PostGIS  2.2.7dev-r@@SVN_REVISION@@
rt_errorstate rt_raster_get_convex_hull ( rt_raster  raster,
LWGEOM **  hull 
)

Get raster's convex hull.

The convex hull is a 4 vertices (5 to be closed) single ring polygon bearing the raster's rotation and using projection coordinates.

Parameters
raster: the raster to get info from
**hull: pointer to convex hull
Returns
ES_NONE if success, ES_ERROR if error

The convex hull is typically a 4 vertices (5 to be closed) single ring polygon bearing the raster's rotation and using projection coordinates.

Parameters
raster: the raster to get info from
**hull: pointer to convex hull
Returns
ES_NONE if success, ES_ERROR if error

Definition at line 822 of file rt_geometry.c.

References ES_ERROR, ES_NONE, window::gt, rt_raster_t::height, LW_TRUE, lwline_as_lwgeom(), lwline_construct(), lwpoint_as_lwgeom(), lwpoint_make2d(), lwpoly_as_lwgeom(), lwpoly_construct(), ptarray_append_point(), ptarray_construct(), ptarray_construct_empty(), ptarray_set_point4d(), RASTER_DEBUGF, rt_raster_cell_to_geopoint(), rt_raster_get_geotransform_matrix(), rt_raster_get_height(), rt_raster_get_srid(), rt_raster_get_width(), rtalloc(), rterror(), SRID_UNKNOWN, rt_raster_t::width, POINT4D::x, and POINT4D::y.

Referenced by RASTER_clip(), RASTER_convex_hull(), rt_raster_compute_skewed_raster(), rt_raster_intersects(), rt_raster_surface(), and test_raster_convex_hull().

822  {
823  double gt[6] = {0.0};
824  int srid = SRID_UNKNOWN;
825 
826  POINTARRAY *pts = NULL;
827  POINT4D p4d;
828 
829  assert(hull != NULL);
830  *hull = NULL;
831 
832  /* raster is NULL, convex hull is NULL */
833  if (raster == NULL)
834  return ES_NONE;
835 
836  /* raster metadata */
837  srid = rt_raster_get_srid(raster);
839 
840  RASTER_DEBUGF(3, "rt_raster_get_convex_hull: raster is %dx%d", raster->width, raster->height);
841 
842  /* return point or line since at least one of the two dimensions is 0 */
843  if ((!raster->width) || (!raster->height)) {
844  p4d.x = gt[0];
845  p4d.y = gt[3];
846 
847  /* return point */
848  if (!raster->width && !raster->height) {
849  LWPOINT *point = lwpoint_make2d(srid, p4d.x, p4d.y);
850  *hull = lwpoint_as_lwgeom(point);
851  }
852  /* return linestring */
853  else {
854  LWLINE *line = NULL;
855  pts = ptarray_construct_empty(0, 0, 2);
856 
857  /* first point of line */
858  ptarray_append_point(pts, &p4d, LW_TRUE);
859 
860  /* second point of line */
862  raster,
863  rt_raster_get_width(raster), rt_raster_get_height(raster),
864  &p4d.x, &p4d.y,
865  gt
866  ) != ES_NONE) {
867  rterror("rt_raster_get_convex_hull: Could not get second point for linestring");
868  return ES_ERROR;
869  }
870  ptarray_append_point(pts, &p4d, LW_TRUE);
871  line = lwline_construct(srid, NULL, pts);
872 
873  *hull = lwline_as_lwgeom(line);
874  }
875 
876  return ES_NONE;
877  }
878  else {
879  POINTARRAY **rings = NULL;
880  LWPOLY* poly = NULL;
881 
882  /* only one ring */
883  rings = (POINTARRAY **) rtalloc(sizeof (POINTARRAY*));
884  if (!rings) {
885  rterror("rt_raster_get_convex_hull: Could not allocate memory for polygon ring");
886  return ES_ERROR;
887  }
888  rings[0] = ptarray_construct(0, 0, 5);
889  /* TODO: handle error on ptarray construction */
890  /* XXX jorgearevalo: the error conditions aren't managed in ptarray_construct */
891  if (!rings[0]) {
892  rterror("rt_raster_get_convex_hull: Could not construct point array");
893  return ES_ERROR;
894  }
895  pts = rings[0];
896 
897  /* Upper-left corner (first and last points) */
898  p4d.x = gt[0];
899  p4d.y = gt[3];
900  ptarray_set_point4d(pts, 0, &p4d);
901  ptarray_set_point4d(pts, 4, &p4d);
902 
903  /* Upper-right corner (we go clockwise) */
905  raster,
906  raster->width, 0,
907  &p4d.x, &p4d.y,
908  gt
909  );
910  ptarray_set_point4d(pts, 1, &p4d);
911 
912  /* Lower-right corner */
914  raster,
915  raster->width, raster->height,
916  &p4d.x, &p4d.y,
917  gt
918  );
919  ptarray_set_point4d(pts, 2, &p4d);
920 
921  /* Lower-left corner */
923  raster,
924  0, raster->height,
925  &p4d.x, &p4d.y,
926  gt
927  );
928  ptarray_set_point4d(pts, 3, &p4d);
929 
930  poly = lwpoly_construct(srid, 0, 1, rings);
931  *hull = lwpoly_as_lwgeom(poly);
932  }
933 
934  return ES_NONE;
935 }
void ptarray_set_point4d(POINTARRAY *pa, int n, const POINT4D *p4d)
Definition: lwgeom_api.c:536
double x
Definition: liblwgeom.h:336
POINTARRAY * ptarray_construct(char hasz, char hasm, uint32_t npoints)
Construct an empty pointarray, allocating storage and setting the npoints, but not filling in any inf...
Definition: ptarray.c:62
void rt_raster_get_geotransform_matrix(rt_raster raster, double *gt)
Get 6-element array of raster geotransform matrix.
Definition: rt_raster.c:706
LWPOINT * lwpoint_make2d(int srid, double x, double y)
Definition: lwpoint.c:132
POINTARRAY * ptarray_construct_empty(char hasz, char hasm, uint32_t maxpoints)
Create a new POINTARRAY with no points.
Definition: ptarray.c:70
tuple gt
Definition: window.py:77
void rterror(const char *fmt,...)
Wrappers used for reporting errors and info.
Definition: rt_context.c:199
void * rtalloc(size_t size)
Wrappers used for managing memory.
Definition: rt_context.c:171
LWGEOM * lwpoly_as_lwgeom(const LWPOLY *obj)
Definition: lwgeom.c:239
uint16_t height
Definition: librtcore.h:2265
rt_errorstate rt_raster_cell_to_geopoint(rt_raster raster, double xr, double yr, double *xw, double *yw, double *gt)
Convert an xr, yr raster point to an xw, yw point on map.
Definition: rt_raster.c:755
LWGEOM * lwline_as_lwgeom(const LWLINE *obj)
Definition: lwgeom.c:249
int ptarray_append_point(POINTARRAY *pa, const POINT4D *pt, int allow_duplicates)
Append a point to the end of an existing POINTARRAY If allow_duplicate is LW_TRUE, then a duplicate point will not be added.
Definition: ptarray.c:156
LWPOLY * lwpoly_construct(int srid, GBOX *bbox, uint32_t nrings, POINTARRAY **points)
Definition: lwpoly.c:29
#define LW_TRUE
Return types for functions with status returns.
Definition: liblwgeom.h:61
LWLINE * lwline_construct(int srid, GBOX *bbox, POINTARRAY *points)
Definition: lwline.c:29
uint16_t width
Definition: librtcore.h:2264
#define SRID_UNKNOWN
Unknown SRID value.
Definition: liblwgeom.h:172
#define RASTER_DEBUGF(level, msg,...)
Definition: librtcore.h:311
int32_t rt_raster_get_srid(rt_raster raster)
Get raster's SRID.
Definition: rt_raster.c:356
uint16_t rt_raster_get_width(rt_raster raster)
Definition: rt_raster.c:121
LWGEOM * lwpoint_as_lwgeom(const LWPOINT *obj)
Definition: lwgeom.c:254
uint16_t rt_raster_get_height(rt_raster raster)
Definition: rt_raster.c:129
double y
Definition: liblwgeom.h:336

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