@zxing/library
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TypeScript port of ZXing multi-format 1D/2D barcode image processing library.
160 lines (159 loc) • 7.1 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.
*/
/*namespace com.google.zxing.qrcode.decoder {*/
import ChecksumException from '../../ChecksumException';
import BitMatrix from '../../common/BitMatrix';
import GenericGF from '../../common/reedsolomon/GenericGF';
import ReedSolomonDecoder from '../../common/reedsolomon/ReedSolomonDecoder';
import BitMatrixParser from './BitMatrixParser';
import DataBlock from './DataBlock';
import DecodedBitStreamParser from './DecodedBitStreamParser';
import QRCodeDecoderMetaData from './QRCodeDecoderMetaData';
/*import java.util.Map;*/
/**
* <p>The main class which implements QR Code decoding -- as opposed to locating and extracting
* the QR Code from an image.</p>
*
* @author Sean Owen
*/
export default class Decoder {
constructor() {
this.rsDecoder = new ReedSolomonDecoder(GenericGF.QR_CODE_FIELD_256);
}
// public decode(image: boolean[][]): DecoderResult /*throws ChecksumException, FormatException*/ {
// return decode(image, null)
// }
/**
* <p>Convenience method that can decode a QR Code represented as a 2D array of booleans.
* "true" is taken to mean a black module.</p>
*
* @param image booleans representing white/black QR Code modules
* @param hints decoding hints that should be used to influence decoding
* @return text and bytes encoded within the QR Code
* @throws FormatException if the QR Code cannot be decoded
* @throws ChecksumException if error correction fails
*/
decodeBooleanArray(image, hints) {
return this.decodeBitMatrix(BitMatrix.parseFromBooleanArray(image), hints);
}
// public decodeBitMatrix(bits: BitMatrix): DecoderResult /*throws ChecksumException, FormatException*/ {
// return decode(bits, null)
// }
/**
* <p>Decodes a QR Code represented as a {@link BitMatrix}. A 1 or "true" is taken to mean a black module.</p>
*
* @param bits booleans representing white/black QR Code modules
* @param hints decoding hints that should be used to influence decoding
* @return text and bytes encoded within the QR Code
* @throws FormatException if the QR Code cannot be decoded
* @throws ChecksumException if error correction fails
*/
decodeBitMatrix(bits, hints) {
// Construct a parser and read version, error-correction level
const parser = new BitMatrixParser(bits);
let ex = null;
try {
return this.decodeBitMatrixParser(parser, hints);
}
catch (e /*: FormatException, ChecksumException*/) {
ex = e;
}
try {
// Revert the bit matrix
parser.remask();
// Will be attempting a mirrored reading of the version and format info.
parser.setMirror(true);
// Preemptively read the version.
parser.readVersion();
// Preemptively read the format information.
parser.readFormatInformation();
/*
* Since we're here, this means we have successfully detected some kind
* of version and format information when mirrored. This is a good sign,
* that the QR code may be mirrored, and we should try once more with a
* mirrored content.
*/
// Prepare for a mirrored reading.
parser.mirror();
const result = this.decodeBitMatrixParser(parser, hints);
// Success! Notify the caller that the code was mirrored.
result.setOther(new QRCodeDecoderMetaData(true));
return result;
}
catch (e /*FormatException | ChecksumException*/) {
// Throw the exception from the original reading
if (ex !== null) {
throw ex;
}
throw e;
}
}
decodeBitMatrixParser(parser, hints) {
const version = parser.readVersion();
const ecLevel = parser.readFormatInformation().getErrorCorrectionLevel();
// Read codewords
const codewords = parser.readCodewords();
// Separate into data blocks
const dataBlocks = DataBlock.getDataBlocks(codewords, version, ecLevel);
// Count total number of data bytes
let totalBytes = 0;
for (const dataBlock of dataBlocks) {
totalBytes += dataBlock.getNumDataCodewords();
}
const resultBytes = new Uint8Array(totalBytes);
let resultOffset = 0;
// Error-correct and copy data blocks together into a stream of bytes
for (const dataBlock of dataBlocks) {
const codewordBytes = dataBlock.getCodewords();
const numDataCodewords = dataBlock.getNumDataCodewords();
this.correctErrors(codewordBytes, numDataCodewords);
for (let i = 0; i < numDataCodewords; i++) {
resultBytes[resultOffset++] = codewordBytes[i];
}
}
// Decode the contents of that stream of bytes
return DecodedBitStreamParser.decode(resultBytes, version, ecLevel, hints);
}
/**
* <p>Given data and error-correction codewords received, possibly corrupted by errors, attempts to
* correct the errors in-place using Reed-Solomon error correction.</p>
*
* @param codewordBytes data and error correction codewords
* @param numDataCodewords number of codewords that are data bytes
* @throws ChecksumException if error correction fails
*/
correctErrors(codewordBytes, numDataCodewords /*int*/) {
// const numCodewords = codewordBytes.length;
// First read into an array of ints
const codewordsInts = new Int32Array(codewordBytes);
// TYPESCRIPTPORT: not realy necessary to transform to ints? could redesign everything to work with unsigned bytes?
// const codewordsInts = new Int32Array(numCodewords)
// for (let i = 0; i < numCodewords; i++) {
// codewordsInts[i] = codewordBytes[i] & 0xFF
// }
try {
this.rsDecoder.decode(codewordsInts, codewordBytes.length - numDataCodewords);
}
catch (ignored /*: ReedSolomonException*/) {
throw new ChecksumException();
}
// Copy back into array of bytes -- only need to worry about the bytes that were data
// We don't care about errors in the error-correction codewords
for (let i = 0; i < numDataCodewords; i++) {
codewordBytes[i] = /*(byte) */ codewordsInts[i];
}
}
}