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 * 0.7f);
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 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 {
143 int length = s.length();
149 for (int i = length - 2; i >= 0; i -= 2) {
150 int digit = (int) s.charAt(i) - (int) '0';
151 if (digit < 0 || digit > 9) {
152 throw new ReaderException("Illegal character during checksum");
157 for (int i = length - 1; i >= 0; i -= 2) {
158 int digit = (int) s.charAt(i) - (int) '0';
159 if (digit < 0 || digit > 9) {
160 throw new ReaderException("Illegal character during checksum");
164 return sum % 10 == 0;
168 * Subclasses override this to decode the portion of a barcode between the start and end guard patterns.
170 * @param row row of black/white values to search
171 * @param startRange start/end offset of start guard pattern
172 * @param resultString {@link StringBuffer} to append decoded chars to
173 * @return horizontal offset of first pixel after the "middle" that was decoded
174 * @throws ReaderException if decoding could not complete successfully
176 protected abstract int decodeMiddle(BitArray row, int[] startRange, StringBuffer resultString)
177 throws ReaderException;
179 int[] decodeEnd(BitArray row, int endStart) throws ReaderException {
180 return findGuardPattern(row, endStart, false, START_END_PATTERN);
184 * @param row row of black/white values to search
185 * @param rowOffset position to start search
186 * @param whiteFirst if true, indicates that the pattern specifies white/black/white/...
187 * pixel counts, otherwise, it is interpreted as black/white/black/...
188 * @param pattern pattern of counts of number of black and white pixels that are being
189 * searched for as a pattern
190 * @return start/end horizontal offset of guard pattern, as an array of two ints
191 * @throws ReaderException if pattern is not found
193 static int[] findGuardPattern(BitArray row, int rowOffset, boolean whiteFirst, int[] pattern)
194 throws ReaderException {
195 int patternLength = pattern.length;
196 int[] counters = new int[patternLength];
197 int width = row.getSize();
198 boolean isWhite = false;
199 while (rowOffset < width) {
200 isWhite = !row.get(rowOffset);
201 if (whiteFirst == isWhite) {
207 int counterPosition = 0;
208 int patternStart = rowOffset;
209 for (int x = rowOffset; x < width; x++) {
210 boolean pixel = row.get(x);
211 if ((!pixel && isWhite) || (pixel && !isWhite)) {
212 counters[counterPosition]++;
214 if (counterPosition == patternLength - 1) {
215 if (patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE) {
216 return new int[]{patternStart, x};
218 patternStart += counters[0] + counters[1];
219 for (int y = 2; y < patternLength; y++) {
220 counters[y - 2] = counters[y];
222 counters[patternLength - 2] = 0;
223 counters[patternLength - 1] = 0;
228 counters[counterPosition] = 1;
232 throw new ReaderException("Can't find pattern");
236 * Attempts to decode a single UPC/EAN-encoded digit.
238 * @param row row of black/white values to decode
239 * @param counters the counts of runs of observed black/white/black/... values
240 * @param rowOffset horizontal offset to start decoding from
241 * @param patterns the set of patterns to use to decode -- sometimes different encodings
242 * for the digits 0-9 are used, and this indicates the encodings for 0 to 9 that should
244 * @return horizontal offset of first pixel beyond the decoded digit
245 * @throws ReaderException if digit cannot be decoded
247 static int decodeDigit(BitArray row, int[] counters, int rowOffset, int[][] patterns)
248 throws ReaderException {
249 recordPattern(row, rowOffset, counters);
250 int bestVariance = MAX_AVG_VARIANCE; // worst variance we'll accept
252 int max = patterns.length;
253 for (int i = 0; i < max; i++) {
254 int[] pattern = patterns[i];
255 int variance = patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE);
256 if (variance < bestVariance) {
257 bestVariance = variance;
261 if (bestMatch >= 0) {
264 throw new ReaderException("Could not match any digit in pattern");