lw_arc_calculate_gbox_cartesian_2d()

int lw_arc_calculate_gbox_cartesian_2d	(	const POINT2D *	A1,
		const POINT2D *	A2,
		const POINT2D *	A3,
		GBOX *	gbox
	)

Definition at line 464 of file g_box.c.

References FP_MAX, FP_MIN, lw_arc_center(), lw_segment_side(), LW_SUCCESS, LWDEBUG, POINT2D::x, GBOX::xmax, GBOX::xmin, POINT2D::y, GBOX::ymax, and GBOX::ymin.

Referenced by lw_arc_calculate_gbox_cartesian(), and ptarrayarc_contains_point_partial().

{
        POINT2D xmin, ymin, xmax, ymax;
        POINT2D C;
        int A2_side;
        double radius_A;

        LWDEBUG(2, "lw_arc_calculate_gbox_cartesian_2d called.");

        radius_A = lw_arc_center(A1, A2, A3, &C);

        /* Negative radius signals straight line, p1/p2/p3 are colinear */
        if (radius_A < 0.0)
        {
        gbox->xmin = FP_MIN(A1->x, A3->x);
        gbox->ymin = FP_MIN(A1->y, A3->y);
        gbox->xmax = FP_MAX(A1->x, A3->x);
        gbox->ymax = FP_MAX(A1->y, A3->y);
            return LW_SUCCESS;
        }

        /* Matched start/end points imply circle */
        if ( A1->x == A3->x && A1->y == A3->y )
        {
                gbox->xmin = C.x - radius_A;
                gbox->ymin = C.y - radius_A;
                gbox->xmax = C.x + radius_A;
                gbox->ymax = C.y + radius_A;
                return LW_SUCCESS;
        }

        /* First approximation, bounds of start/end points */
    gbox->xmin = FP_MIN(A1->x, A3->x);
    gbox->ymin = FP_MIN(A1->y, A3->y);
    gbox->xmax = FP_MAX(A1->x, A3->x);
    gbox->ymax = FP_MAX(A1->y, A3->y);

        /* Create points for the possible extrema */
        xmin.x = C.x - radius_A;
        xmin.y = C.y;
        ymin.x = C.x;
        ymin.y = C.y - radius_A;
        xmax.x = C.x + radius_A;
        xmax.y = C.y;
        ymax.x = C.x;
        ymax.y = C.y + radius_A;

        /* Divide the circle into two parts, one on each side of a line
           joining p1 and p3. The circle extrema on the same side of that line
           as p2 is on, are also the extrema of the bbox. */

        A2_side = lw_segment_side(A1, A3, A2);

        if ( A2_side == lw_segment_side(A1, A3, &xmin) )
                gbox->xmin = xmin.x;

        if ( A2_side == lw_segment_side(A1, A3, &ymin) )
                gbox->ymin = ymin.y;

        if ( A2_side == lw_segment_side(A1, A3, &xmax) )
                gbox->xmax = xmax.x;

        if ( A2_side == lw_segment_side(A1, A3, &ymax) )
                gbox->ymax = ymax.y;

        return LW_SUCCESS;
}

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