image-js/src/featureMatching/keypoints/getIntensityMoment.ts

Image processing and manipulation in JavaScript

import type { Image } from '../../Image.js';
import type { Point } from '../../geometry/index.js';

export interface GetIntensityMomentOptions {
  /**
   * Origin for the moment computation.
   * @default `image.getCoordinates('center')`.
   */
  origin?: Point;
}

/**
 * Compute the pq order intensity moment of the image
 * relatively to the origin defined in the options.
 * Original article: {@link https://doi.org/10.1006/cviu.1998.0719}.
 * @see {@link https://en.wikipedia.org/wiki/Image_moment}
 * @param image - Image to process. Should have an odd number of rows and columns.
 * @param p - Order along x.
 * @param q - Order along y.
 * @param options - Get intensity moment options.
 * @returns The intensity moment of order pq.
 */
export function getIntensityMoment(
  image: Image,
  p: number,
  q: number,
  options: GetIntensityMomentOptions = {},
): number[] {
  const { origin = image.getCoordinates('center') } = options;

  const moment = new Array<number>(image.channels).fill(0);
  for (let row = 0; row < image.height; row++) {
    for (let column = 0; column < image.width; column++) {
      const xDistance = column - origin.column;
      const yDistance = row - origin.row;
      for (let channel = 0; channel < image.channels; channel++) {
        const intensity = image.getValue(column, row, channel);
        moment[channel] += xDistance ** p * yDistance ** q * intensity;
      }
    }
  }
  return moment;
}