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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.DecodeHintType;
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 Codabar barcodes.
*
* @author Bas Vijfwinkel
* @author David Walker
*/
public final class CodaBarReader extends OneDReader {
// These values are critical for determining how permissive the decoding
// will be. All stripe sizes must be within the window these define, as
// compared to the average stripe size.
private static final int MAX_ACCEPTABLE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 2.0f);
private static final int PADDING = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 1.5f);
private static final String ALPHABET_STRING = "0123456789-$:/.+ABCD";
static final char[] ALPHABET = ALPHABET_STRING.toCharArray();
/**
* These represent the encodings of characters, as patterns of wide and narrow bars. The 7 least-significant bits of
* each int correspond to the pattern of wide and narrow, with 1s representing "wide" and 0s representing narrow.
*/
static final int[] CHARACTER_ENCODINGS = {
0x003, 0x006, 0x009, 0x060, 0x012, 0x042, 0x021, 0x024, 0x030, 0x048, // 0-9
0x00c, 0x018, 0x045, 0x051, 0x054, 0x015, 0x01A, 0x029, 0x00B, 0x00E, // -$:/.+ABCD
};
// minimal number of characters that should be present (inclusing start and stop characters)
// under normal circumstances this should be set to 3, but can be set higher
// as a last-ditch attempt to reduce false positives.
private static final int MIN_CHARACTER_LENGTH = 3;
// official start and end patterns
private static final char[] STARTEND_ENCODING = {'A', 'B', 'C', 'D'};
// some codabar generator allow the codabar string to be closed by every
// character. This will cause lots of false positives!
// some industries use a checksum standard but this is not part of the original codabar standard
// for more information see : http://www.mecsw.com/specs/codabar.html
// Keep some instance variables to avoid reallocations
private final StringBuilder decodeRowResult;
private int[] counters;
private int counterLength;
public CodaBarReader() {
decodeRowResult = new StringBuilder(20);
counters = new int[80];
counterLength = 0;
}
@Override
public Result decodeRow(int rowNumber, BitArray row, Map hints) throws NotFoundException {
Arrays.fill(counters, 0);
setCounters(row);
int startOffset = findStartPattern();
int nextStart = startOffset;
decodeRowResult.setLength(0);
do {
int charOffset = toNarrowWidePattern(nextStart);
if (charOffset == -1) {
throw NotFoundException.getNotFoundInstance();
}
// Hack: We store the position in the alphabet table into a
// StringBuilder, so that we can access the decoded patterns in
// validatePattern. We'll translate to the actual characters later.
decodeRowResult.append((char)charOffset);
nextStart += 8;
// Stop as soon as we see the end character.
if (decodeRowResult.length() > 1 &&
arrayContains(STARTEND_ENCODING, ALPHABET[charOffset])) {
break;
}
} while (nextStart < counterLength); // no fixed end pattern so keep on reading while data is available
// Look for whitespace after pattern:
int trailingWhitespace = counters[nextStart - 1];
int lastPatternSize = 0;
for (int i = -8; i < -1; i++) {
lastPatternSize += counters[nextStart + i];
}
// We need to see whitespace equal to 50% of the last pattern size,
// otherwise this is probably a false positive. The exception is if we are
// at the end of the row. (I.e. the barcode barely fits.)
if (nextStart < counterLength && trailingWhitespace < lastPatternSize / 2) {
throw NotFoundException.getNotFoundInstance();
}
validatePattern(startOffset);
// Translate character table offsets to actual characters.
for (int i = 0; i < decodeRowResult.length(); i++) {
decodeRowResult.setCharAt(i, ALPHABET[decodeRowResult.charAt(i)]);
}
// Ensure a valid start and end character
char startchar = decodeRowResult.charAt(0);
if (!arrayContains(STARTEND_ENCODING, startchar)) {
throw NotFoundException.getNotFoundInstance();
}
char endchar = decodeRowResult.charAt(decodeRowResult.length() - 1);
if (!arrayContains(STARTEND_ENCODING, endchar)) {
throw NotFoundException.getNotFoundInstance();
}
// remove stop/start characters character and check if a long enough string is contained
if (decodeRowResult.length() <= MIN_CHARACTER_LENGTH) {
// Almost surely a false positive ( start + stop + at least 1 character)
throw NotFoundException.getNotFoundInstance();
}
decodeRowResult.deleteCharAt(decodeRowResult.length() - 1);
decodeRowResult.deleteCharAt(0);
int runningCount = 0;
for (int i = 0; i < startOffset; i++) {
runningCount += counters[i];
}
float left = (float) runningCount;
for (int i = startOffset; i < nextStart - 1; i++) {
runningCount += counters[i];
}
float right = (float) runningCount;
return new Result(
decodeRowResult.toString(),
null,
new ResultPoint[]{
new ResultPoint(left, (float) rowNumber),
new ResultPoint(right, (float) rowNumber)},
BarcodeFormat.CODABAR);
}
void validatePattern(int start) throws NotFoundException {
// First, sum up the total size of our four categories of stripe sizes;
int[] sizes = {0, 0, 0, 0};
int[] counts = {0, 0, 0, 0};
int end = decodeRowResult.length() - 1;
// We break out of this loop in the middle, in order to handle
// inter-character spaces properly.
int pos = start;
for (int i = 0; true; i++) {
int pattern = CHARACTER_ENCODINGS[decodeRowResult.charAt(i)];
for (int j = 6; j >= 0; j--) {
// Even j = bars, while odd j = spaces. Categories 2 and 3 are for
// long stripes, while 0 and 1 are for short stripes.
int category = (j & 1) + (pattern & 1) * 2;
sizes[category] += counters[pos + j];
counts[category]++;
pattern >>= 1;
}
if (i >= end) {
break;
}
// We ignore the inter-character space - it could be of any size.
pos += 8;
}
// Calculate our allowable size thresholds using fixed-point math.
int[] maxes = new int[4];
int[] mins = new int[4];
// Define the threshold of acceptability to be the midpoint between the
// average small stripe and the average large stripe. No stripe lengths
// should be on the "wrong" side of that line.
for (int i = 0; i < 2; i++) {
mins[i] = 0; // Accept arbitrarily small "short" stripes.
mins[i + 2] = ((sizes[i] << INTEGER_MATH_SHIFT) / counts[i] +
(sizes[i + 2] << INTEGER_MATH_SHIFT) / counts[i + 2]) >> 1;
maxes[i] = mins[i + 2];
maxes[i + 2] = (sizes[i + 2] * MAX_ACCEPTABLE + PADDING) / counts[i + 2];
}
// Now verify that all of the stripes are within the thresholds.
pos = start;
for (int i = 0; true; i++) {
int pattern = CHARACTER_ENCODINGS[decodeRowResult.charAt(i)];
for (int j = 6; j >= 0; j--) {
// Even j = bars, while odd j = spaces. Categories 2 and 3 are for
// long stripes, while 0 and 1 are for short stripes.
int category = (j & 1) + (pattern & 1) * 2;
int size = counters[pos + j] << INTEGER_MATH_SHIFT;
if (size < mins[category] || size > maxes[category]) {
throw NotFoundException.getNotFoundInstance();
}
pattern >>= 1;
}
if (i >= end) {
break;
}
pos += 8;
}
}
/**
* Records the size of all runs of white and black pixels, starting with white.
* This is just like recordPattern, except it records all the counters, and
* uses our builtin "counters" member for storage.
* @param row row to count from
*/
private void setCounters(BitArray row) throws NotFoundException {
counterLength = 0;
// Start from the first white bit.
int i = row.getNextUnset(0);
int end = row.getSize();
if (i >= end) {
throw NotFoundException.getNotFoundInstance();
}
boolean isWhite = true;
int count = 0;
for (; i < end; i++) {
if (row.get(i) ^ isWhite) { // that is, exactly one is true
count++;
} else {
counterAppend(count);
count = 1;
isWhite = !isWhite;
}
}
counterAppend(count);
}
private void counterAppend(int e) {
counters[counterLength] = e;
counterLength++;
if (counterLength >= counters.length) {
int[] temp = new int[counterLength * 2];
System.arraycopy(counters, 0, temp, 0, counterLength);
counters = temp;
}
}
private int findStartPattern() throws NotFoundException {
for (int i = 1; i < counterLength; i += 2) {
int charOffset = toNarrowWidePattern(i);
if (charOffset != -1 && arrayContains(STARTEND_ENCODING, ALPHABET[charOffset])) {
// Look for whitespace before start pattern, >= 50% of width of start pattern
// We make an exception if the whitespace is the first element.
int patternSize = 0;
for (int j = i; j < i + 7; j++) {
patternSize += counters[j];
}
if (i == 1 || counters[i-1] >= patternSize / 2) {
return i;
}
}
}
throw NotFoundException.getNotFoundInstance();
}
static boolean arrayContains(char[] array, char key) {
if (array != null) {
for (char c : array) {
if (c == key) {
return true;
}
}
}
return false;
}
// Assumes that counters[position] is a bar.
private int toNarrowWidePattern(int position) {
int end = position + 7;
if (end >= counterLength) {
return -1;
}
int[] theCounters = counters;
int maxBar = 0;
int minBar = Integer.MAX_VALUE;
for (int j = position; j < end; j += 2) {
int currentCounter = theCounters[j];
if (currentCounter < minBar) {
minBar = currentCounter;
}
if (currentCounter > maxBar) {
maxBar = currentCounter;
}
}
int thresholdBar = (minBar + maxBar) / 2;
int maxSpace = 0;
int minSpace = Integer.MAX_VALUE;
for (int j = position + 1; j < end; j += 2) {
int currentCounter = theCounters[j];
if (currentCounter < minSpace) {
minSpace = currentCounter;
}
if (currentCounter > maxSpace) {
maxSpace = currentCounter;
}
}
int thresholdSpace = (minSpace + maxSpace) / 2;
int bitmask = 1 << 7;
int pattern = 0;
for (int i = 0; i < 7; i++) {
int threshold = (i & 1) == 0 ? thresholdBar : thresholdSpace;
bitmask >>= 1;
if (theCounters[position + i] > threshold) {
pattern |= bitmask;
}
}
for (int i = 0; i < CHARACTER_ENCODINGS.length; i++) {
if (CHARACTER_ENCODINGS[i] == pattern) {
return i;
}
}
return -1;
}
}
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