/* * 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. */ package com.google.zxing.qrcode.decoder; import java.util.Map; import com.google.zxing.ChecksumException; import com.google.zxing.DecodeHintType; import com.google.zxing.FormatException; import com.google.zxing.common.BitMatrix; import com.google.zxing.common.DecoderResult; import com.google.zxing.common.reedsolomon.GenericGF; import com.google.zxing.common.reedsolomon.ReedSolomonDecoder; import com.google.zxing.common.reedsolomon.ReedSolomonException; /** *
The main class which implements QR Code decoding -- as opposed to locating and extracting * the QR Code from an image.
* * @author Sean Owen */ public final class Decoder { private final ReedSolomonDecoder rsDecoder; public Decoder() { rsDecoder = new ReedSolomonDecoder(GenericGF.QR_CODE_FIELD_256); } public DecoderResult decode(boolean[][] image) throws ChecksumException, FormatException { return decode(image, null); } /** *Convenience method that can decode a QR Code represented as a 2D array of booleans. * "true" is taken to mean a black module.
* * @param image booleans representing white/black QR Code modules * @return text and bytes encoded within the QR Code * @throws FormatException if the QR Code cannot be decoded * @throws ChecksumException if error correction fails */ public DecoderResult decode(boolean[][] image, MapDecodes a QR Code represented as a {@link BitMatrix}. A 1 or "true" is taken to mean a black module.
* * @param bits booleans representing white/black QR Code modules * @return text and bytes encoded within the QR Code * @throws FormatException if the QR Code cannot be decoded * @throws ChecksumException if error correction fails */ public DecoderResult decode(BitMatrix bits, MapGiven data and error-correction codewords received, possibly corrupted by errors, attempts to * correct the errors in-place using Reed-Solomon error correction.
* * @param codewordBytes data and error correction codewords * @param numDataCodewords number of codewords that are data bytes * @throws ChecksumException if error correction fails */ private void correctErrors(byte[] codewordBytes, int numDataCodewords) throws ChecksumException { int numCodewords = codewordBytes.length; // First read into an array of ints int[] codewordsInts = new int[numCodewords]; for (int i = 0; i < numCodewords; i++) { codewordsInts[i] = codewordBytes[i] & 0xFF; } int numECCodewords = codewordBytes.length - numDataCodewords; try { rsDecoder.decode(codewordsInts, numECCodewords); } catch (ReedSolomonException ignored) { throw ChecksumException.getChecksumInstance(); } // 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 (int i = 0; i < numDataCodewords; i++) { codewordBytes[i] = (byte) codewordsInts[i]; } } }