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.Result;
21 import com.google.zxing.ResultPoint;
22 import com.google.zxing.common.BitArray;
23 import com.google.zxing.common.GenericResultPoint;
26 * <p>Decodes Code 39 barcodes. This does not supported "Full ASCII Code 39" yet.</p>
28 * @author srowen@google.com (Sean Owen)
30 public final class Code39Reader extends AbstractOneDReader {
32 private static final String ALPHABET_STRING = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. *$/+%";
33 private static final char[] ALPHABET = ALPHABET_STRING.toCharArray();
36 * These represent the encodings of characters, as patterns of wide and narrow bars.
37 * The 9 least-significant bits of each int correspond to the pattern of wide and narrow,
38 * with 1s representing "wide" and 0s representing narrow.
40 private static final int[] CHARACTER_ENCODINGS = {
41 0x038, 0x121, 0x061, 0x160, 0x031, 0x130, 0x070, 0x025, 0x124, 0x064, // 0-9
42 0x109, 0x049, 0x148, 0x019, 0x118, 0x058, 0x00D, 0x10C, 0x04C, 0x01C, // A-J
43 0x103, 0x043, 0x142, 0x013, 0x112, 0x052, 0x007, 0x106, 0x046, 0x016, // K-T
44 0x181, 0x0C1, 0x1C0, 0x091, 0x190, 0x0D0, 0x085, 0x184, 0x0C4, 0x094, // U-*
45 0x0A8, 0x0A2, 0x08A, 0x02A // $-%
48 private static final int ASTERISK_ENCODING = CHARACTER_ENCODINGS[39];
50 private final boolean usingCheckDigit;
53 * Creates a reader that assumes all encoded data is data, and does not treat the final
54 * character as a check digit.
56 public Code39Reader() {
57 usingCheckDigit = false;
61 * Creates a reader that can be configured to check the last character as a check digit.
63 * @param usingCheckDigit if true, treat the last data character as a check digit, not
64 * data, and verify that the checksum passes
66 public Code39Reader(boolean usingCheckDigit) {
67 this.usingCheckDigit = usingCheckDigit;
70 public Result decodeRow(final int rowNumber, final BitArray row) throws ReaderException {
72 int[] start = findAsteriskPattern(row);
74 int nextStart = start[1];
76 int end = row.getSize();
78 // Read off white space
79 while (nextStart < end && !row.get(nextStart)) {
83 StringBuffer result = new StringBuffer();
84 int[] counters = new int[9];
88 recordPattern(row, nextStart, counters);
89 int pattern = toNarrowWidePattern(counters);
90 decodedChar = patternToChar(pattern);
91 result.append(decodedChar);
92 lastStart = nextStart;
93 for (int i = 0; i < counters.length; i++) {
94 nextStart += counters[i];
96 // Read off white space
97 while (nextStart < end && !row.get(nextStart)) {
100 } while (decodedChar != '*');
101 result.deleteCharAt(result.length() - 1); // remove asterisk
103 if (usingCheckDigit) {
104 int max = result.length() - 1;
106 for (int i = 0; i < max; i++) {
107 total += ALPHABET_STRING.indexOf(result.charAt(i));
109 if (total % 43 != ALPHABET_STRING.indexOf(result.charAt(max))) {
110 throw new ReaderException("Checksum failed");
112 result.deleteCharAt(max);
115 String resultString = result.toString();
116 return new Result(resultString,
117 new ResultPoint[]{new GenericResultPoint((float) (start[1] - start[0]) / 2.0f, (float) rowNumber),
118 new GenericResultPoint((float) (nextStart - lastStart) / 2.0f, (float) rowNumber)});
122 private static int[] findAsteriskPattern(BitArray row) throws ReaderException {
123 int width = row.getSize();
125 while (rowOffset < width) {
126 if (row.get(rowOffset)) {
132 int counterPosition = 0;
133 int[] counters = new int[9];
134 int patternStart = rowOffset;
135 boolean isWhite = false;
136 int patternLength = counters.length;
138 for (int i = rowOffset; i < width; i++) {
139 boolean pixel = row.get(i);
140 if ((!pixel && isWhite) || (pixel && !isWhite)) {
141 counters[counterPosition]++;
143 if (counterPosition == patternLength - 1) {
145 if (toNarrowWidePattern(counters) == ASTERISK_ENCODING) {
146 return new int[]{patternStart, i};
148 } catch (ReaderException re) {
149 // no match, continue
151 patternStart += counters[0] + counters[1];
152 for (int y = 2; y < patternLength; y++) {
153 counters[y - 2] = counters[y];
159 counters[counterPosition] = 1;
163 throw new ReaderException("Can't find pattern");
166 private static int toNarrowWidePattern(int[] counters) throws ReaderException {
167 int minCounter = Integer.MAX_VALUE;
168 for (int i = 0; i < counters.length; i++) {
169 if (counters[i] < minCounter) {
170 minCounter = counters[i];
173 int maxNarrowCounter = (int) (minCounter * 1.5f);
174 int wideCounters = 0;
176 for (int i = 0; i < counters.length; i++) {
177 if (counters[i] > maxNarrowCounter) {
178 pattern |= 1 << (counters.length - 1 - i);
182 if (wideCounters != 3) {
183 throw new ReaderException("Can't find 3 wide bars/spaces out of 9");
188 private static char patternToChar(int pattern) throws ReaderException {
189 for (int i = 0; i < CHARACTER_ENCODINGS.length; i++) {
190 if (CHARACTER_ENCODINGS[i] == pattern) {
194 throw new ReaderException("Pattern did not match character encoding");