ptarray_simplify()

POINTARRAY* ptarray_simplify	(	POINTARRAY *	inpts,
		double	epsilon,
		unsigned int	minpts
	)

Parameters

minpts

minimun number of points to retain, if possible.

Definition at line 1601 of file ptarray.c.

References POINTARRAY::flags, FLAGS_GET_M, FLAGS_GET_Z, FLAGS_NDIMS, getPoint4d_p(), LW_FALSE, lwalloc(), LWDEBUG, LWDEBUGF, lwfree(), POINTARRAY::npoints, ptarray_append_point(), ptarray_construct_empty(), and ptarray_dp_findsplit().

Referenced by lwline_simplify(), and lwpoly_simplify().

{
        int *stack;                     /* recursion stack */
        int sp=-1;                      /* recursion stack pointer */
        int p1, split;
        double dist;
        POINTARRAY *outpts;
        POINT4D pt;

        double eps_sqr = epsilon * epsilon;

        /* Allocate recursion stack */
        stack = lwalloc(sizeof(int)*inpts->npoints);

        p1 = 0;
        stack[++sp] = inpts->npoints-1;

        LWDEBUGF(2, "Input has %d pts and %d dims", inpts->npoints,
                                                    FLAGS_NDIMS(inpts->flags));

        /* Allocate output POINTARRAY, and add first point. */
        outpts = ptarray_construct_empty(FLAGS_GET_Z(inpts->flags), FLAGS_GET_M(inpts->flags), inpts->npoints);
        getPoint4d_p(inpts, 0, &pt);
        ptarray_append_point(outpts, &pt, LW_FALSE);

        LWDEBUG(3, "Added P0 to simplified point array (size 1)");

        do
        {

                ptarray_dp_findsplit(inpts, p1, stack[sp], &split, &dist);

                LWDEBUGF(3, "Farthest point from P%d-P%d is P%d (dist. %g)", p1, stack[sp], split, dist);

                if (dist > eps_sqr || ( outpts->npoints+sp+1 < minpts && dist >= 0 ) )
                {
                        LWDEBUGF(4, "Added P%d to stack (outpts:%d)", split, sp);
                        stack[++sp] = split;
                }
                else
                {
                        getPoint4d_p(inpts, stack[sp], &pt);
                        LWDEBUGF(4, "npoints , minpoints %d %d", outpts->npoints, minpts);
                        ptarray_append_point(outpts, &pt, LW_FALSE);

                        LWDEBUGF(4, "Added P%d to simplified point array (size: %d)", stack[sp], outpts->npoints);

                        p1 = stack[sp--];
                }

                LWDEBUGF(4, "stack pointer = %d", sp);
        }
        while (! (sp<0) );

        lwfree(stack);
        return outpts;
}

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