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Core barcode encoding/decoding library
/*
* Copyright 2008 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.encoder;
import com.google.zxing.EncodeHintType;
import com.google.zxing.WriterException;
import com.google.zxing.common.BitArray;
import com.google.zxing.common.CharacterSetECI;
import com.google.zxing.common.reedsolomon.GenericGF;
import com.google.zxing.common.reedsolomon.ReedSolomonEncoder;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;
import com.google.zxing.qrcode.decoder.Mode;
import com.google.zxing.qrcode.decoder.Version;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Map;
/**
* @author [email protected] (Satoru Takabayashi) - creator
* @author [email protected] (Daniel Switkin) - ported from C++
*/
public final class Encoder {
// The original table is defined in the table 5 of JISX0510:2004 (p.19).
private static final int[] ALPHANUMERIC_TABLE = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0x00-0x0f
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0x10-0x1f
36, -1, -1, -1, 37, 38, -1, -1, -1, -1, 39, 40, -1, 41, 42, 43, // 0x20-0x2f
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 44, -1, -1, -1, -1, -1, // 0x30-0x3f
-1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, // 0x40-0x4f
25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1, -1, -1, // 0x50-0x5f
};
static final String DEFAULT_BYTE_MODE_ENCODING = "ISO-8859-1";
private Encoder() {
}
// The mask penalty calculation is complicated. See Table 21 of JISX0510:2004 (p.45) for details.
// Basically it applies four rules and summate all penalties.
private static int calculateMaskPenalty(ByteMatrix matrix) {
return MaskUtil.applyMaskPenaltyRule1(matrix)
+ MaskUtil.applyMaskPenaltyRule2(matrix)
+ MaskUtil.applyMaskPenaltyRule3(matrix)
+ MaskUtil.applyMaskPenaltyRule4(matrix);
}
/**
* Encode "bytes" with the error correction level "ecLevel". The encoding mode will be chosen
* internally by chooseMode(). On success, store the result in "qrCode".
*
* We recommend you to use QRCode.EC_LEVEL_L (the lowest level) for
* "getECLevel" since our primary use is to show QR code on desktop screens. We don't need very
* strong error correction for this purpose.
*
* Note that there is no way to encode bytes in MODE_KANJI. We might want to add EncodeWithMode()
* with which clients can specify the encoding mode. For now, we don't need the functionality.
*/
public static QRCode encode(String content, ErrorCorrectionLevel ecLevel) throws WriterException {
return encode(content, ecLevel, null);
}
public static QRCode encode(String content,
ErrorCorrectionLevel ecLevel,
Map hints) throws WriterException {
// Determine what character encoding has been specified by the caller, if any
String encoding = hints == null ? null : (String) hints.get(EncodeHintType.CHARACTER_SET);
if (encoding == null) {
encoding = DEFAULT_BYTE_MODE_ENCODING;
}
// Pick an encoding mode appropriate for the content. Note that this will not attempt to use
// multiple modes / segments even if that were more efficient. Twould be nice.
Mode mode = chooseMode(content, encoding);
// This will store the header information, like mode and
// length, as well as "header" segments like an ECI segment.
BitArray headerBits = new BitArray();
// Append ECI segment if applicable
if (mode == Mode.BYTE && !DEFAULT_BYTE_MODE_ENCODING.equals(encoding)) {
CharacterSetECI eci = CharacterSetECI.getCharacterSetECIByName(encoding);
if (eci != null) {
appendECI(eci, headerBits);
}
}
// (With ECI in place,) Write the mode marker
appendModeInfo(mode, headerBits);
// Collect data within the main segment, separately, to count its size if needed. Don't add it to
// main payload yet.
BitArray dataBits = new BitArray();
appendBytes(content, mode, dataBits, encoding);
// Hard part: need to know version to know how many bits length takes. But need to know how many
// bits it takes to know version. First we take a guess at version by assuming version will be
// the minimum, 1:
int provisionalBitsNeeded = headerBits.getSize()
+ mode.getCharacterCountBits(Version.getVersionForNumber(1))
+ dataBits.getSize();
Version provisionalVersion = chooseVersion(provisionalBitsNeeded, ecLevel);
// Use that guess to calculate the right version. I am still not sure this works in 100% of cases.
int bitsNeeded = headerBits.getSize()
+ mode.getCharacterCountBits(provisionalVersion)
+ dataBits.getSize();
Version version = chooseVersion(bitsNeeded, ecLevel);
BitArray headerAndDataBits = new BitArray();
headerAndDataBits.appendBitArray(headerBits);
// Find "length" of main segment and write it
int numLetters = mode == Mode.BYTE ? dataBits.getSizeInBytes() : content.length();
appendLengthInfo(numLetters, version, mode, headerAndDataBits);
// Put data together into the overall payload
headerAndDataBits.appendBitArray(dataBits);
Version.ECBlocks ecBlocks = version.getECBlocksForLevel(ecLevel);
int numDataBytes = version.getTotalCodewords() - ecBlocks.getTotalECCodewords();
// Terminate the bits properly.
terminateBits(numDataBytes, headerAndDataBits);
// Interleave data bits with error correction code.
BitArray finalBits = interleaveWithECBytes(headerAndDataBits,
version.getTotalCodewords(),
numDataBytes,
ecBlocks.getNumBlocks());
QRCode qrCode = new QRCode();
qrCode.setECLevel(ecLevel);
qrCode.setMode(mode);
qrCode.setVersion(version);
// Choose the mask pattern and set to "qrCode".
int dimension = version.getDimensionForVersion();
ByteMatrix matrix = new ByteMatrix(dimension, dimension);
int maskPattern = chooseMaskPattern(finalBits, ecLevel, version, matrix);
qrCode.setMaskPattern(maskPattern);
// Build the matrix and set it to "qrCode".
MatrixUtil.buildMatrix(finalBits, ecLevel, version, maskPattern, matrix);
qrCode.setMatrix(matrix);
return qrCode;
}
/**
* @return the code point of the table used in alphanumeric mode or
* -1 if there is no corresponding code in the table.
*/
static int getAlphanumericCode(int code) {
if (code < ALPHANUMERIC_TABLE.length) {
return ALPHANUMERIC_TABLE[code];
}
return -1;
}
public static Mode chooseMode(String content) {
return chooseMode(content, null);
}
/**
* Choose the best mode by examining the content. Note that 'encoding' is used as a hint;
* if it is Shift_JIS, and the input is only double-byte Kanji, then we return {@link Mode#KANJI}.
*/
private static Mode chooseMode(String content, String encoding) {
if ("Shift_JIS".equals(encoding)) {
// Choose Kanji mode if all input are double-byte characters
return isOnlyDoubleByteKanji(content) ? Mode.KANJI : Mode.BYTE;
}
boolean hasNumeric = false;
boolean hasAlphanumeric = false;
for (int i = 0; i < content.length(); ++i) {
char c = content.charAt(i);
if (c >= '0' && c <= '9') {
hasNumeric = true;
} else if (getAlphanumericCode(c) != -1) {
hasAlphanumeric = true;
} else {
return Mode.BYTE;
}
}
if (hasAlphanumeric) {
return Mode.ALPHANUMERIC;
}
if (hasNumeric) {
return Mode.NUMERIC;
}
return Mode.BYTE;
}
private static boolean isOnlyDoubleByteKanji(String content) {
byte[] bytes;
try {
bytes = content.getBytes("Shift_JIS");
} catch (UnsupportedEncodingException uee) {
return false;
}
int length = bytes.length;
if (length % 2 != 0) {
return false;
}
for (int i = 0; i < length; i += 2) {
int byte1 = bytes[i] & 0xFF;
if ((byte1 < 0x81 || byte1 > 0x9F) && (byte1 < 0xE0 || byte1 > 0xEB)) {
return false;
}
}
return true;
}
private static int chooseMaskPattern(BitArray bits,
ErrorCorrectionLevel ecLevel,
Version version,
ByteMatrix matrix) throws WriterException {
int minPenalty = Integer.MAX_VALUE; // Lower penalty is better.
int bestMaskPattern = -1;
// We try all mask patterns to choose the best one.
for (int maskPattern = 0; maskPattern < QRCode.NUM_MASK_PATTERNS; maskPattern++) {
MatrixUtil.buildMatrix(bits, ecLevel, version, maskPattern, matrix);
int penalty = calculateMaskPenalty(matrix);
if (penalty < minPenalty) {
minPenalty = penalty;
bestMaskPattern = maskPattern;
}
}
return bestMaskPattern;
}
private static Version chooseVersion(int numInputBits, ErrorCorrectionLevel ecLevel) throws WriterException {
// In the following comments, we use numbers of Version 7-H.
for (int versionNum = 1; versionNum <= 40; versionNum++) {
Version version = Version.getVersionForNumber(versionNum);
// numBytes = 196
int numBytes = version.getTotalCodewords();
// getNumECBytes = 130
Version.ECBlocks ecBlocks = version.getECBlocksForLevel(ecLevel);
int numEcBytes = ecBlocks.getTotalECCodewords();
// getNumDataBytes = 196 - 130 = 66
int numDataBytes = numBytes - numEcBytes;
int totalInputBytes = (numInputBits + 7) / 8;
if (numDataBytes >= totalInputBytes) {
return version;
}
}
throw new WriterException("Data too big");
}
/**
* Terminate bits as described in 8.4.8 and 8.4.9 of JISX0510:2004 (p.24).
*/
static void terminateBits(int numDataBytes, BitArray bits) throws WriterException {
int capacity = numDataBytes << 3;
if (bits.getSize() > capacity) {
throw new WriterException("data bits cannot fit in the QR Code" + bits.getSize() + " > " +
capacity);
}
for (int i = 0; i < 4 && bits.getSize() < capacity; ++i) {
bits.appendBit(false);
}
// Append termination bits. See 8.4.8 of JISX0510:2004 (p.24) for details.
// If the last byte isn't 8-bit aligned, we'll add padding bits.
int numBitsInLastByte = bits.getSize() & 0x07;
if (numBitsInLastByte > 0) {
for (int i = numBitsInLastByte; i < 8; i++) {
bits.appendBit(false);
}
}
// If we have more space, we'll fill the space with padding patterns defined in 8.4.9 (p.24).
int numPaddingBytes = numDataBytes - bits.getSizeInBytes();
for (int i = 0; i < numPaddingBytes; ++i) {
bits.appendBits((i & 0x01) == 0 ? 0xEC : 0x11, 8);
}
if (bits.getSize() != capacity) {
throw new WriterException("Bits size does not equal capacity");
}
}
/**
* Get number of data bytes and number of error correction bytes for block id "blockID". Store
* the result in "numDataBytesInBlock", and "numECBytesInBlock". See table 12 in 8.5.1 of
* JISX0510:2004 (p.30)
*/
static void getNumDataBytesAndNumECBytesForBlockID(int numTotalBytes,
int numDataBytes,
int numRSBlocks,
int blockID,
int[] numDataBytesInBlock,
int[] numECBytesInBlock) throws WriterException {
if (blockID >= numRSBlocks) {
throw new WriterException("Block ID too large");
}
// numRsBlocksInGroup2 = 196 % 5 = 1
int numRsBlocksInGroup2 = numTotalBytes % numRSBlocks;
// numRsBlocksInGroup1 = 5 - 1 = 4
int numRsBlocksInGroup1 = numRSBlocks - numRsBlocksInGroup2;
// numTotalBytesInGroup1 = 196 / 5 = 39
int numTotalBytesInGroup1 = numTotalBytes / numRSBlocks;
// numTotalBytesInGroup2 = 39 + 1 = 40
int numTotalBytesInGroup2 = numTotalBytesInGroup1 + 1;
// numDataBytesInGroup1 = 66 / 5 = 13
int numDataBytesInGroup1 = numDataBytes / numRSBlocks;
// numDataBytesInGroup2 = 13 + 1 = 14
int numDataBytesInGroup2 = numDataBytesInGroup1 + 1;
// numEcBytesInGroup1 = 39 - 13 = 26
int numEcBytesInGroup1 = numTotalBytesInGroup1 - numDataBytesInGroup1;
// numEcBytesInGroup2 = 40 - 14 = 26
int numEcBytesInGroup2 = numTotalBytesInGroup2 - numDataBytesInGroup2;
// Sanity checks.
// 26 = 26
if (numEcBytesInGroup1 != numEcBytesInGroup2) {
throw new WriterException("EC bytes mismatch");
}
// 5 = 4 + 1.
if (numRSBlocks != numRsBlocksInGroup1 + numRsBlocksInGroup2) {
throw new WriterException("RS blocks mismatch");
}
// 196 = (13 + 26) * 4 + (14 + 26) * 1
if (numTotalBytes !=
((numDataBytesInGroup1 + numEcBytesInGroup1) *
numRsBlocksInGroup1) +
((numDataBytesInGroup2 + numEcBytesInGroup2) *
numRsBlocksInGroup2)) {
throw new WriterException("Total bytes mismatch");
}
if (blockID < numRsBlocksInGroup1) {
numDataBytesInBlock[0] = numDataBytesInGroup1;
numECBytesInBlock[0] = numEcBytesInGroup1;
} else {
numDataBytesInBlock[0] = numDataBytesInGroup2;
numECBytesInBlock[0] = numEcBytesInGroup2;
}
}
/**
* Interleave "bits" with corresponding error correction bytes. On success, store the result in
* "result". The interleave rule is complicated. See 8.6 of JISX0510:2004 (p.37) for details.
*/
static BitArray interleaveWithECBytes(BitArray bits,
int numTotalBytes,
int numDataBytes,
int numRSBlocks) throws WriterException {
// "bits" must have "getNumDataBytes" bytes of data.
if (bits.getSizeInBytes() != numDataBytes) {
throw new WriterException("Number of bits and data bytes does not match");
}
// Step 1. Divide data bytes into blocks and generate error correction bytes for them. We'll
// store the divided data bytes blocks and error correction bytes blocks into "blocks".
int dataBytesOffset = 0;
int maxNumDataBytes = 0;
int maxNumEcBytes = 0;
// Since, we know the number of reedsolmon blocks, we can initialize the vector with the number.
Collection blocks = new ArrayList(numRSBlocks);
for (int i = 0; i < numRSBlocks; ++i) {
int[] numDataBytesInBlock = new int[1];
int[] numEcBytesInBlock = new int[1];
getNumDataBytesAndNumECBytesForBlockID(
numTotalBytes, numDataBytes, numRSBlocks, i,
numDataBytesInBlock, numEcBytesInBlock);
int size = numDataBytesInBlock[0];
byte[] dataBytes = new byte[size];
bits.toBytes(8*dataBytesOffset, dataBytes, 0, size);
byte[] ecBytes = generateECBytes(dataBytes, numEcBytesInBlock[0]);
blocks.add(new BlockPair(dataBytes, ecBytes));
maxNumDataBytes = Math.max(maxNumDataBytes, size);
maxNumEcBytes = Math.max(maxNumEcBytes, ecBytes.length);
dataBytesOffset += numDataBytesInBlock[0];
}
if (numDataBytes != dataBytesOffset) {
throw new WriterException("Data bytes does not match offset");
}
BitArray result = new BitArray();
// First, place data blocks.
for (int i = 0; i < maxNumDataBytes; ++i) {
for (BlockPair block : blocks) {
byte[] dataBytes = block.getDataBytes();
if (i < dataBytes.length) {
result.appendBits(dataBytes[i], 8);
}
}
}
// Then, place error correction blocks.
for (int i = 0; i < maxNumEcBytes; ++i) {
for (BlockPair block : blocks) {
byte[] ecBytes = block.getErrorCorrectionBytes();
if (i < ecBytes.length) {
result.appendBits(ecBytes[i], 8);
}
}
}
if (numTotalBytes != result.getSizeInBytes()) { // Should be same.
throw new WriterException("Interleaving error: " + numTotalBytes + " and " +
result.getSizeInBytes() + " differ.");
}
return result;
}
static byte[] generateECBytes(byte[] dataBytes, int numEcBytesInBlock) {
int numDataBytes = dataBytes.length;
int[] toEncode = new int[numDataBytes + numEcBytesInBlock];
for (int i = 0; i < numDataBytes; i++) {
toEncode[i] = dataBytes[i] & 0xFF;
}
new ReedSolomonEncoder(GenericGF.QR_CODE_FIELD_256).encode(toEncode, numEcBytesInBlock);
byte[] ecBytes = new byte[numEcBytesInBlock];
for (int i = 0; i < numEcBytesInBlock; i++) {
ecBytes[i] = (byte) toEncode[numDataBytes + i];
}
return ecBytes;
}
/**
* Append mode info. On success, store the result in "bits".
*/
static void appendModeInfo(Mode mode, BitArray bits) {
bits.appendBits(mode.getBits(), 4);
}
/**
* Append length info. On success, store the result in "bits".
*/
static void appendLengthInfo(int numLetters, Version version, Mode mode, BitArray bits) throws WriterException {
int numBits = mode.getCharacterCountBits(version);
if (numLetters >= (1 << numBits)) {
throw new WriterException(numLetters + " is bigger than " + ((1 << numBits) - 1));
}
bits.appendBits(numLetters, numBits);
}
/**
* Append "bytes" in "mode" mode (encoding) into "bits". On success, store the result in "bits".
*/
static void appendBytes(String content,
Mode mode,
BitArray bits,
String encoding) throws WriterException {
switch (mode) {
case NUMERIC:
appendNumericBytes(content, bits);
break;
case ALPHANUMERIC:
appendAlphanumericBytes(content, bits);
break;
case BYTE:
append8BitBytes(content, bits, encoding);
break;
case KANJI:
appendKanjiBytes(content, bits);
break;
default:
throw new WriterException("Invalid mode: " + mode);
}
}
static void appendNumericBytes(CharSequence content, BitArray bits) {
int length = content.length();
int i = 0;
while (i < length) {
int num1 = content.charAt(i) - '0';
if (i + 2 < length) {
// Encode three numeric letters in ten bits.
int num2 = content.charAt(i + 1) - '0';
int num3 = content.charAt(i + 2) - '0';
bits.appendBits(num1 * 100 + num2 * 10 + num3, 10);
i += 3;
} else if (i + 1 < length) {
// Encode two numeric letters in seven bits.
int num2 = content.charAt(i + 1) - '0';
bits.appendBits(num1 * 10 + num2, 7);
i += 2;
} else {
// Encode one numeric letter in four bits.
bits.appendBits(num1, 4);
i++;
}
}
}
static void appendAlphanumericBytes(CharSequence content, BitArray bits) throws WriterException {
int length = content.length();
int i = 0;
while (i < length) {
int code1 = getAlphanumericCode(content.charAt(i));
if (code1 == -1) {
throw new WriterException();
}
if (i + 1 < length) {
int code2 = getAlphanumericCode(content.charAt(i + 1));
if (code2 == -1) {
throw new WriterException();
}
// Encode two alphanumeric letters in 11 bits.
bits.appendBits(code1 * 45 + code2, 11);
i += 2;
} else {
// Encode one alphanumeric letter in six bits.
bits.appendBits(code1, 6);
i++;
}
}
}
static void append8BitBytes(String content, BitArray bits, String encoding)
throws WriterException {
byte[] bytes;
try {
bytes = content.getBytes(encoding);
} catch (UnsupportedEncodingException uee) {
throw new WriterException(uee);
}
for (byte b : bytes) {
bits.appendBits(b, 8);
}
}
static void appendKanjiBytes(String content, BitArray bits) throws WriterException {
byte[] bytes;
try {
bytes = content.getBytes("Shift_JIS");
} catch (UnsupportedEncodingException uee) {
throw new WriterException(uee);
}
int length = bytes.length;
for (int i = 0; i < length; i += 2) {
int byte1 = bytes[i] & 0xFF;
int byte2 = bytes[i + 1] & 0xFF;
int code = (byte1 << 8) | byte2;
int subtracted = -1;
if (code >= 0x8140 && code <= 0x9ffc) {
subtracted = code - 0x8140;
} else if (code >= 0xe040 && code <= 0xebbf) {
subtracted = code - 0xc140;
}
if (subtracted == -1) {
throw new WriterException("Invalid byte sequence");
}
int encoded = ((subtracted >> 8) * 0xc0) + (subtracted & 0xff);
bits.appendBits(encoded, 13);
}
}
private static void appendECI(CharacterSetECI eci, BitArray bits) {
bits.appendBits(Mode.ECI.getBits(), 4);
// This is correct for values up to 127, which is all we need now.
bits.appendBits(eci.getValue(), 8);
}
}
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