PostGIS  2.3.8dev-r@@SVN_REVISION@@

◆ rt_raster_get_convex_hull()

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 803 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().

803  {
804  double gt[6] = {0.0};
805  int srid = SRID_UNKNOWN;
806 
807  POINTARRAY *pts = NULL;
808  POINT4D p4d;
809 
810  assert(hull != NULL);
811  *hull = NULL;
812 
813  /* raster is NULL, convex hull is NULL */
814  if (raster == NULL)
815  return ES_NONE;
816 
817  /* raster metadata */
818  srid = rt_raster_get_srid(raster);
820 
821  RASTER_DEBUGF(3, "rt_raster_get_convex_hull: raster is %dx%d", raster->width, raster->height);
822 
823  /* return point or line since at least one of the two dimensions is 0 */
824  if ((!raster->width) || (!raster->height)) {
825  p4d.x = gt[0];
826  p4d.y = gt[3];
827 
828  /* return point */
829  if (!raster->width && !raster->height) {
830  LWPOINT *point = lwpoint_make2d(srid, p4d.x, p4d.y);
831  *hull = lwpoint_as_lwgeom(point);
832  }
833  /* return linestring */
834  else {
835  LWLINE *line = NULL;
836  pts = ptarray_construct_empty(0, 0, 2);
837 
838  /* first point of line */
839  ptarray_append_point(pts, &p4d, LW_TRUE);
840 
841  /* second point of line */
843  raster,
844  rt_raster_get_width(raster), rt_raster_get_height(raster),
845  &p4d.x, &p4d.y,
846  gt
847  ) != ES_NONE) {
848  rterror("rt_raster_get_convex_hull: Could not get second point for linestring");
849  return ES_ERROR;
850  }
851  ptarray_append_point(pts, &p4d, LW_TRUE);
852  line = lwline_construct(srid, NULL, pts);
853 
854  *hull = lwline_as_lwgeom(line);
855  }
856 
857  return ES_NONE;
858  }
859  else {
860  POINTARRAY **rings = NULL;
861  LWPOLY* poly = NULL;
862 
863  /* only one ring */
864  rings = (POINTARRAY **) rtalloc(sizeof (POINTARRAY*));
865  if (!rings) {
866  rterror("rt_raster_get_convex_hull: Could not allocate memory for polygon ring");
867  return ES_ERROR;
868  }
869  rings[0] = ptarray_construct(0, 0, 5);
870  /* TODO: handle error on ptarray construction */
871  /* XXX jorgearevalo: the error conditions aren't managed in ptarray_construct */
872  if (!rings[0]) {
873  rterror("rt_raster_get_convex_hull: Could not construct point array");
874  return ES_ERROR;
875  }
876  pts = rings[0];
877 
878  /* Upper-left corner (first and last points) */
879  p4d.x = gt[0];
880  p4d.y = gt[3];
881  ptarray_set_point4d(pts, 0, &p4d);
882  ptarray_set_point4d(pts, 4, &p4d);
883 
884  /* Upper-right corner (we go clockwise) */
886  raster,
887  raster->width, 0,
888  &p4d.x, &p4d.y,
889  gt
890  );
891  ptarray_set_point4d(pts, 1, &p4d);
892 
893  /* Lower-right corner */
895  raster,
896  raster->width, raster->height,
897  &p4d.x, &p4d.y,
898  gt
899  );
900  ptarray_set_point4d(pts, 2, &p4d);
901 
902  /* Lower-left corner */
904  raster,
905  0, raster->height,
906  &p4d.x, &p4d.y,
907  gt
908  );
909  ptarray_set_point4d(pts, 3, &p4d);
910 
911  poly = lwpoly_construct(srid, 0, 1, rings);
912  *hull = lwpoly_as_lwgeom(poly);
913  }
914 
915  return ES_NONE;
916 }
void ptarray_set_point4d(POINTARRAY *pa, int n, const POINT4D *p4d)
Definition: lwgeom_api.c:549
double x
Definition: liblwgeom.h:351
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:145
POINTARRAY * ptarray_construct_empty(char hasz, char hasm, uint32_t maxpoints)
Create a new POINTARRAY with no points.
Definition: ptarray.c:70
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
gt
Definition: window.py:77
LWGEOM * lwpoly_as_lwgeom(const LWPOLY *obj)
Definition: lwgeom.c:252
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:262
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_FALSE, 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:43
#define LW_TRUE
Return types for functions with status returns.
Definition: liblwgeom.h:75
LWLINE * lwline_construct(int srid, GBOX *bbox, POINTARRAY *points)
Definition: lwline.c:42
uint16_t width
Definition: librtcore.h:2264
#define SRID_UNKNOWN
Unknown SRID value.
Definition: liblwgeom.h:187
#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:267
uint16_t rt_raster_get_height(rt_raster raster)
Definition: rt_raster.c:129
double y
Definition: liblwgeom.h:351
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