[postgis-devel] Missing something simple

[Nathaniel Clay]

Hi all,

I am developing a function that takes in two points on a raster and returns
a line from one to the other consisting of the pixel values between the two
points in the z ordinate in the form of a lwline. However, I am getting a
Sig Bus error.

1) Is there any interest in a function like this?
2) I've looked through other similar functions in the doxygen
documentation, and I can't see what I am missing that is causing the error.
Any help would be appreciated.

{{{

/*
  ST_Profile
*/

PG_FUNCTION_INFO_V1(RASTER_profile);
Datum RASTER_profile(PG_FUNCTION_ARGS)
{
    rt_pgraster *pgraster;
    rt_raster raster;
    rt_band band;

    LWLINE *rtnline;
    LWPOINT *point;

    double value;
    int nodata;
    int bandn;

    double gt;
    double xw,yw;
    int where =0;
    int error, err,e2;
    int x0, x1, y0, y1, dx, dy, sx, sy;
    int32_t srid;

     /* Deserialize raster */
          if (PG_ARGISNULL(0)) PG_RETURN_NULL();
          pgraster = (rt_pgraster *)PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
      bandn = PG_GETARG_INT32(1);
      x0 = PG_GETARG_INT32(2);
      y0 = PG_GETARG_INT32(3);
      x1 = PG_GETARG_INT32(4);
      y1 = PG_GETARG_INT32(5);

          raster = rt_raster_deserialize(pgraster, FALSE);
          if (!raster) {
              elog(ERROR, "RASTER_profile: Could not deserialize raster");
              PG_FREE_IF_COPY(pgraster, 0);
             PG_RETURN_NULL();
          }
      srid = rt_raster_get_srid(raster);
      rtnline = lwline_construct_empty(srid,true,false);
      rt_raster_get_geotransform_matrix(raster,&gt);
      band = rt_raster_get_band(raster, bandn - 1);

      dx = abs(x1-x0);
      sx = x0<x1 ? 1 : -1;
      dy = abs(y1-y0);
      sy = y0<y1 ? 1 : -1;
      err = (dx>dy ? dx : -dy)/2;

        for(;;){

              error = rt_band_get_pixel(band,x0,y0,&value,&nodata);


             if( error != 0 ) {
           elog(ERROR,"RASTER_Profile: Could not get value for pixel");
           PG_FREE_IF_COPY(pgraster,0);
           PG_RETURN_NULL();
                  }
         if (!nodata){

rt_raster_cell_to_geopoint(raster,(double)x0,(double)y0,&xw,&yw,&gt);
         point = lwpoint_make3dz(srid,xw,yw,value);
         lwline_add_lwpoint(rtnline,point,where);
         where++;
         }

            if (x0==x1 && y0==y1) break;
            e2 = err;
            if (e2 >-dx) { err -= dy; x0 += sx; }
            if (e2 < dy) { err += dx; y0 += sy; }
        }


    PG_RETURN_POINTER(geometry_serialize(lwline_as_lwgeom(rtnline)));

}
}}}

Thanks,

Nathaniel Hunter Clay
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