image-js/lib/featureMatching/keypoints/getHarrisScore.js

Image processing and manipulation in JavaScript

import { getEigenvaluesForScore } from './getEigenvaluesForScore.js';
/**
 * Get the Harris score of a corner. The idea behind the algorithm is that a
 * slight shift of a window around a corner along x and y should result in
 * a very different image.
 *
 * We distinguish 3 cases:
 * - the score is highly negative: you have an edge
 * - the absolute value of the score is small: the region is flat
 * - the score is highly positive: you have a corner.
 * @see {@link https://en.wikipedia.org/wiki/Harris_corner_detector}
 * @param image - Image to which the corner belongs. It must be a greyscale image with only one channel.
 * @param origin - Center of the window, where the corner should be.
 * @param options - Get Harris score options.
 * @returns The Harris score.
 */
export function getHarrisScore(image, origin, options = {}) {
    const { harrisConstant = 0.04, windowSize } = options;
    const eigenValues = getEigenvaluesForScore(image, origin, windowSize);
    return (eigenValues[0] * eigenValues[1] -
        harrisConstant * (eigenValues[0] + eigenValues[1]) ** 2);
}
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