All files / packages/tools/src/utilities/math/polyline calculateAreaOfPoints.ts

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import type { Types } from '@cornerstonejs/core';
 
/**
 * Calculates the area of an array of `Point2` points using the shoelace algorithm.
 *
 * The units of the area are in the same units as the points are in. E.g. if
 * the points are in canvas, then the result is in canvas pixels ^2; If they are
 * in mm, then the result is in mm^2; etc.
 */
export default function calculateAreaOfPoints(points: Types.Point2[]): number {
  // Shoelace algorithm.
  const n = points.length;
  let area = 0.0;
  let j = n - 1;
 
  for (let i = 0; i < n; i++) {
    area += (points[j][0] + points[i][0]) * (points[j][1] - points[i][1]);
    j = i; // j is previous vertex to i
  }
 
  // Return absolute value of half the sum (half as summing up traingles).
  return Math.abs(area / 2.0);
}