lwgeom_remove_irrelevant_points_for_view()

void lwgeom_remove_irrelevant_points_for_view	(	LWGEOM *	geom,
		GBOX *	bbox,
		bool	cartesian_hint
	)

remove points that are irrelevant for rendering the geometry within a view specified by rectangular bounds.

2D-(MULTI)POLYGONs and (MULTI)LINESTRINGs are evaluated, others keep untouched.

Definition at line 318 of file liblwgeom/lwgeom_remove_irrelevant_points_for_view.c.

                                                                                             {
 
        unsigned int i, j, iw, jw;
 
        if (geom->type == LINETYPE) {
 
                LWLINE* line = (LWLINE*)geom;
                removePoints(line->points, bbox, false, cartesian_hint);
        }
 
        if (geom->type == MULTILINETYPE) {
 
                LWMLINE* mline = (LWMLINE*)geom;
                iw = 0;
                for (i=0; i<mline->ngeoms; i++) {
                        LWLINE* line = mline->geoms[i];
                        removePoints(line->points, bbox, false, cartesian_hint);
 
                        if (line->points->npoints) {
                                // keep (reduced) line
                                mline->geoms[iw++] = line;
                        }
                        else {
                                // discard current line
                                lwfree(line);
                        }
                }
                mline->ngeoms = iw;
        }
 
        if (geom->type == POLYGONTYPE) {
 
                LWPOLY* polygon = (LWPOLY*)geom;
                iw = 0;
                for (i=0; i<polygon->nrings; i++) {
                        removePoints(polygon->rings[i], bbox, true, cartesian_hint);
 
                        if (polygon->rings[i]->npoints) {
                                // keep (reduced) ring
                                polygon->rings[iw++] = polygon->rings[i];
                        }
                        else {
                                if (!i) {
                                        // exterior ring outside, free and skip all rings
                                        unsigned int k;
                                        for (k=0; k<polygon->nrings; k++) {
                                                lwfree(polygon->rings[k]);
                                        }
                                        break;
                                }
                                else {
                                        // free and remove current interior ring
                                        lwfree(polygon->rings[i]);
                                }
                        }
                }
                polygon->nrings = iw;
        }
 
        if (geom->type == MULTIPOLYGONTYPE) {
 
                LWMPOLY* mpolygon = (LWMPOLY*)geom;
                jw = 0;
                for (j=0; j<mpolygon->ngeoms; j++) {
 
                        LWPOLY* polygon = mpolygon->geoms[j];
                        iw = 0;
                        for (i=0; i<polygon->nrings; i++) {
                                removePoints(polygon->rings[i], bbox, true, cartesian_hint);
 
                                if (polygon->rings[i]->npoints) {
                                        // keep (reduced) ring
                                        polygon->rings[iw++] = polygon->rings[i];
                                }
                                else {
                                        if (!i) {
                                                // exterior ring outside, free and skip all rings
                                                unsigned int k;
                                                for (k=0; k<polygon->nrings; k++) {
                                                        lwfree(polygon->rings[k]);
                                                }
                                                break;
                                        }
                                        else {
                                                // free and remove current interior ring
                                                lwfree(polygon->rings[i]);
                                        }
                                }
                        }
                        polygon->nrings = iw;
 
                        if (iw) {
                                mpolygon->geoms[jw++] = polygon;
                        }
                        else {
                                // free and remove polygon from multipolygon
                                lwfree(polygon);
                        }
                }
                mpolygon->ngeoms = jw;
        }
}

References LWMLINE::geoms, LWMPOLY::geoms, LINETYPE, lwfree(), MULTILINETYPE, MULTIPOLYGONTYPE, LWMLINE::ngeoms, LWMPOLY::ngeoms, POINTARRAY::npoints, LWPOLY::nrings, LWLINE::points, POLYGONTYPE, removePoints(), LWPOLY::rings, and LWGEOM::type.

Referenced by ST_RemoveIrrelevantPointsForView(), and test_lwgeom_remove_irrelevant_points_for_view().

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