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.BarcodeFormat;
20 import com.google.zxing.ReaderException;
21 import com.google.zxing.Result;
22 import com.google.zxing.ResultPoint;
23 import com.google.zxing.common.BitArray;
24 import com.google.zxing.common.GenericResultPoint;
26 import java.util.Hashtable;
29 * <p>Decodes Code 39 barcodes. This does not support "Full ASCII Code 39" yet.</p>
31 * @author srowen@google.com (Sean Owen)
33 public final class Code39Reader extends AbstractOneDReader {
35 private static final String ALPHABET_STRING = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. *$/+%";
36 private static final char[] ALPHABET = ALPHABET_STRING.toCharArray();
39 * These represent the encodings of characters, as patterns of wide and narrow bars.
40 * The 9 least-significant bits of each int correspond to the pattern of wide and narrow,
41 * with 1s representing "wide" and 0s representing narrow.
43 private static final int[] CHARACTER_ENCODINGS = {
44 0x034, 0x121, 0x061, 0x160, 0x031, 0x130, 0x070, 0x025, 0x124, 0x064, // 0-9
45 0x109, 0x049, 0x148, 0x019, 0x118, 0x058, 0x00D, 0x10C, 0x04C, 0x01C, // A-J
46 0x103, 0x043, 0x142, 0x013, 0x112, 0x052, 0x007, 0x106, 0x046, 0x016, // K-T
47 0x181, 0x0C1, 0x1C0, 0x091, 0x190, 0x0D0, 0x085, 0x184, 0x0C4, 0x094, // U-*
48 0x0A8, 0x0A2, 0x08A, 0x02A // $-%
51 private static final int ASTERISK_ENCODING = CHARACTER_ENCODINGS[39];
53 private final boolean usingCheckDigit;
54 private final boolean extendedMode;
57 * Creates a reader that assumes all encoded data is data, and does not treat the final
58 * character as a check digit. It will not decoded "extended Code 39" sequences.
60 public Code39Reader() {
61 usingCheckDigit = false;
66 * Creates a reader that can be configured to check the last character as a check digit.
67 * It will not decoded "extended Code 39" sequences.
69 * @param usingCheckDigit if true, treat the last data character as a check digit, not
70 * data, and verify that the checksum passes.
72 public Code39Reader(boolean usingCheckDigit) {
73 this.usingCheckDigit = usingCheckDigit;
74 this.extendedMode = false;
78 * Creates a reader that can be configured to check the last character as a check digit,
79 * or optionally attempt to decode "extended Code 39" sequences that are used to encode
80 * the full ASCII character set.
82 * @param usingCheckDigit if true, treat the last data character as a check digit, not
83 * data, and verify that the checksum passes.
84 * @param extendedMode if true, will attempt to decode extended Code 39 sequences in the
87 public Code39Reader(boolean usingCheckDigit, boolean extendedMode) {
88 this.usingCheckDigit = usingCheckDigit;
89 this.extendedMode = extendedMode;
92 public Result decodeRow(int rowNumber, BitArray row, Hashtable hints) throws ReaderException {
94 int[] start = findAsteriskPattern(row);
96 int nextStart = start[1];
98 int end = row.getSize();
100 // Read off white space
101 while (nextStart < end && !row.get(nextStart)) {
105 StringBuffer result = new StringBuffer();
106 int[] counters = new int[9];
110 recordPattern(row, nextStart, counters);
111 int pattern = toNarrowWidePattern(counters);
112 decodedChar = patternToChar(pattern);
113 result.append(decodedChar);
114 lastStart = nextStart;
115 for (int i = 0; i < counters.length; i++) {
116 nextStart += counters[i];
118 // Read off white space
119 while (nextStart < end && !row.get(nextStart)) {
122 } while (decodedChar != '*');
123 result.deleteCharAt(result.length() - 1); // remove asterisk
125 // Look for whitespace after pattern:
126 int lastPatternSize = 0;
127 for (int i = 0; i < counters.length; i++) {
128 lastPatternSize += counters[i];
130 int whiteSpaceAfterEnd = nextStart - lastStart - lastPatternSize;
131 // If 50% of last pattern size, following last pattern, is not whitespace, fail
132 // (but if it's whitespace to the very end of the image, that's OK)
133 if (nextStart != end && whiteSpaceAfterEnd / 2 < lastPatternSize) {
134 throw new ReaderException("Pattern not followed by whitespace");
137 if (usingCheckDigit) {
138 int max = result.length() - 1;
140 for (int i = 0; i < max; i++) {
141 total += ALPHABET_STRING.indexOf(result.charAt(i));
143 if (total % 43 != ALPHABET_STRING.indexOf(result.charAt(max))) {
144 throw new ReaderException("Checksum failed");
146 result.deleteCharAt(max);
149 String resultString = result.toString();
151 resultString = decodeExtended(resultString);
154 if (resultString.length() == 0) {
155 // Almost surely a false positive
156 throw new ReaderException("Empty barcode found; assuming a false positive");
159 float left = (float) (start[1] + start[0]) / 2.0f;
160 float right = (float) (nextStart + lastStart) / 2.0f;
165 new GenericResultPoint(left, (float) rowNumber),
166 new GenericResultPoint(right, (float) rowNumber)},
167 BarcodeFormat.CODE_39);
171 private static int[] findAsteriskPattern(BitArray row) throws ReaderException {
172 int width = row.getSize();
174 while (rowOffset < width) {
175 if (row.get(rowOffset)) {
181 int counterPosition = 0;
182 int[] counters = new int[9];
183 int patternStart = rowOffset;
184 boolean isWhite = false;
185 int patternLength = counters.length;
187 for (int i = rowOffset; i < width; i++) {
188 boolean pixel = row.get(i);
189 if ((!pixel && isWhite) || (pixel && !isWhite)) {
190 counters[counterPosition]++;
192 if (counterPosition == patternLength - 1) {
194 if (toNarrowWidePattern(counters) == ASTERISK_ENCODING) {
195 // Look for whitespace before start pattern, >= 50% of width of start pattern
196 if (row.isRange(Math.max(0, patternStart - (i - patternStart) / 2), patternStart, false)) {
197 return new int[]{patternStart, i};
200 } catch (ReaderException re) {
201 // no match, continue
203 patternStart += counters[0] + counters[1];
204 for (int y = 2; y < patternLength; y++) {
205 counters[y - 2] = counters[y];
207 counters[patternLength - 2] = 0;
208 counters[patternLength - 1] = 0;
213 counters[counterPosition] = 1;
217 throw new ReaderException("Can't find pattern");
220 private static int toNarrowWidePattern(int[] counters) throws ReaderException {
221 int numCounters = counters.length;
222 int maxNarrowCounter = 0;
225 int minCounter = Integer.MAX_VALUE;
226 for (int i = 0; i < numCounters; i++) {
227 int counter = counters[i];
228 if (counter < minCounter && counter > maxNarrowCounter) {
229 minCounter = counter;
232 maxNarrowCounter = minCounter;
234 int totalWideCountersWidth = 0;
236 for (int i = 0; i < numCounters; i++) {
237 int counter = counters[i];
238 if (counters[i] > maxNarrowCounter) {
239 pattern |= 1 << (numCounters - 1 - i);
241 totalWideCountersWidth += counter;
244 if (wideCounters == 3) {
245 // Found 3 wide counters, but are they close enough in width?
246 // We can perform a cheap, conservative check to see if any individual
247 // counter is more than 1.5 times the average:
248 for (int i = 0; i < numCounters && wideCounters > 0; i++) {
249 int counter = counters[i];
250 if (counters[i] > maxNarrowCounter) {
252 // totalWideCountersWidth = 3 * average, so this checks if counter >= 3/2 * average
253 if ((counter << 1) >= totalWideCountersWidth) {
254 throw new ReaderException("Wide bars vary too much in width, rejecting");
260 } while (wideCounters > 3);
261 throw new ReaderException("Can't find 3 wide bars/spaces out of 9");
264 private static char patternToChar(int pattern) throws ReaderException {
265 for (int i = 0; i < CHARACTER_ENCODINGS.length; i++) {
266 if (CHARACTER_ENCODINGS[i] == pattern) {
270 throw new ReaderException("Pattern did not match character encoding");
273 private static String decodeExtended(String encoded) throws ReaderException {
274 int length = encoded.length();
275 StringBuffer decoded = new StringBuffer(length);
276 for (int i = 0; i < length; i++) {
277 char c = encoded.charAt(i);
278 if (c == '+' || c == '$' || c == '%' || c == '/') {
279 char next = encoded.charAt(i + 1);
280 char decodedChar = '\0';
283 // +A to +Z map to a to z
284 if (next >= 'A' && next <= 'Z') {
285 decodedChar = (char) (next + 32);
287 throw new ReaderException("Invalid extended code 39 sequence: " + c + next);
291 // $A to $Z map to control codes SH to SB
292 if (next >= 'A' && next <= 'Z') {
293 decodedChar = (char) (next - 64);
295 throw new ReaderException("Invalid extended code 39 sequence: " + c + next);
299 // %A to %E map to control codes ESC to US
300 if (next >= 'A' && next <= 'E') {
301 decodedChar = (char) (next - 38);
302 } else if (next >= 'F' && next <= 'W') {
303 decodedChar = (char) (next - 11);
305 throw new ReaderException("Invalid extended code 39 sequence: " + c + next);
309 // /A to /O map to ! to , and /Z maps to :
310 if (next >= 'A' && next <= 'O') {
311 decodedChar = (char) (next - 32);
312 } else if (next == 'Z') {
315 throw new ReaderException("Invalid extended sequence: " + c + next);
319 decoded.append(decodedChar);
320 // bump up i again since we read two characters
326 return decoded.toString();