[postgis-devel] ST_Rescale issues again

[Sandro Santilli]

On Thu, Aug 28, 2014 at 09:53:46AM +0200, Sandro Santilli wrote:
> I keep getting suprised by ST_Rescale/ST_Resample/etc outputs.
> What do you think about this.
> 
> 
> Original table tiles are fully aligned: 10x10 sized, all with scale 1,-1:
> 
>  =# select distinct st_scalex(r), st_scaley(r), st_width(r), st_height(r)
>  => from ( select r from res1 ) f;
>   st_scalex | st_scaley | st_width | st_height
>  -----------+-----------+----------+-----------
>           1 |        -1 |       10 |        10
>  (1 row)
> 
> Passing each of them through ST_Rescale with values 2.0, -2.0 result in
> some tiles getting the new scale requested and some not:
> 
>  =# select distinct st_scalex(r), st_scaley(r), st_width(r), st_height(r)
>  => from ( select ST_Rescale(r,2.0,-2.0) r from res1 ) f;
>   st_scalex | st_scaley | st_width | st_height
>  -----------+-----------+----------+-----------
>           2 |        -2 |        5 |         5
>           1 |        -1 |        5 |         5
>  (2 rows)
> 
> Why is that ?

I shall add that I get this warning 4 times:

 NOTICE:  Raster has default geotransform. Adjusting metadata for use of GDAL Warp API
 CONTEXT:  SQL function "st_rescale" statement 1

And that the deviant tile is a single one over a total of 648 tiles:

  count | st_scalex | st_scaley | st_width | st_height
 -------+-----------+-----------+----------+-----------
    647 |         2 |        -2 |        5 |         5
      1 |         1 |        -1 |        5 |         5
 (2 rows)

Should I file a ticket ?

--strk;