lwpoly_area()

double lwpoly_area

(

const LWPOLY *

poly

)

Find the area of the outer ring - sum (area of inner rings).

Definition at line 524 of file lwpoly.c.

References lwerror(), POINTARRAY::npoints, LWPOLY::nrings, ptarray_signed_area(), and LWPOLY::rings.

Referenced by lwcurvepoly_area(), lwgeom_area(), lwmpoly_to_points(), and lwpoly_to_points().

{
        double poly_area = 0.0;
        int i;

        if ( ! poly )
                lwerror("lwpoly_area called with null polygon pointer!");

        for ( i=0; i < poly->nrings; i++ )
        {
                POINTARRAY *ring = poly->rings[i];
                double ringarea = 0.0;

                /* Empty or messed-up ring. */
                if ( ring->npoints < 3 )
                        continue;

                ringarea = fabs(ptarray_signed_area(ring));
                if ( i == 0 ) /* Outer ring, positive area! */
                        poly_area += ringarea;
                else /* Inner ring, negative area! */
                        poly_area -= ringarea;
        }

        return poly_area;
}

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