lwtriangle_area()

double lwtriangle_area

(

const LWTRIANGLE *

triangle

)

Find the area of the outer ring.

Definition at line 192 of file lwtriangle.c.

References area(), getPoint2d_p(), POINTARRAY::npoints, rect_node::p1, rect_node::p2, LWTRIANGLE::points, POINT2D::x, and POINT2D::y.

Referenced by lwgeom_area().

{
        double area=0.0;
        int i;
        POINT2D p1;
        POINT2D p2;

        if (! triangle->points->npoints) return area; /* empty triangle */

        for (i=0; i < triangle->points->npoints-1; i++)
        {
                getPoint2d_p(triangle->points, i, &p1);
                getPoint2d_p(triangle->points, i+1, &p2);
                area += ( p1.x * p2.y ) - ( p1.y * p2.x );
        }

        area  /= 2.0;

        return fabs(area);
}

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