2 * Copyright 2008 Google Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 package com.google.zxing.oned;
19 import com.google.zxing.ReaderException;
20 import com.google.zxing.common.BitArray;
23 * <p>Implements decoding of the EAN-13 format.</p>
25 * @author dswitkin@google.com (Daniel Switkin)
26 * @author srowen@google.com (Sean Owen)
27 * @author alasdair@google.com (Alasdair Mackintosh)
29 public final class EAN13Reader extends AbstractUPCEANReader {
31 // For an EAN-13 barcode, the first digit is represented by the parities used
32 // to encode the next six digits, according to the table below. For example,
33 // if the barcode is 5 123456 789012 then the value of the first digit is
34 // signified by using odd for '1', even for '2', even for '3', odd for '4',
35 // odd for '5', and even for '6'. See http://en.wikipedia.org/wiki/EAN-13
37 // Parity of next 6 digits
39 // 0 Odd Odd Odd Odd Odd Odd
40 // 1 Odd Odd Even Odd Even Even
41 // 2 Odd Odd Even Even Odd Even
42 // 3 Odd Odd Even Even Even Odd
43 // 4 Odd Even Odd Odd Even Even
44 // 5 Odd Even Even Odd Odd Even
45 // 6 Odd Even Even Even Odd Odd
46 // 7 Odd Even Odd Even Odd Even
47 // 8 Odd Even Odd Even Even Odd
48 // 9 Odd Even Even Odd Even Odd
50 // Note that the encoding for '0' uses the same parity as a UPC barcode. Hence
51 // a UPC barcode can be converted to an EAN-13 barcode by prepending a 0.
53 // The encodong is represented by the following array, which is a bit pattern
54 // using Odd = 0 and Even = 1. For example, 5 is represented by:
56 // Odd Even Even Odd Odd Even
58 // 0 1 1 0 0 1 == 0x19
60 private static final int[] FIRST_DIGIT_ENCODINGS = {
61 0x00, 0x0B, 0x0D, 0xE, 0x13, 0x19, 0x1C, 0x15, 0x16, 0x1A
64 protected int decodeMiddle(BitArray row, int[] startRange, StringBuffer resultString) throws ReaderException {
66 int[] counters = new int[4];
67 int end = row.getSize();
68 int rowOffset = startRange[1];
70 int lgPatternFound = 0;
72 for (int x = 0; x < 6 && rowOffset < end; x++) {
73 int bestMatch = decodeDigit(row, counters, rowOffset, L_AND_G_PATTERNS);
74 resultString.append((char) ('0' + bestMatch % 10));
75 for (int i = 0; i < counters.length; i++) {
76 rowOffset += counters[i];
78 if (bestMatch >= 10) {
79 lgPatternFound |= 1 << (5 - x);
83 determineFirstDigit(resultString, lgPatternFound);
85 int[] middleRange = findGuardPattern(row, rowOffset, true, MIDDLE_PATTERN);
86 rowOffset = middleRange[1];
88 for (int x = 0; x < 6 && rowOffset < end; x++) {
89 int bestMatch = decodeDigit(row, counters, rowOffset, L_PATTERNS);
90 resultString.append((char) ('0' + bestMatch));
91 for (int i = 0; i < counters.length; i++) {
92 rowOffset += counters[i];
100 * Based on pattern of odd-even ('L' and 'G') patterns used to encoded the explicitly-encoded digits
101 * in a barcode, determines the implicitly encoded first digit and adds it to the result string.
103 * @param resultString string to insert decoded first digit into
104 * @param lgPatternFound int whose bits indicates the pattern of odd/even L/G patterns used to
106 * @throws ReaderException if first digit cannot be determined
108 private static void determineFirstDigit(StringBuffer resultString, int lgPatternFound) throws ReaderException {
109 for (int d = 0; d < 10; d++) {
110 if (lgPatternFound == FIRST_DIGIT_ENCODINGS[d]) {
111 // OK, if the first digit is a 0, then this is effectively also a UPC-A code.
112 // I think it's best (?) to go ahead and treat it as if it had matched as UPC-A, and return a result
113 // *without* the leading 0
115 resultString.insert(0, (char) ('0' + d));
120 throw new ReaderException("Unable to determine first digit");