@zxing/library
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TypeScript port of ZXing multi-format 1D/2D barcode image processing library.
216 lines (215 loc) • 9.18 kB
JavaScript
/*
* 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.
*/
import Version from './Version';
import FormatInformation from './FormatInformation';
import DataMask from './DataMask';
import FormatException from '../../FormatException';
/**
* @author Sean Owen
*/
export default class BitMatrixParser {
/**
* @param bitMatrix {@link BitMatrix} to parse
* @throws FormatException if dimension is not >= 21 and 1 mod 4
*/
constructor(bitMatrix) {
const dimension = bitMatrix.getHeight();
if (dimension < 21 || (dimension & 0x03) !== 1) {
throw new FormatException();
}
this.bitMatrix = bitMatrix;
}
/**
* <p>Reads format information from one of its two locations within the QR Code.</p>
*
* @return {@link FormatInformation} encapsulating the QR Code's format info
* @throws FormatException if both format information locations cannot be parsed as
* the valid encoding of format information
*/
readFormatInformation() {
if (this.parsedFormatInfo !== null && this.parsedFormatInfo !== undefined) {
return this.parsedFormatInfo;
}
// Read top-left format info bits
let formatInfoBits1 = 0;
for (let i = 0; i < 6; i++) {
formatInfoBits1 = this.copyBit(i, 8, formatInfoBits1);
}
// .. and skip a bit in the timing pattern ...
formatInfoBits1 = this.copyBit(7, 8, formatInfoBits1);
formatInfoBits1 = this.copyBit(8, 8, formatInfoBits1);
formatInfoBits1 = this.copyBit(8, 7, formatInfoBits1);
// .. and skip a bit in the timing pattern ...
for (let j = 5; j >= 0; j--) {
formatInfoBits1 = this.copyBit(8, j, formatInfoBits1);
}
// Read the top-right/bottom-left pattern too
const dimension = this.bitMatrix.getHeight();
let formatInfoBits2 = 0;
const jMin = dimension - 7;
for (let j = dimension - 1; j >= jMin; j--) {
formatInfoBits2 = this.copyBit(8, j, formatInfoBits2);
}
for (let i = dimension - 8; i < dimension; i++) {
formatInfoBits2 = this.copyBit(i, 8, formatInfoBits2);
}
this.parsedFormatInfo = FormatInformation.decodeFormatInformation(formatInfoBits1, formatInfoBits2);
if (this.parsedFormatInfo !== null) {
return this.parsedFormatInfo;
}
throw new FormatException();
}
/**
* <p>Reads version information from one of its two locations within the QR Code.</p>
*
* @return {@link Version} encapsulating the QR Code's version
* @throws FormatException if both version information locations cannot be parsed as
* the valid encoding of version information
*/
readVersion() {
if (this.parsedVersion !== null && this.parsedVersion !== undefined) {
return this.parsedVersion;
}
const dimension = this.bitMatrix.getHeight();
const provisionalVersion = Math.floor((dimension - 17) / 4);
if (provisionalVersion <= 6) {
return Version.getVersionForNumber(provisionalVersion);
}
// Read top-right version info: 3 wide by 6 tall
let versionBits = 0;
const ijMin = dimension - 11;
for (let j = 5; j >= 0; j--) {
for (let i = dimension - 9; i >= ijMin; i--) {
versionBits = this.copyBit(i, j, versionBits);
}
}
let theParsedVersion = Version.decodeVersionInformation(versionBits);
if (theParsedVersion !== null && theParsedVersion.getDimensionForVersion() === dimension) {
this.parsedVersion = theParsedVersion;
return theParsedVersion;
}
// Hmm, failed. Try bottom left: 6 wide by 3 tall
versionBits = 0;
for (let i = 5; i >= 0; i--) {
for (let j = dimension - 9; j >= ijMin; j--) {
versionBits = this.copyBit(i, j, versionBits);
}
}
theParsedVersion = Version.decodeVersionInformation(versionBits);
if (theParsedVersion !== null && theParsedVersion.getDimensionForVersion() === dimension) {
this.parsedVersion = theParsedVersion;
return theParsedVersion;
}
throw new FormatException();
}
copyBit(i /*int*/, j /*int*/, versionBits /*int*/) {
const bit = this.isMirror ? this.bitMatrix.get(j, i) : this.bitMatrix.get(i, j);
return bit ? (versionBits << 1) | 0x1 : versionBits << 1;
}
/**
* <p>Reads the bits in the {@link BitMatrix} representing the finder pattern in the
* correct order in order to reconstruct the codewords bytes contained within the
* QR Code.</p>
*
* @return bytes encoded within the QR Code
* @throws FormatException if the exact number of bytes expected is not read
*/
readCodewords() {
const formatInfo = this.readFormatInformation();
const version = this.readVersion();
// Get the data mask for the format used in this QR Code. This will exclude
// some bits from reading as we wind through the bit matrix.
const dataMask = DataMask.values.get(formatInfo.getDataMask());
const dimension = this.bitMatrix.getHeight();
dataMask.unmaskBitMatrix(this.bitMatrix, dimension);
const functionPattern = version.buildFunctionPattern();
let readingUp = true;
const result = new Uint8Array(version.getTotalCodewords());
let resultOffset = 0;
let currentByte = 0;
let bitsRead = 0;
// Read columns in pairs, from right to left
for (let j = dimension - 1; j > 0; j -= 2) {
if (j === 6) {
// Skip whole column with vertical alignment pattern
// saves time and makes the other code proceed more cleanly
j--;
}
// Read alternatingly from bottom to top then top to bottom
for (let count = 0; count < dimension; count++) {
const i = readingUp ? dimension - 1 - count : count;
for (let col = 0; col < 2; col++) {
// Ignore bits covered by the function pattern
if (!functionPattern.get(j - col, i)) {
// Read a bit
bitsRead++;
currentByte <<= 1;
if (this.bitMatrix.get(j - col, i)) {
currentByte |= 1;
}
// If we've made a whole byte, save it off
if (bitsRead === 8) {
result[resultOffset++] = /*(byte) */ currentByte;
bitsRead = 0;
currentByte = 0;
}
}
}
}
readingUp = !readingUp; // readingUp ^= true; // readingUp = !readingUp; // switch directions
}
if (resultOffset !== version.getTotalCodewords()) {
throw new FormatException();
}
return result;
}
/**
* Revert the mask removal done while reading the code words. The bit matrix should revert to its original state.
*/
remask() {
if (this.parsedFormatInfo === null) {
return; // We have no format information, and have no data mask
}
const dataMask = DataMask.values.get(this.parsedFormatInfo.getDataMask());
const dimension = this.bitMatrix.getHeight();
dataMask.unmaskBitMatrix(this.bitMatrix, dimension);
}
/**
* Prepare the parser for a mirrored operation.
* This flag has effect only on the {@link #readFormatInformation()} and the
* {@link #readVersion()}. Before proceeding with {@link #readCodewords()} the
* {@link #mirror()} method should be called.
*
* @param mirror Whether to read version and format information mirrored.
*/
setMirror(isMirror) {
this.parsedVersion = null;
this.parsedFormatInfo = null;
this.isMirror = isMirror;
}
/** Mirror the bit matrix in order to attempt a second reading. */
mirror() {
const bitMatrix = this.bitMatrix;
for (let x = 0, width = bitMatrix.getWidth(); x < width; x++) {
for (let y = x + 1, height = bitMatrix.getHeight(); y < height; y++) {
if (bitMatrix.get(x, y) !== bitMatrix.get(y, x)) {
bitMatrix.flip(y, x);
bitMatrix.flip(x, y);
}
}
}
}
}