image-js/lib/featureMatching/descriptors/utils/getKeypointPatch.js

Image processing and manipulation in JavaScript

import { getRadius } from '../../../utils/getRadius.js';
import { checkBorderDistance } from '../../utils/checkBorderDistance.js';
import { extractSquareImage } from '../../utils/extractSquareImage.js';
/**
 * Get the patch around the keypoint with given size.
 * @param image - Image from which to extract the patch.
 * @param keypoint - Keypoint around which to extract the patch.
 * @param options - Get keypoint patch options.
 * @returns The patch around the keypoint.
 */
export function getKeypointPatch(image, keypoint, options = {}) {
    const { patchSize = 31 } = options;
    // crop smallest square surrounding the tilted patch of the keypoint
    // we have to handle the fact that this square can have even dimensions
    const radAngle = (keypoint.angle * Math.PI) / 180;
    const rawWidth = Math.floor(patchSize * (Math.abs(Math.cos(radAngle)) + Math.abs(Math.sin(radAngle))));
    const cropWidth = rawWidth % 2 ? rawWidth : rawWidth + 1;
    // we are not allowing keypoints that are too close to the border of the image
    const borderDistance = getRadius(cropWidth);
    if (!checkBorderDistance(image, keypoint.origin, borderDistance)) {
        throw new RangeError('keypoint is too close to border for given patch size');
    }
    const cropped = extractSquareImage(image, keypoint.origin, cropWidth);
    const rotated = cropped.transformRotate(-keypoint.angle, {
        center: 'center',
        interpolationType: 'nearest',
    });
    const cropOrigin = rotated.getCoordinates('center');
    const result = extractSquareImage(rotated, cropOrigin, patchSize);
    return result;
}
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