zxing-js/library

import BarcodeFormat from '../BarcodeFormat';
import BinaryBitmap from '../BinaryBitmap';
import BitMatrix from '../common/BitMatrix';
import DecoderResult from '../common/DecoderResult';
import DecodeHintType from '../DecodeHintType';
import NotFoundException from '../NotFoundException';
import Reader from '../Reader';
import Result from '../Result';
import ResultMetadataType from '../ResultMetadataType';
import ResultPoint from '../ResultPoint';
import System from '../util/System';
import Decoder from './decoder/Decoder';
import Detector from './detector/Detector';


/*
 * Copyright 2007 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * This implementation can detect and decode Data Matrix codes in an image.
 *
 * @author bbrown@google.com (Brian Brown)
 */
export default class DataMatrixReader implements Reader {

  private static NO_POINTS: ResultPoint[] = [];

  private decoder: Decoder = new Decoder();

  /**
   * Locates and decodes a Data Matrix code in an image.
   *
   * @return a String representing the content encoded by the Data Matrix code
   * @throws NotFoundException if a Data Matrix code cannot be found
   * @throws FormatException if a Data Matrix code cannot be decoded
   * @throws ChecksumException if error correction fails
   */
  // @Override
  // public Result decode(BinaryBitmap image) throws NotFoundException, ChecksumException, FormatException {
  //   return decode(image, null);
  // }

  // @Override
  public decode(image: BinaryBitmap, hints: Map<DecodeHintType, any> | null = null): Result {
    let decoderResult: DecoderResult;
    let points: ResultPoint[];

    if (hints != null && hints.has(DecodeHintType.PURE_BARCODE)) {
      const bits = DataMatrixReader.extractPureBits(image.getBlackMatrix());
      decoderResult = this.decoder.decode(bits);
      points = DataMatrixReader.NO_POINTS;
    } else {
      const detectorResult = new Detector(image.getBlackMatrix()).detect();
      decoderResult = this.decoder.decode(detectorResult.getBits());
      points = detectorResult.getPoints();
    }
    const rawBytes = decoderResult.getRawBytes();
    const result = new Result(
      decoderResult.getText(),
      rawBytes,
      8 * rawBytes.length,
      points,
      BarcodeFormat.DATA_MATRIX,
      System.currentTimeMillis()
    );

    const byteSegments = decoderResult.getByteSegments();
    if (byteSegments != null) {
      result.putMetadata(ResultMetadataType.BYTE_SEGMENTS, byteSegments);
    }
    const ecLevel = decoderResult.getECLevel();
    if (ecLevel != null) {
      result.putMetadata(ResultMetadataType.ERROR_CORRECTION_LEVEL, ecLevel);
    }
    return result;
  }

  // @Override
  public reset(): void {
    // do nothing
  }

  /**
   * This method detects a code in a "pure" image -- that is, pure monochrome image
   * which contains only an unrotated, unskewed, image of a code, with some white border
   * around it. This is a specialized method that works exceptionally fast in this special
   * case.
   *
   * @see com.google.zxing.qrcode.QRCodeReader#extractPureBits(BitMatrix)
   */
  private static extractPureBits(image: BitMatrix): BitMatrix {

    const leftTopBlack = image.getTopLeftOnBit();
    const rightBottomBlack = image.getBottomRightOnBit();
    if (leftTopBlack == null || rightBottomBlack == null) {
      throw new NotFoundException();
    }

    const moduleSize = this.moduleSize(leftTopBlack, image);

    let top = leftTopBlack[1];
    const bottom = rightBottomBlack[1];
    let left = leftTopBlack[0];
    const right = rightBottomBlack[0];

    const matrixWidth = (right - left + 1) / moduleSize;
    const matrixHeight = (bottom - top + 1) / moduleSize;
    if (matrixWidth <= 0 || matrixHeight <= 0) {
      throw new NotFoundException();
    }

    // Push in the "border" by half the module width so that we start
    // sampling in the middle of the module. Just in case the image is a
    // little off, this will help recover.
    const nudge = moduleSize / 2;
    top += nudge;
    left += nudge;

    // Now just read off the bits
    const bits = new BitMatrix(matrixWidth, matrixHeight);
    for (let y = 0; y < matrixHeight; y++) {
      const iOffset = top + y * moduleSize;
      for (let x = 0; x < matrixWidth; x++) {
        if (image.get(left + x * moduleSize, iOffset)) {
          bits.set(x, y);
        }
      }
    }
    return bits;
  }

  private static moduleSize(leftTopBlack: Int32Array, image: BitMatrix): number {
    const width = image.getWidth();
    let x = leftTopBlack[0];
    const y = leftTopBlack[1];
    while (x < width && image.get(x, y)) {
      x++;
    }
    if (x === width) {
      throw new NotFoundException();
    }

    const moduleSize = x - leftTopBlack[0];
    if (moduleSize === 0) {
      throw new NotFoundException();
    }
    return moduleSize;
  }

}