/*
 * cvhharea.c		Jim Piper	11-09-86
 *
 * Compute area under "convex semi-hull of histogram" object
 * (which is in fact an open polygon).  To make this area more
 * nearly comparable with the histogram integral, notional zero-height points
 * one unit to the left and right of the convex hull are assumed.
 */

#include <stdio.h>
#include <wstruct.h>


cvhharea (cvhh)
struct object *cvhh;
{
	register int i,cvhhar;
	register struct polygondomain *cvhpdom;
	register struct ivertex *vtx, *wtx;

	cvhpdom = (struct polygondomain *) cvhh->idom;
	vtx = cvhpdom->vtx;
	wtx = vtx+1;
	cvhhar = vtx->vtY;
	for (i=1; i<cvhpdom->nvertices; i++,vtx++,wtx++)
		cvhhar += (wtx->vtX-vtx->vtX) * (wtx->vtY+vtx->vtY);
	cvhhar += vtx->vtY;
	return(cvhhar/2);
}