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)
33 * @author srowen@google.com (Sean Owen)
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 * 0.40625f);
39 private static final int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.5f);
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 static int[] findStartGuardPattern(BitArray row) throws ReaderException {
88 boolean foundStart = false;
89 int[] startRange = null;
92 startRange = findGuardPattern(row, nextStart, false, START_END_PATTERN);
93 int start = startRange[0];
94 nextStart = startRange[1];
95 // As a check, we want to see some white in front of this "start pattern",
96 // maybe as wide as the start pattern itself?
97 foundStart = row.isRange(Math.max(0, start - 2 * (startRange[1] - start)), start, false);
102 public final Result decodeRow(int rowNumber, BitArray row, Hashtable hints) throws ReaderException {
103 return decodeRow(rowNumber, row, findStartGuardPattern(row));
106 public final Result decodeRow(int rowNumber, BitArray row, int[] startGuardRange) throws ReaderException {
107 StringBuffer result = new StringBuffer(20);
108 int endStart = decodeMiddle(row, startGuardRange, result);
109 int[] endRange = decodeEnd(row, endStart);
111 // Check for whitespace after the pattern
112 int end = endRange[1];
113 if (!row.isRange(end, Math.min(row.getSize(), end + 2 * (end - endRange[0])), false)) {
114 throw new ReaderException("Pattern not followed by whitespace");
117 String resultString = result.toString();
118 if (!checkChecksum(resultString)) {
119 throw new ReaderException("Checksum failed");
122 float left = (float) (startGuardRange[1] + startGuardRange[0]) / 2.0f;
123 float right = (float) (endRange[1] + endRange[0]) / 2.0f;
124 return new Result(resultString,
125 null, // no natural byte representation for these barcodes
127 new GenericResultPoint(left, (float) rowNumber),
128 new GenericResultPoint(right, (float) rowNumber)},
132 abstract BarcodeFormat getBarcodeFormat();
135 * Computes the UPC/EAN checksum on a string of digits, and reports
136 * whether the checksum is correct or not.
138 * @param s string of digits to check
139 * @return true iff string of digits passes the UPC/EAN checksum algorithm
140 * @throws ReaderException if the string does not contain only digits
142 boolean checkChecksum(String s) throws ReaderException {
144 int length = s.length();
145 for (int i = length - 2; i >= 0; i -= 2) {
146 int digit = (int) s.charAt(i) - (int) '0';
147 if (digit < 0 || digit > 9) {
148 throw new ReaderException("Illegal character during checksum");
153 for (int i = length - 1; i >= 0; i -= 2) {
154 int digit = (int) s.charAt(i) - (int) '0';
155 if (digit < 0 || digit > 9) {
156 throw new ReaderException("Illegal character during checksum");
160 return sum % 10 == 0;
164 * Subclasses override this to decode the portion of a barcode between the start and end guard patterns.
166 * @param row row of black/white values to search
167 * @param startRange start/end offset of start guard pattern
168 * @param resultString {@link StringBuffer} to append decoded chars to
169 * @return horizontal offset of first pixel after the "middle" that was decoded
170 * @throws ReaderException if decoding could not complete successfully
172 protected abstract int decodeMiddle(BitArray row, int[] startRange, StringBuffer resultString)
173 throws ReaderException;
175 int[] decodeEnd(BitArray row, int endStart) throws ReaderException {
176 return findGuardPattern(row, endStart, false, START_END_PATTERN);
180 * @param row row of black/white values to search
181 * @param rowOffset position to start search
182 * @param whiteFirst if true, indicates that the pattern specifies white/black/white/...
183 * pixel counts, otherwise, it is interpreted as black/white/black/...
184 * @param pattern pattern of counts of number of black and white pixels that are being
185 * searched for as a pattern
186 * @return start/end horizontal offset of guard pattern, as an array of two ints
187 * @throws ReaderException if pattern is not found
189 static int[] findGuardPattern(BitArray row, int rowOffset, boolean whiteFirst, int[] pattern)
190 throws ReaderException {
191 int patternLength = pattern.length;
192 int[] counters = new int[patternLength];
193 int width = row.getSize();
194 boolean isWhite = false;
195 while (rowOffset < width) {
196 isWhite = !row.get(rowOffset);
197 if (whiteFirst == isWhite) {
203 int counterPosition = 0;
204 int patternStart = rowOffset;
205 for (int x = rowOffset; x < width; x++) {
206 boolean pixel = row.get(x);
207 if ((!pixel && isWhite) || (pixel && !isWhite)) {
208 counters[counterPosition]++;
210 if (counterPosition == patternLength - 1) {
211 if (patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE) {
212 return new int[]{patternStart, x};
214 patternStart += counters[0] + counters[1];
215 for (int y = 2; y < patternLength; y++) {
216 counters[y - 2] = counters[y];
218 counters[patternLength - 2] = 0;
219 counters[patternLength - 1] = 0;
224 counters[counterPosition] = 1;
228 throw new ReaderException("Can't find pattern");
232 * Attempts to decode a single UPC/EAN-encoded digit.
234 * @param row row of black/white values to decode
235 * @param counters the counts of runs of observed black/white/black/... values
236 * @param rowOffset horizontal offset to start decoding from
237 * @param patterns the set of patterns to use to decode -- sometimes different encodings
238 * for the digits 0-9 are used, and this indicates the encodings for 0 to 9 that should
240 * @return horizontal offset of first pixel beyond the decoded digit
241 * @throws ReaderException if digit cannot be decoded
243 static int decodeDigit(BitArray row, int[] counters, int rowOffset, int[][] patterns)
244 throws ReaderException {
245 recordPattern(row, rowOffset, counters);
246 int bestVariance = MAX_AVG_VARIANCE; // worst variance we'll accept
248 int max = patterns.length;
249 for (int i = 0; i < max; i++) {
250 int[] pattern = patterns[i];
251 int variance = patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE);
252 if (variance < bestVariance) {
253 bestVariance = variance;
257 if (bestMatch >= 0) {
260 throw new ReaderException("Could not match any digit in pattern");