@nuintun/qrcode/esm/detector/PatternFinder.js

A pure JavaScript QRCode encode and decode library.

/**
 * @module QRCode
 * @package @nuintun/qrcode
 * @license MIT
 * @version 5.0.2
 * @author nuintun <nuintun@qq.com>
 * @description A pure JavaScript QRCode encode and decode library.
 * @see https://github.com/nuintun/qrcode#readme
 */

import { Pattern } from './Pattern.js';
import { accumulate } from '../common/utils.js';
import { centerFromScanlineEnd, getDiagonalScanline } from './utils/scanline.js';
import { alignCrossPattern, isDiagonalScanlineCheckPassed, calculatePatternNoise } from './utils/pattern.js';

/**
 * @module PatternFinder
 */
class PatternFinder {
  #strict;
  #matrix;
  #ratios;
  #patterns = [];
  constructor(matrix, ratios, strict) {
    this.#matrix = matrix;
    this.#ratios = ratios;
    this.#strict = strict;
  }
  get matrix() {
    return this.#matrix;
  }
  get patterns() {
    return this.#patterns;
  }
  match(x, y, scanline, overscan) {
    const matrix = this.#matrix;
    const ratios = this.#ratios;
    let centerX = centerFromScanlineEnd(scanline, x);
    const [centerY, vertical] = alignCrossPattern(matrix, centerX, y, overscan, ratios, true);
    if (centerY >= 0) {
      let horizontal;
      // Re-horizontal check.
      [centerX, horizontal] = alignCrossPattern(matrix, centerX, centerY, overscan, ratios);
      if (centerX >= 0) {
        const slash = getDiagonalScanline(matrix, centerX, centerY, overscan);
        const backslash = getDiagonalScanline(matrix, centerX, centerY, overscan, true);
        if (isDiagonalScanlineCheckPassed(slash, backslash, ratios, this.#strict)) {
          const noise = calculatePatternNoise(ratios, horizontal, vertical, slash, backslash);
          const width = accumulate(horizontal);
          const height = accumulate(vertical);
          const patterns = this.#patterns;
          const { length } = patterns;
          let combined = false;
          for (let i = 0; i < length; i++) {
            const pattern = patterns[i];
            // Look for about the same center and module size.
            if (Pattern.equals(pattern, centerX, centerY, width, height)) {
              combined = true;
              patterns[i] = Pattern.combine(pattern, centerX, centerY, width, height, noise);
              break;
            }
          }
          // Hadn't found this before; save it.
          if (!combined) {
            patterns.push(new Pattern(ratios, centerX, centerY, width, height, noise));
          }
        }
      }
    }
  }
}

export { PatternFinder };