[postgis-users] Newbie ST_World2RasterCoordX, ST_World2RasterCoordY Band Values nested loop to iterate over raster

[Chris English]

Hi,

I am trying to iterate over a raster, extract World2RasterCoordX/Y and Band
Values using the following function:

Create or replace function extract_as_text(rast raster) returns text as
$$
Declare
 i int;
 j int;
rast raster;

Begin
for i in 1..2048 loop  --dim x
for j in 1..1536 loop -- dim y
select ST_world2rastercoordx(rast, i, j) as xcoord,
St_world2rastercoordy(rast, i, j) as ycoord,
ST_value(rast,1, i, j) as R,
ST_value(rast, 2, i, j) as G,
ST_value(rast, 3, i, j) as B
from rbike_all;
End loop;
End loop;
return xcoord,ycoord,R,G,B; <- this part is probably not right either -
should perhaps just say text
end;
$$
Language 'plpgsql'

Query returned successfully with no result in 15 ms.

Select extract_as_text(rast)
from rbike_all;

ERROR:  column reference "rast" is ambiguous
LINE 1: select ST_world2rastercoordx(rast, i, j) as xcoord,
                                     ^
DETAIL:  It could refer to either a PL/pgSQL variable or a table column.
QUERY:  select ST_world2rastercoordx(rast, i, j) as xcoord,
St_world2rastercoordy(rast, i, j) as ycoord,
ST_value(rast,1, i, j) as R,
ST_value(rast, 2, i, j) as G,
ST_value(rast, 3, i, j) as B
from rbike_all
CONTEXT:  PL/pgSQL function "extract_as_text" line 9 at SQL statement


********** Error **********

ERROR: column reference "rast" is ambiguous
SQL state: 42702
Detail: It could refer to either a PL/pgSQL variable or a table column.
Context: PL/pgSQL function "extract_as_text" line 9 at SQL statement

Removing rast from Declare above  results in the same error.

Any pointers greatly appreciated.

Chris

-- 
He doesn't fully understand what he thinks he knows about the problem.
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