Function readCodewords

src/decoder/decoder.ts:102–140

(matrix: BitMatrix, version: Version, formatInfo: FormatInformation)

}

function readCodewords(matrix: BitMatrix, version: Version, formatInfo: FormatInformation) {
  const dataMask = DATA_MASKS[formatInfo.dataMask];
  const dimension = matrix.height;

  const functionPatternMask = buildFunctionPatternMask(version);

  const codewords: number[] = [];
  let currentByte = 0;
  let bitsRead = 0;

  // Read columns in pairs, from right to left
  let readingUp = true;
  for (let columnIndex = dimension - 1; columnIndex > 0; columnIndex -= 2) {
    if (columnIndex === 6) { // Skip whole column with vertical alignment pattern;
      columnIndex--;
    }
    for (let i = 0; i < dimension; i++) {
      const y = readingUp ? dimension - 1 - i : i;
      for (let columnOffset = 0; columnOffset < 2; columnOffset++) {
        const x = columnIndex - columnOffset;
        if (!functionPatternMask.get(x, y)) {
          bitsRead++;
          let bit = matrix.get(x, y);
          if (dataMask({y, x})) {
            bit = !bit;
          }
          currentByte = pushBit(bit, currentByte);
          if (bitsRead === 8) { // Whole bytes
            codewords.push(currentByte);
            bitsRead = 0;
            currentByte = 0;
          }
        }
      }
    }
    readingUp = !readingUp;
  }
  return codewords;
}

function readVersion(matrix: BitMatrix): Version {
  const dimension = matrix.height;