Class MaxiCodeReader

src/core/maxicode/MaxiCodeReader.ts:32–94

 * This implementation can detect and decode a MaxiCode in an image.
 */
export default class MaxiCodeReader implements Reader {

  private static readonly NO_POINTS: ResultPoint[] = [];
  private static readonly MATRIX_WIDTH = 30;
  private static readonly MATRIX_HEIGHT = 33;

  private decoder: Decoder = new Decoder();

  public decode(image: BinaryBitmap, hints: Map<DecodeHintType, any> | null = null): Result {
    // Note that MaxiCode reader effectively always assumes PURE_BARCODE mode
    // and can't detect it in an image
    const bits = MaxiCodeReader.extractPureBits(image.getBlackMatrix());
    const decoderResult = this.decoder.decode(bits, hints);
    const result = new Result(
      decoderResult.getText(),
      decoderResult.getRawBytes(),
      8 * decoderResult.getRawBytes().length,
      MaxiCodeReader.NO_POINTS,
      BarcodeFormat.MAXICODE,
      System.currentTimeMillis()
    );
    result.putMetadata(ResultMetadataType.ERRORS_CORRECTED, decoderResult.getErrorsCorrected());
    const ecLevel = decoderResult.getECLevel();
    if (ecLevel != null) {
      result.putMetadata(ResultMetadataType.ERROR_CORRECTION_LEVEL, ecLevel);
    }
    return result;
  }

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

  private static extractPureBits(image: BitMatrix): BitMatrix {
    const enclosingRectangle = image.getEnclosingRectangle();
    if (enclosingRectangle == null) {
      throw new NotFoundException();
    }

    const left = enclosingRectangle[0];
    const top = enclosingRectangle[1];
    const width = enclosingRectangle[2];
    const height = enclosingRectangle[3];

    // Now just read off the bits
    const bits = new BitMatrix(MaxiCodeReader.MATRIX_WIDTH, MaxiCodeReader.MATRIX_HEIGHT);
    for (let y = 0; y < MaxiCodeReader.MATRIX_HEIGHT; y++) {
      const iy = top + Math.min(Math.floor((y * height + height / 2) / MaxiCodeReader.MATRIX_HEIGHT), height - 1);
      for (let x = 0; x < MaxiCodeReader.MATRIX_WIDTH; x++) {
        // srowen: I don't quite understand why the formula below is necessary, but it
        // can walk off the image if left + width = the right boundary. So cap it.
        const ix = left + Math.min(
          Math.floor((x * width + width / 2 + (y & 0x01) * Math.floor(width / 2)) / MaxiCodeReader.MATRIX_WIDTH),
          width - 1);
        if (image.get(ix, iy)) {
          bits.set(x, y);
        }
      }