203 lines
6.9 KiB
Java
203 lines
6.9 KiB
Java
/*
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* Copyright 2007 ZXing authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.zxing.qrcode.decoder;
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import com.google.zxing.FormatException;
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import com.google.zxing.common.BitMatrix;
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/**
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* @author Sean Owen
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*/
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final class BitMatrixParser {
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private final BitMatrix bitMatrix;
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private Version parsedVersion;
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private FormatInformation parsedFormatInfo;
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/**
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* @param bitMatrix {@link BitMatrix} to parse
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* @throws FormatException if dimension is not >= 21 and 1 mod 4
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*/
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BitMatrixParser(BitMatrix bitMatrix) throws FormatException {
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int dimension = bitMatrix.getHeight();
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if (dimension < 21 || (dimension & 0x03) != 1) {
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throw FormatException.getFormatInstance();
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}
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this.bitMatrix = bitMatrix;
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}
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/**
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* <p>Reads format information from one of its two locations within the QR Code.</p>
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*
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* @return {@link FormatInformation} encapsulating the QR Code's format info
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* @throws FormatException if both format information locations cannot be parsed as
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* the valid encoding of format information
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*/
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FormatInformation readFormatInformation() throws FormatException {
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if (parsedFormatInfo != null) {
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return parsedFormatInfo;
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}
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// Read top-left format info bits
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int formatInfoBits1 = 0;
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for (int i = 0; i < 6; i++) {
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formatInfoBits1 = copyBit(i, 8, formatInfoBits1);
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}
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// .. and skip a bit in the timing pattern ...
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formatInfoBits1 = copyBit(7, 8, formatInfoBits1);
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formatInfoBits1 = copyBit(8, 8, formatInfoBits1);
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formatInfoBits1 = copyBit(8, 7, formatInfoBits1);
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// .. and skip a bit in the timing pattern ...
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for (int j = 5; j >= 0; j--) {
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formatInfoBits1 = copyBit(8, j, formatInfoBits1);
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}
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// Read the top-right/bottom-left pattern too
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int dimension = bitMatrix.getHeight();
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int formatInfoBits2 = 0;
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int jMin = dimension - 7;
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for (int j = dimension - 1; j >= jMin; j--) {
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formatInfoBits2 = copyBit(8, j, formatInfoBits2);
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}
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for (int i = dimension - 8; i < dimension; i++) {
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formatInfoBits2 = copyBit(i, 8, formatInfoBits2);
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}
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parsedFormatInfo = FormatInformation.decodeFormatInformation(formatInfoBits1, formatInfoBits2);
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if (parsedFormatInfo != null) {
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return parsedFormatInfo;
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}
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throw FormatException.getFormatInstance();
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}
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/**
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* <p>Reads version information from one of its two locations within the QR Code.</p>
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*
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* @return {@link Version} encapsulating the QR Code's version
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* @throws FormatException if both version information locations cannot be parsed as
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* the valid encoding of version information
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*/
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Version readVersion() throws FormatException {
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if (parsedVersion != null) {
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return parsedVersion;
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}
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int dimension = bitMatrix.getHeight();
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int provisionalVersion = (dimension - 17) >> 2;
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if (provisionalVersion <= 6) {
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return Version.getVersionForNumber(provisionalVersion);
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}
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// Read top-right version info: 3 wide by 6 tall
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int versionBits = 0;
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int ijMin = dimension - 11;
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for (int j = 5; j >= 0; j--) {
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for (int i = dimension - 9; i >= ijMin; i--) {
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versionBits = copyBit(i, j, versionBits);
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}
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}
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parsedVersion = Version.decodeVersionInformation(versionBits);
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if (parsedVersion != null && parsedVersion.getDimensionForVersion() == dimension) {
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return parsedVersion;
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}
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// Hmm, failed. Try bottom left: 6 wide by 3 tall
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versionBits = 0;
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for (int i = 5; i >= 0; i--) {
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for (int j = dimension - 9; j >= ijMin; j--) {
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versionBits = copyBit(i, j, versionBits);
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}
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}
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parsedVersion = Version.decodeVersionInformation(versionBits);
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if (parsedVersion != null && parsedVersion.getDimensionForVersion() == dimension) {
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return parsedVersion;
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}
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throw FormatException.getFormatInstance();
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}
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private int copyBit(int i, int j, int versionBits) {
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return bitMatrix.get(i, j) ? (versionBits << 1) | 0x1 : versionBits << 1;
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}
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/**
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* <p>Reads the bits in the {@link BitMatrix} representing the finder pattern in the
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* correct order in order to reconstitute the codewords bytes contained within the
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* QR Code.</p>
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*
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* @return bytes encoded within the QR Code
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* @throws FormatException if the exact number of bytes expected is not read
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*/
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byte[] readCodewords() throws FormatException {
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FormatInformation formatInfo = readFormatInformation();
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Version version = readVersion();
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// Get the data mask for the format used in this QR Code. This will exclude
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// some bits from reading as we wind through the bit matrix.
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DataMask dataMask = DataMask.forReference((int) formatInfo.getDataMask());
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int dimension = bitMatrix.getHeight();
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dataMask.unmaskBitMatrix(bitMatrix, dimension);
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BitMatrix functionPattern = version.buildFunctionPattern();
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boolean readingUp = true;
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byte[] result = new byte[version.getTotalCodewords()];
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int resultOffset = 0;
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int currentByte = 0;
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int bitsRead = 0;
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// Read columns in pairs, from right to left
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for (int j = dimension - 1; j > 0; j -= 2) {
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if (j == 6) {
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// Skip whole column with vertical alignment pattern;
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// saves time and makes the other code proceed more cleanly
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j--;
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}
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// Read alternatingly from bottom to top then top to bottom
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for (int count = 0; count < dimension; count++) {
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int i = readingUp ? dimension - 1 - count : count;
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for (int col = 0; col < 2; col++) {
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// Ignore bits covered by the function pattern
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if (!functionPattern.get(j - col, i)) {
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// Read a bit
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bitsRead++;
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currentByte <<= 1;
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if (bitMatrix.get(j - col, i)) {
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currentByte |= 1;
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}
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// If we've made a whole byte, save it off
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if (bitsRead == 8) {
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result[resultOffset++] = (byte) currentByte;
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bitsRead = 0;
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currentByte = 0;
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}
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}
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}
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}
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readingUp ^= true; // readingUp = !readingUp; // switch directions
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}
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if (resultOffset != version.getTotalCodewords()) {
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throw FormatException.getFormatInstance();
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}
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return result;
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}
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} |