com.google.zxing.qrcode.decoder.BitMatrixParser Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of core Show documentation
Show all versions of core Show documentation
Core barcode encoding/decoding library
/*
* 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 com.google.zxing.FormatException;
import com.google.zxing.common.BitMatrix;
/**
* @author Sean Owen
*/
final class BitMatrixParser {
private final BitMatrix bitMatrix;
private Version parsedVersion;
private FormatInformation parsedFormatInfo;
private boolean mirror;
/**
* @param bitMatrix {@link BitMatrix} to parse
* @throws FormatException if dimension is not >= 21 and 1 mod 4
*/
BitMatrixParser(BitMatrix bitMatrix) throws FormatException {
int dimension = bitMatrix.getHeight();
if (dimension < 21 || (dimension & 0x03) != 1) {
throw FormatException.getFormatInstance();
}
this.bitMatrix = bitMatrix;
}
/**
* Reads format information from one of its two locations within the QR Code.
*
* @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
*/
FormatInformation readFormatInformation() throws FormatException {
if (parsedFormatInfo != null) {
return parsedFormatInfo;
}
// Read top-left format info bits
int formatInfoBits1 = 0;
for (int i = 0; i < 6; i++) {
formatInfoBits1 = copyBit(i, 8, formatInfoBits1);
}
// .. and skip a bit in the timing pattern ...
formatInfoBits1 = copyBit(7, 8, formatInfoBits1);
formatInfoBits1 = copyBit(8, 8, formatInfoBits1);
formatInfoBits1 = copyBit(8, 7, formatInfoBits1);
// .. and skip a bit in the timing pattern ...
for (int j = 5; j >= 0; j--) {
formatInfoBits1 = copyBit(8, j, formatInfoBits1);
}
// Read the top-right/bottom-left pattern too
int dimension = bitMatrix.getHeight();
int formatInfoBits2 = 0;
int jMin = dimension - 7;
for (int j = dimension - 1; j >= jMin; j--) {
formatInfoBits2 = copyBit(8, j, formatInfoBits2);
}
for (int i = dimension - 8; i < dimension; i++) {
formatInfoBits2 = copyBit(i, 8, formatInfoBits2);
}
parsedFormatInfo = FormatInformation.decodeFormatInformation(formatInfoBits1, formatInfoBits2);
if (parsedFormatInfo != null) {
return parsedFormatInfo;
}
throw FormatException.getFormatInstance();
}
/**
* Reads version information from one of its two locations within the QR Code.
*
* @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
*/
Version readVersion() throws FormatException {
if (parsedVersion != null) {
return parsedVersion;
}
int dimension = bitMatrix.getHeight();
int provisionalVersion = (dimension - 17) >> 2;
if (provisionalVersion <= 6) {
return Version.getVersionForNumber(provisionalVersion);
}
// Read top-right version info: 3 wide by 6 tall
int versionBits = 0;
int ijMin = dimension - 11;
for (int j = 5; j >= 0; j--) {
for (int i = dimension - 9; i >= ijMin; i--) {
versionBits = copyBit(i, j, versionBits);
}
}
Version theParsedVersion = Version.decodeVersionInformation(versionBits);
if (theParsedVersion != null && theParsedVersion.getDimensionForVersion() == dimension) {
parsedVersion = theParsedVersion;
return theParsedVersion;
}
// Hmm, failed. Try bottom left: 6 wide by 3 tall
versionBits = 0;
for (int i = 5; i >= 0; i--) {
for (int j = dimension - 9; j >= ijMin; j--) {
versionBits = copyBit(i, j, versionBits);
}
}
theParsedVersion = Version.decodeVersionInformation(versionBits);
if (theParsedVersion != null && theParsedVersion.getDimensionForVersion() == dimension) {
parsedVersion = theParsedVersion;
return theParsedVersion;
}
throw FormatException.getFormatInstance();
}
private int copyBit(int i, int j, int versionBits) {
boolean bit = mirror ? bitMatrix.get(j, i) : bitMatrix.get(i, j);
return bit ? (versionBits << 1) | 0x1 : versionBits << 1;
}
/**
* 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.
*
* @return bytes encoded within the QR Code
* @throws FormatException if the exact number of bytes expected is not read
*/
byte[] readCodewords() throws FormatException {
FormatInformation formatInfo = readFormatInformation();
Version version = 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.
DataMask dataMask = DataMask.forReference(formatInfo.getDataMask());
int dimension = bitMatrix.getHeight();
dataMask.unmaskBitMatrix(bitMatrix, dimension);
BitMatrix functionPattern = version.buildFunctionPattern();
boolean readingUp = true;
byte[] result = new byte[version.getTotalCodewords()];
int resultOffset = 0;
int currentByte = 0;
int bitsRead = 0;
// Read columns in pairs, from right to left
for (int 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 (int count = 0; count < dimension; count++) {
int i = readingUp ? dimension - 1 - count : count;
for (int 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 (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 ^= true; // readingUp = !readingUp; // switch directions
}
if (resultOffset != version.getTotalCodewords()) {
throw FormatException.getFormatInstance();
}
return result;
}
/**
* Revert the mask removal done while reading the code words. The bit matrix should revert to its original state.
*/
void remask() {
if (parsedFormatInfo == null) {
return; // We have no format information, and have no data mask
}
DataMask dataMask = DataMask.forReference(parsedFormatInfo.getDataMask());
int dimension = bitMatrix.getHeight();
dataMask.unmaskBitMatrix(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.
*/
void setMirror(boolean mirror) {
parsedVersion = null;
parsedFormatInfo = null;
this.mirror = mirror;
}
/** Mirror the bit matrix in order to attempt a second reading. */
void mirror() {
for (int x = 0; x < bitMatrix.getWidth(); x++) {
for (int y = x + 1; y < bitMatrix.getHeight(); y++) {
if (bitMatrix.get(x, y) != bitMatrix.get(y, x)) {
bitMatrix.flip(y, x);
bitMatrix.flip(x, y);
}
}
}
}
}
© 2015 - 2024 Weber Informatics LLC | Privacy Policy