ST_WorldToRasterCoordX — Returns the column in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.
integer ST_WorldToRasterCoordX(raster  rast, geometry  pt);
integer ST_WorldToRasterCoordX(raster  rast, double precision  xw);
integer ST_WorldToRasterCoordX(raster  rast, double precision  xw, double precision  yw);
Returns the column in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw). A point, or (both xw and yw world coordinates are required if a raster is skewed). If a raster is not skewed then xw is sufficient. World coordinates are in the spatial reference coordinate system of the raster.
Changed: 2.1.0 In prior versions, this was called ST_World2RasterCoordX
SELECT rid, ST_WorldToRasterCoordX(rast,3427927.8) As xcoord,
		ST_WorldToRasterCoordX(rast,3427927.8,20.5) As xcoord_xwyw,
		ST_WorldToRasterCoordX(rast,ST_GeomFromText('POINT(3427927.8 20.5)',ST_SRID(rast))) As ptxcoord
FROM dummy_rast;
 rid | xcoord  |  xcoord_xwyw   | ptxcoord
-----+---------+---------+----------
   1 | 1713964 | 1713964 |  1713964
   2 |       1 |       1 |        1