tile(
       ST_MakeEmptyRaster(
         4,  -- Coverage width
         4,  -- Coverage height
         0,    -- X origin
         0,    -- Y origin
         1,    -- Scale X
         1,    -- Scale Y
         0,    -- Skew X
         0,    -- Skew Y
         4326  -- SRID
         ),
       1,
       1
     )
   )
 }}}
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5228>
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