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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.oned;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.ChecksumException;
import com.google.zxing.DecodeHintType;
import com.google.zxing.FormatException;
import com.google.zxing.NotFoundException;
import com.google.zxing.Result;
import com.google.zxing.ResultPoint;
import com.google.zxing.common.BitArray;
import java.util.Arrays;
import java.util.Map;
/**
* Decodes Code 39 barcodes. Supports "Full ASCII Code 39" if USE_CODE_39_EXTENDED_MODE is set.
*
* @author Sean Owen
* @see Code93Reader
*/
public final class Code39Reader extends OneDReader {
static final String ALPHABET_STRING = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. $/+%";
/**
* These represent the encodings of characters, as patterns of wide and narrow bars.
* The 9 least-significant bits of each int correspond to the pattern of wide and narrow,
* with 1s representing "wide" and 0s representing narrow.
*/
static final int[] CHARACTER_ENCODINGS = {
0x034, 0x121, 0x061, 0x160, 0x031, 0x130, 0x070, 0x025, 0x124, 0x064, // 0-9
0x109, 0x049, 0x148, 0x019, 0x118, 0x058, 0x00D, 0x10C, 0x04C, 0x01C, // A-J
0x103, 0x043, 0x142, 0x013, 0x112, 0x052, 0x007, 0x106, 0x046, 0x016, // K-T
0x181, 0x0C1, 0x1C0, 0x091, 0x190, 0x0D0, 0x085, 0x184, 0x0C4, 0x0A8, // U-$
0x0A2, 0x08A, 0x02A // /-%
};
static final int ASTERISK_ENCODING = 0x094;
private final boolean usingCheckDigit;
private final boolean extendedMode;
private final StringBuilder decodeRowResult;
private final int[] counters;
/**
* Creates a reader that assumes all encoded data is data, and does not treat the final
* character as a check digit. It will not decoded "extended Code 39" sequences.
*/
public Code39Reader() {
this(false);
}
/**
* Creates a reader that can be configured to check the last character as a check digit.
* It will not decoded "extended Code 39" sequences.
*
* @param usingCheckDigit if true, treat the last data character as a check digit, not
* data, and verify that the checksum passes.
*/
public Code39Reader(boolean usingCheckDigit) {
this(usingCheckDigit, false);
}
/**
* Creates a reader that can be configured to check the last character as a check digit,
* or optionally attempt to decode "extended Code 39" sequences that are used to encode
* the full ASCII character set.
*
* @param usingCheckDigit if true, treat the last data character as a check digit, not
* data, and verify that the checksum passes.
* @param extendedMode if true, will attempt to decode extended Code 39 sequences in the
* text.
*/
public Code39Reader(boolean usingCheckDigit, boolean extendedMode) {
this.usingCheckDigit = usingCheckDigit;
this.extendedMode = extendedMode;
decodeRowResult = new StringBuilder(20);
counters = new int[9];
}
@Override
public Result decodeRow(int rowNumber, BitArray row, Map hints)
throws NotFoundException, ChecksumException, FormatException {
int[] theCounters = counters;
Arrays.fill(theCounters, 0);
StringBuilder result = decodeRowResult;
result.setLength(0);
int[] start = findAsteriskPattern(row, theCounters);
// Read off white space
int nextStart = row.getNextSet(start[1]);
int end = row.getSize();
char decodedChar;
int lastStart;
do {
recordPattern(row, nextStart, theCounters);
int pattern = toNarrowWidePattern(theCounters);
if (pattern < 0) {
throw NotFoundException.getNotFoundInstance();
}
decodedChar = patternToChar(pattern);
result.append(decodedChar);
lastStart = nextStart;
for (int counter : theCounters) {
nextStart += counter;
}
// Read off white space
nextStart = row.getNextSet(nextStart);
} while (decodedChar != '*');
result.setLength(result.length() - 1); // remove asterisk
// Look for whitespace after pattern:
int lastPatternSize = 0;
for (int counter : theCounters) {
lastPatternSize += counter;
}
int whiteSpaceAfterEnd = nextStart - lastStart - lastPatternSize;
// If 50% of last pattern size, following last pattern, is not whitespace, fail
// (but if it's whitespace to the very end of the image, that's OK)
if (nextStart != end && (whiteSpaceAfterEnd * 2) < lastPatternSize) {
throw NotFoundException.getNotFoundInstance();
}
if (usingCheckDigit) {
int max = result.length() - 1;
int total = 0;
for (int i = 0; i < max; i++) {
total += ALPHABET_STRING.indexOf(decodeRowResult.charAt(i));
}
if (result.charAt(max) != ALPHABET_STRING.charAt(total % 43)) {
throw ChecksumException.getChecksumInstance();
}
result.setLength(max);
}
if (result.length() == 0) {
// false positive
throw NotFoundException.getNotFoundInstance();
}
String resultString;
if (extendedMode) {
resultString = decodeExtended(result);
} else {
resultString = result.toString();
}
float left = (start[1] + start[0]) / 2.0f;
float right = lastStart + lastPatternSize / 2.0f;
return new Result(
resultString,
null,
new ResultPoint[]{
new ResultPoint(left, rowNumber),
new ResultPoint(right, rowNumber)},
BarcodeFormat.CODE_39);
}
private static int[] findAsteriskPattern(BitArray row, int[] counters) throws NotFoundException {
int width = row.getSize();
int rowOffset = row.getNextSet(0);
int counterPosition = 0;
int patternStart = rowOffset;
boolean isWhite = false;
int patternLength = counters.length;
for (int i = rowOffset; i < width; i++) {
if (row.get(i) != isWhite) {
counters[counterPosition]++;
} else {
if (counterPosition == patternLength - 1) {
// Look for whitespace before start pattern, >= 50% of width of start pattern
if (toNarrowWidePattern(counters) == ASTERISK_ENCODING &&
row.isRange(Math.max(0, patternStart - ((i - patternStart) / 2)), patternStart, false)) {
return new int[]{patternStart, i};
}
patternStart += counters[0] + counters[1];
System.arraycopy(counters, 2, counters, 0, counterPosition - 1);
counters[counterPosition - 1] = 0;
counters[counterPosition] = 0;
counterPosition--;
} else {
counterPosition++;
}
counters[counterPosition] = 1;
isWhite = !isWhite;
}
}
throw NotFoundException.getNotFoundInstance();
}
// For efficiency, returns -1 on failure. Not throwing here saved as many as 700 exceptions
// per image when using some of our blackbox images.
private static int toNarrowWidePattern(int[] counters) {
int numCounters = counters.length;
int maxNarrowCounter = 0;
int wideCounters;
do {
int minCounter = Integer.MAX_VALUE;
for (int counter : counters) {
if (counter < minCounter && counter > maxNarrowCounter) {
minCounter = counter;
}
}
maxNarrowCounter = minCounter;
wideCounters = 0;
int totalWideCountersWidth = 0;
int pattern = 0;
for (int i = 0; i < numCounters; i++) {
int counter = counters[i];
if (counter > maxNarrowCounter) {
pattern |= 1 << (numCounters - 1 - i);
wideCounters++;
totalWideCountersWidth += counter;
}
}
if (wideCounters == 3) {
// Found 3 wide counters, but are they close enough in width?
// We can perform a cheap, conservative check to see if any individual
// counter is more than 1.5 times the average:
for (int i = 0; i < numCounters && wideCounters > 0; i++) {
int counter = counters[i];
if (counter > maxNarrowCounter) {
wideCounters--;
// totalWideCountersWidth = 3 * average, so this checks if counter >= 3/2 * average
if ((counter * 2) >= totalWideCountersWidth) {
return -1;
}
}
}
return pattern;
}
} while (wideCounters > 3);
return -1;
}
private static char patternToChar(int pattern) throws NotFoundException {
for (int i = 0; i < CHARACTER_ENCODINGS.length; i++) {
if (CHARACTER_ENCODINGS[i] == pattern) {
return ALPHABET_STRING.charAt(i);
}
}
if (pattern == ASTERISK_ENCODING) {
return '*';
}
throw NotFoundException.getNotFoundInstance();
}
private static String decodeExtended(CharSequence encoded) throws FormatException {
int length = encoded.length();
StringBuilder decoded = new StringBuilder(length);
for (int i = 0; i < length; i++) {
char c = encoded.charAt(i);
if (c == '+' || c == '$' || c == '%' || c == '/') {
char next = encoded.charAt(i + 1);
char decodedChar = '\0';
switch (c) {
case '+':
// +A to +Z map to a to z
if (next >= 'A' && next <= 'Z') {
decodedChar = (char) (next + 32);
} else {
throw FormatException.getFormatInstance();
}
break;
case '$':
// $A to $Z map to control codes SH to SB
if (next >= 'A' && next <= 'Z') {
decodedChar = (char) (next - 64);
} else {
throw FormatException.getFormatInstance();
}
break;
case '%':
// %A to %E map to control codes ESC to US
if (next >= 'A' && next <= 'E') {
decodedChar = (char) (next - 38);
} else if (next >= 'F' && next <= 'J') {
decodedChar = (char) (next - 11);
} else if (next >= 'K' && next <= 'O') {
decodedChar = (char) (next + 16);
} else if (next >= 'P' && next <= 'T') {
decodedChar = (char) (next + 43);
} else if (next == 'U') {
decodedChar = (char) 0;
} else if (next == 'V') {
decodedChar = '@';
} else if (next == 'W') {
decodedChar = '`';
} else if (next == 'X' || next == 'Y' || next == 'Z') {
decodedChar = (char) 127;
} else {
throw FormatException.getFormatInstance();
}
break;
case '/':
// /A to /O map to ! to , and /Z maps to :
if (next >= 'A' && next <= 'O') {
decodedChar = (char) (next - 32);
} else if (next == 'Z') {
decodedChar = ':';
} else {
throw FormatException.getFormatInstance();
}
break;
}
decoded.append(decodedChar);
// bump up i again since we read two characters
i++;
} else {
decoded.append(c);
}
}
return decoded.toString();
}
}