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>Encapsulates functionality and implementation that is common to UPC and EAN families
30 * of one-dimensional barcodes.</p>
32 * @author dswitkin@google.com (Daniel Switkin)
34 * @author alasdair@google.com (Alasdair Mackintosh)
36 public abstract class AbstractUPCEANReader extends AbstractOneDReader implements UPCEANReader {
38 private static final int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.42f);
39 private static final int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.7f);
42 * Start/end guard pattern.
44 private static final int[] START_END_PATTERN = {1, 1, 1,};
47 * Pattern marking the middle of a UPC/EAN pattern, separating the two halves.
49 static final int[] MIDDLE_PATTERN = {1, 1, 1, 1, 1};
52 * "Odd", or "L" patterns used to encode UPC/EAN digits.
54 static final int[][] L_PATTERNS = {
68 * As above but also including the "even", or "G" patterns used to encode UPC/EAN digits.
70 static final int[][] L_AND_G_PATTERNS;
73 L_AND_G_PATTERNS = new int[20][];
74 for (int i = 0; i < 10; i++) {
75 L_AND_G_PATTERNS[i] = L_PATTERNS[i];
77 for (int i = 10; i < 20; i++) {
78 int[] widths = L_PATTERNS[i - 10];
79 int[] reversedWidths = new int[widths.length];
80 for (int j = 0; j < widths.length; j++) {
81 reversedWidths[j] = widths[widths.length - j - 1];
83 L_AND_G_PATTERNS[i] = reversedWidths;
87 private final StringBuffer decodeRowStringBuffer;
89 public AbstractUPCEANReader() {
90 decodeRowStringBuffer = new StringBuffer(20);
93 static int[] findStartGuardPattern(BitArray row) throws ReaderException {
94 boolean foundStart = false;
95 int[] startRange = null;
98 startRange = findGuardPattern(row, nextStart, false, START_END_PATTERN);
99 int start = startRange[0];
100 nextStart = startRange[1];
101 // Make sure there is a quiet zone at least as big as the start pattern before the barcode. If
102 // this check would run off the left edge of the image, do not accept this barcode, as it is
103 // very likely to be a false positive.
104 int quietStart = start - (nextStart - start);
105 if (quietStart >= 0) {
106 foundStart = row.isRange(quietStart, start, false);
112 public final Result decodeRow(int rowNumber, BitArray row, Hashtable hints) throws ReaderException {
113 return decodeRow(rowNumber, row, findStartGuardPattern(row));
116 public final Result decodeRow(int rowNumber, BitArray row, int[] startGuardRange) throws ReaderException {
117 StringBuffer result = decodeRowStringBuffer;
119 int endStart = decodeMiddle(row, startGuardRange, result);
120 int[] endRange = decodeEnd(row, endStart);
122 // Make sure there is a quiet zone at least as big as the end pattern after the barcode. The
123 // spec might want more whitespace, but in practice this is the maximum we can count on.
124 int end = endRange[1];
125 int quietEnd = end + (end - endRange[0]);
126 if (quietEnd >= row.getSize() || !row.isRange(end, quietEnd, false)) {
127 throw ReaderException.getInstance();
130 String resultString = result.toString();
131 if (!checkChecksum(resultString)) {
132 throw ReaderException.getInstance();
135 float left = (float) (startGuardRange[1] + startGuardRange[0]) / 2.0f;
136 float right = (float) (endRange[1] + endRange[0]) / 2.0f;
137 return new Result(resultString,
138 null, // no natural byte representation for these barcodes
140 new GenericResultPoint(left, (float) rowNumber),
141 new GenericResultPoint(right, (float) rowNumber)},
145 abstract BarcodeFormat getBarcodeFormat();
148 * Computes the UPC/EAN checksum on a string of digits, and reports
149 * whether the checksum is correct or not.
151 * @param s string of digits to check
152 * @return true iff string of digits passes the UPC/EAN checksum algorithm
153 * @throws ReaderException if the string does not contain only digits
155 boolean checkChecksum(String s) throws ReaderException {
156 int length = s.length();
162 for (int i = length - 2; i >= 0; i -= 2) {
163 int digit = (int) s.charAt(i) - (int) '0';
164 if (digit < 0 || digit > 9) {
165 throw ReaderException.getInstance();
170 for (int i = length - 1; i >= 0; i -= 2) {
171 int digit = (int) s.charAt(i) - (int) '0';
172 if (digit < 0 || digit > 9) {
173 throw ReaderException.getInstance();
177 return sum % 10 == 0;
181 * Subclasses override this to decode the portion of a barcode between the start and end guard patterns.
183 * @param row row of black/white values to search
184 * @param startRange start/end offset of start guard pattern
185 * @param resultString {@link StringBuffer} to append decoded chars to
186 * @return horizontal offset of first pixel after the "middle" that was decoded
187 * @throws ReaderException if decoding could not complete successfully
189 protected abstract int decodeMiddle(BitArray row, int[] startRange, StringBuffer resultString)
190 throws ReaderException;
192 int[] decodeEnd(BitArray row, int endStart) throws ReaderException {
193 return findGuardPattern(row, endStart, false, START_END_PATTERN);
197 * @param row row of black/white values to search
198 * @param rowOffset position to start search
199 * @param whiteFirst if true, indicates that the pattern specifies white/black/white/...
200 * pixel counts, otherwise, it is interpreted as black/white/black/...
201 * @param pattern pattern of counts of number of black and white pixels that are being
202 * searched for as a pattern
203 * @return start/end horizontal offset of guard pattern, as an array of two ints
204 * @throws ReaderException if pattern is not found
206 static int[] findGuardPattern(BitArray row, int rowOffset, boolean whiteFirst, int[] pattern)
207 throws ReaderException {
208 int patternLength = pattern.length;
209 int[] counters = new int[patternLength];
210 int width = row.getSize();
211 boolean isWhite = false;
212 while (rowOffset < width) {
213 isWhite = !row.get(rowOffset);
214 if (whiteFirst == isWhite) {
220 int counterPosition = 0;
221 int patternStart = rowOffset;
222 for (int x = rowOffset; x < width; x++) {
223 boolean pixel = row.get(x);
224 if ((!pixel && isWhite) || (pixel && !isWhite)) {
225 counters[counterPosition]++;
227 if (counterPosition == patternLength - 1) {
228 if (patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE) {
229 return new int[]{patternStart, x};
231 patternStart += counters[0] + counters[1];
232 for (int y = 2; y < patternLength; y++) {
233 counters[y - 2] = counters[y];
235 counters[patternLength - 2] = 0;
236 counters[patternLength - 1] = 0;
241 counters[counterPosition] = 1;
245 throw ReaderException.getInstance();
249 * Attempts to decode a single UPC/EAN-encoded digit.
251 * @param row row of black/white values to decode
252 * @param counters the counts of runs of observed black/white/black/... values
253 * @param rowOffset horizontal offset to start decoding from
254 * @param patterns the set of patterns to use to decode -- sometimes different encodings
255 * for the digits 0-9 are used, and this indicates the encodings for 0 to 9 that should
257 * @return horizontal offset of first pixel beyond the decoded digit
258 * @throws ReaderException if digit cannot be decoded
260 static int decodeDigit(BitArray row, int[] counters, int rowOffset, int[][] patterns)
261 throws ReaderException {
262 recordPattern(row, rowOffset, counters);
263 int bestVariance = MAX_AVG_VARIANCE; // worst variance we'll accept
265 int max = patterns.length;
266 for (int i = 0; i < max; i++) {
267 int[] pattern = patterns[i];
268 int variance = patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE);
269 if (variance < bestVariance) {
270 bestVariance = variance;
274 if (bestMatch >= 0) {
277 throw ReaderException.getInstance();