2 * Copyright 2008 ZXing authors
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.BarcodeFormat;
21 import com.google.zxing.common.BitArray;
24 * <p>Implements decoding of the EAN-13 format.</p>
26 * @author dswitkin@google.com (Daniel Switkin)
27 * @author srowen@google.com (Sean Owen)
28 * @author alasdair@google.com (Alasdair Mackintosh)
30 public final class EAN13Reader extends AbstractUPCEANReader {
32 // For an EAN-13 barcode, the first digit is represented by the parities used
33 // to encode the next six digits, according to the table below. For example,
34 // if the barcode is 5 123456 789012 then the value of the first digit is
35 // signified by using odd for '1', even for '2', even for '3', odd for '4',
36 // odd for '5', and even for '6'. See http://en.wikipedia.org/wiki/EAN-13
38 // Parity of next 6 digits
40 // 0 Odd Odd Odd Odd Odd Odd
41 // 1 Odd Odd Even Odd Even Even
42 // 2 Odd Odd Even Even Odd Even
43 // 3 Odd Odd Even Even Even Odd
44 // 4 Odd Even Odd Odd Even Even
45 // 5 Odd Even Even Odd Odd Even
46 // 6 Odd Even Even Even Odd Odd
47 // 7 Odd Even Odd Even Odd Even
48 // 8 Odd Even Odd Even Even Odd
49 // 9 Odd Even Even Odd Even Odd
51 // Note that the encoding for '0' uses the same parity as a UPC barcode. Hence
52 // a UPC barcode can be converted to an EAN-13 barcode by prepending a 0.
54 // The encodong is represented by the following array, which is a bit pattern
55 // using Odd = 0 and Even = 1. For example, 5 is represented by:
57 // Odd Even Even Odd Odd Even
59 // 0 1 1 0 0 1 == 0x19
61 private static final int[] FIRST_DIGIT_ENCODINGS = {
62 0x00, 0x0B, 0x0D, 0xE, 0x13, 0x19, 0x1C, 0x15, 0x16, 0x1A
65 protected int decodeMiddle(BitArray row, int[] startRange, StringBuffer resultString) throws ReaderException {
67 int[] counters = new int[4];
68 int end = row.getSize();
69 int rowOffset = startRange[1];
71 int lgPatternFound = 0;
73 for (int x = 0; x < 6 && rowOffset < end; x++) {
74 int bestMatch = decodeDigit(row, counters, rowOffset, L_AND_G_PATTERNS);
75 resultString.append((char) ('0' + bestMatch % 10));
76 for (int i = 0; i < counters.length; i++) {
77 rowOffset += counters[i];
79 if (bestMatch >= 10) {
80 lgPatternFound |= 1 << (5 - x);
84 determineFirstDigit(resultString, lgPatternFound);
86 int[] middleRange = findGuardPattern(row, rowOffset, true, MIDDLE_PATTERN);
87 rowOffset = middleRange[1];
89 for (int x = 0; x < 6 && rowOffset < end; x++) {
90 int bestMatch = decodeDigit(row, counters, rowOffset, L_PATTERNS);
91 resultString.append((char) ('0' + bestMatch));
92 for (int i = 0; i < counters.length; i++) {
93 rowOffset += counters[i];
100 BarcodeFormat getBarcodeFormat() {
101 return BarcodeFormat.EAN_13;
105 * Based on pattern of odd-even ('L' and 'G') patterns used to encoded the explicitly-encoded digits
106 * in a barcode, determines the implicitly encoded first digit and adds it to the result string.
108 * @param resultString string to insert decoded first digit into
109 * @param lgPatternFound int whose bits indicates the pattern of odd/even L/G patterns used to
111 * @throws ReaderException if first digit cannot be determined
113 private static void determineFirstDigit(StringBuffer resultString, int lgPatternFound) throws ReaderException {
114 for (int d = 0; d < 10; d++) {
115 if (lgPatternFound == FIRST_DIGIT_ENCODINGS[d]) {
116 resultString.insert(0, (char) ('0' + d));
120 throw new ReaderException("Unable to determine first digit");