ST_RasterToWorldCoord — Returns the raster's upper left corner as geometric X and Y (longitude and latitude) given a column and row. Column and row starts at 1.
record ST_RasterToWorldCoord(raster rast, integer xcolumn, integer yrow);
Returns the upper left corner as geometric X and Y (longitude and latitude) given a column and row. Returned X and Y are in geometric units of the georeferenced raster. Numbering of column and row starts at 1 but if either parameter is passed a zero, a negative number or a number greater than the respective dimension of the raster, it will return coordinates outside of the raster assuming the raster's grid is applicable outside the raster's bounds.
Availability: 2.1.0
-- non-skewed raster
SELECT
rid,
(ST_RasterToWorldCoord(rast,1, 1)).*,
(ST_RasterToWorldCoord(rast,2, 2)).*
FROM dummy_rast
rid | longitude | latitude | longitude | latitude
-----+------------+----------+-----------+------------
1 | 0.5 | 0.5 | 2.5 | 3.5
2 | 3427927.75 | 5793244 | 3427927.8 | 5793243.95
-- skewed raster
SELECT
rid,
(ST_RasterToWorldCoord(rast, 1, 1)).*,
(ST_RasterToWorldCoord(rast, 2, 3)).*
FROM (
SELECT
rid,
ST_SetSkew(rast, 100.5, 0) As rast
FROM dummy_rast
) As foo
rid | longitude | latitude | longitude | latitude
-----+------------+----------+-----------+-----------
1 | 0.5 | 0.5 | 203.5 | 6.5
2 | 3427927.75 | 5793244 | 3428128.8 | 5793243.9