Function readVersion

src/decoder/decoder.ts:142–188

(matrix: BitMatrix)

}

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

  const provisionalVersion = Math.floor((dimension - 17) / 4);
  if (provisionalVersion <= 6) { // 6 and under dont have version info in the QR code
    return VERSIONS[provisionalVersion - 1];
  }

  let topRightVersionBits = 0;
  for (let y = 5; y >= 0; y--) {
    for (let x = dimension - 9; x >= dimension - 11; x--) {
      topRightVersionBits = pushBit(matrix.get(x, y), topRightVersionBits);
    }
  }

  let bottomLeftVersionBits = 0;
  for (let x = 5; x >= 0; x--) {
    for (let y = dimension - 9; y >= dimension - 11; y--) {
      bottomLeftVersionBits = pushBit(matrix.get(x, y), bottomLeftVersionBits);
    }
  }

  let bestDifference = Infinity;
  let bestVersion: Version;
  for (const version of VERSIONS) {
    if (version.infoBits === topRightVersionBits || version.infoBits === bottomLeftVersionBits) {
      return version;
    }

    let difference = numBitsDiffering(topRightVersionBits, version.infoBits);
    if (difference < bestDifference) {
      bestVersion = version;
      bestDifference = difference;
    }

    difference = numBitsDiffering(bottomLeftVersionBits, version.infoBits);
    if (difference < bestDifference) {
      bestVersion = version;
      bestDifference = difference;
    }
  }
  // We can tolerate up to 3 bits of error since no two version info codewords will
  // differ in less than 8 bits.
  if (bestDifference <= 3) {
    return bestVersion;
  }
}

function readFormatInformation(matrix: BitMatrix) {
  let topLeftFormatInfoBits = 0;