ptarray_chaikin()

static POINTARRAY * ptarray_chaikin ( POINTARRAY *  inpts, int  preserve_endpoint, int  isclosed  )

static

Definition at line 31 of file lwchaikins.c.

{
        uint32_t p, i, n_out_points=0, p1_set=0, p2_set=0;
        POINT4D p1, p2;
        POINTARRAY *opts;
        double *dlist;
        double deltaval, quarter_delta, val1, val2;
        uint32_t ndims = 2 + ptarray_has_z(inpts) + ptarray_has_m(inpts);
        int new_npoints = inpts->npoints * 2;
        opts = ptarray_construct_empty(FLAGS_GET_Z(inpts->flags), FLAGS_GET_M(inpts->flags), new_npoints);
 
        dlist = (double*)(opts->serialized_pointlist);
 
        p1 = getPoint4d(inpts, 0);
        /*if first point*/
        if(preserve_endpoint)
        {
                ptarray_append_point(opts, &p1, LW_TRUE);
                n_out_points++;
        }
 
        for (p=1;p<inpts->npoints;p++)
        {
                memcpy(&p2, &p1, sizeof(POINT4D));
                p1 = getPoint4d(inpts, p);
                if(p>0)
                {
                        p1_set = p2_set = 0;
                        for (i=0;i<ndims;i++)
                        {
                                val1 = ((double*) &(p1))[i];
                                val2 = ((double*) &(p2))[i];
                                deltaval =  val1 - val2;
                                quarter_delta = deltaval * 0.25;
                                if(!preserve_endpoint || p > 1)
                                {
                                        dlist[n_out_points * ndims + i] = val2 + quarter_delta;
                                        p1_set = 1;
                                }
                                if(!preserve_endpoint || p < inpts->npoints - 1)
                                {
                                        dlist[(n_out_points + p1_set) * ndims + i] = val1 - quarter_delta;
                                        p2_set = 1;
                                }
                        }
                        n_out_points+=(p1_set + p2_set);
                }
        }
 
        /*if last point*/
        if(preserve_endpoint)
        {
                opts->npoints = n_out_points;
                ptarray_append_point(opts, &p1, LW_TRUE);
                n_out_points++;
        }
 
        if(isclosed && !preserve_endpoint)
        {
                opts->npoints = n_out_points;
                POINT4D first_point = getPoint4d(opts, 0);
                ptarray_append_point(opts, &first_point, LW_TRUE);
                n_out_points++;
        }
        opts->npoints = n_out_points;
 
        return opts;
 
}

References POINTARRAY::flags, FLAGS_GET_M, FLAGS_GET_Z, getPoint4d(), LW_TRUE, POINTARRAY::npoints, ptarray_append_point(), ptarray_construct_empty(), ptarray_has_m(), and ptarray_has_z().

Referenced by lwline_chaikin(), and lwpoly_chaikin().

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