ptarray_clamp_to_ordinate_range()

static POINTARRAY * ptarray_clamp_to_ordinate_range ( const POINTARRAY *  ipa, char  ordinate, double  from, double  to, uint8_t  is_closed  )

inlinestatic

Definition at line 441 of file lwlinearreferencing.c.

{
        POINT4D p1, p2;
        POINTARRAY *opa;
        double ovp1, ovp2;
        POINT4D *t;
        int8_t p1out, p2out; /* -1 - smaller than from, 0 - in range, 1 - larger than to */
        uint32_t i;
        uint8_t hasz = FLAGS_GET_Z(ipa->flags);
        uint8_t hasm = FLAGS_GET_M(ipa->flags);
 
        assert(from <= to);
 
        t = lwalloc(sizeof(POINT4D));
 
        /* Initial storage */
        opa = ptarray_construct_empty(hasz, hasm, ipa->npoints);
 
        /* Add first point */
        getPoint4d_p(ipa, 0, &p1);
        ovp1 = lwpoint_get_ordinate(&p1, ordinate);
 
        p1out = (ovp1 < from) ? -1 : ((ovp1 > to) ? 1 : 0);
 
        if (from <= ovp1 && ovp1 <= to)
                ptarray_append_point(opa, &p1, LW_FALSE);
 
        /* Loop on all other input points */
        for (i = 1; i < ipa->npoints; i++)
        {
                getPoint4d_p(ipa, i, &p2);
                ovp2 = lwpoint_get_ordinate(&p2, ordinate);
                p2out = (ovp2 < from) ? -1 : ((ovp2 > to) ? 1 : 0);
 
                if (p1out == 0 && p2out == 0) /* both visible */
                {
                        ptarray_append_point(opa, &p2, LW_FALSE);
                }
                else if (p1out == p2out && p1out != 0) /* both invisible on the same side */
                {
                        /* skip */
                }
                else if (p1out == -1 && p2out == 0)
                {
                        point_interpolate(&p1, &p2, t, hasz, hasm, ordinate, from);
                        ptarray_append_point(opa, t, LW_FALSE);
                        ptarray_append_point(opa, &p2, LW_FALSE);
                }
                else if (p1out == -1 && p2out == 1)
                {
                        point_interpolate(&p1, &p2, t, hasz, hasm, ordinate, from);
                        ptarray_append_point(opa, t, LW_FALSE);
                        point_interpolate(&p1, &p2, t, hasz, hasm, ordinate, to);
                        ptarray_append_point(opa, t, LW_FALSE);
                }
                else if (p1out == 0 && p2out == -1)
                {
                        point_interpolate(&p1, &p2, t, hasz, hasm, ordinate, from);
                        ptarray_append_point(opa, t, LW_FALSE);
                }
                else if (p1out == 0 && p2out == 1)
                {
                        point_interpolate(&p1, &p2, t, hasz, hasm, ordinate, to);
                        ptarray_append_point(opa, t, LW_FALSE);
                }
                else if (p1out == 1 && p2out == -1)
                {
                        point_interpolate(&p1, &p2, t, hasz, hasm, ordinate, to);
                        ptarray_append_point(opa, t, LW_FALSE);
                        point_interpolate(&p1, &p2, t, hasz, hasm, ordinate, from);
                        ptarray_append_point(opa, t, LW_FALSE);
                }
                else if (p1out == 1 && p2out == 0)
                {
                        point_interpolate(&p1, &p2, t, hasz, hasm, ordinate, to);
                        ptarray_append_point(opa, t, LW_FALSE);
                        ptarray_append_point(opa, &p2, LW_FALSE);
                }
 
                p1 = p2;
                p1out = p2out;
                LW_ON_INTERRUPT(ptarray_free(opa); return NULL);
        }
 
        if (is_closed && opa->npoints > 2)
        {
                getPoint4d_p(opa, 0, &p1);
                ptarray_append_point(opa, &p1, LW_FALSE);
        }
        lwfree(t);
 
        return opa;
}

References POINTARRAY::flags, FLAGS_GET_M, FLAGS_GET_Z, getPoint4d_p(), LW_FALSE, LW_ON_INTERRUPT, lwalloc(), lwfree(), lwpoint_get_ordinate(), POINTARRAY::npoints, point_interpolate(), ptarray_append_point(), ptarray_construct_empty(), and ptarray_free().

Referenced by lwpoly_clip_to_ordinate_range(), and lwtriangle_clip_to_ordinate_range().

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