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.ChecksumException;
21 import com.google.zxing.DecodeHintType;
22 import com.google.zxing.FormatException;
23 import com.google.zxing.NotFoundException;
24 import com.google.zxing.ReaderException;
25 import com.google.zxing.Result;
26 import com.google.zxing.ResultPoint;
27 import com.google.zxing.ResultPointCallback;
28 import com.google.zxing.common.BitArray;
30 import java.util.Hashtable;
33 * <p>Encapsulates functionality and implementation that is common to UPC and EAN families
34 * of one-dimensional barcodes.</p>
36 * @author dswitkin@google.com (Daniel Switkin)
38 * @author alasdair@google.com (Alasdair Mackintosh)
40 public abstract class UPCEANReader extends OneDReader {
42 // These two values are critical for determining how permissive the decoding will be.
43 // We've arrived at these values through a lot of trial and error. Setting them any higher
44 // lets false positives creep in quickly.
45 private static final int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.42f);
46 private static final int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.7f);
49 * Start/end guard pattern.
51 static final int[] START_END_PATTERN = {1, 1, 1,};
54 * Pattern marking the middle of a UPC/EAN pattern, separating the two halves.
56 static final int[] MIDDLE_PATTERN = {1, 1, 1, 1, 1};
59 * "Odd", or "L" patterns used to encode UPC/EAN digits.
61 static final int[][] L_PATTERNS = {
75 * As above but also including the "even", or "G" patterns used to encode UPC/EAN digits.
77 static final int[][] L_AND_G_PATTERNS;
80 L_AND_G_PATTERNS = new int[20][];
81 for (int i = 0; i < 10; i++) {
82 L_AND_G_PATTERNS[i] = L_PATTERNS[i];
84 for (int i = 10; i < 20; i++) {
85 int[] widths = L_PATTERNS[i - 10];
86 int[] reversedWidths = new int[widths.length];
87 for (int j = 0; j < widths.length; j++) {
88 reversedWidths[j] = widths[widths.length - j - 1];
90 L_AND_G_PATTERNS[i] = reversedWidths;
94 private final StringBuffer decodeRowStringBuffer;
95 private final UPCEANExtensionSupport extensionReader;
97 protected UPCEANReader() {
98 decodeRowStringBuffer = new StringBuffer(20);
99 extensionReader = new UPCEANExtensionSupport();
102 static int[] findStartGuardPattern(BitArray row) throws NotFoundException {
103 boolean foundStart = false;
104 int[] startRange = null;
106 while (!foundStart) {
107 startRange = findGuardPattern(row, nextStart, false, START_END_PATTERN);
108 int start = startRange[0];
109 nextStart = startRange[1];
110 // Make sure there is a quiet zone at least as big as the start pattern before the barcode.
111 // If this check would run off the left edge of the image, do not accept this barcode,
112 // as it is very likely to be a false positive.
113 int quietStart = start - (nextStart - start);
114 if (quietStart >= 0) {
115 foundStart = row.isRange(quietStart, start, false);
121 public Result decodeRow(int rowNumber, BitArray row, Hashtable hints)
122 throws NotFoundException, ChecksumException, FormatException {
123 return decodeRow(rowNumber, row, findStartGuardPattern(row), hints);
127 * <p>Like {@link #decodeRow(int, BitArray, java.util.Hashtable)}, but
128 * allows caller to inform method about where the UPC/EAN start pattern is
129 * found. This allows this to be computed once and reused across many implementations.</p>
131 public Result decodeRow(int rowNumber, BitArray row, int[] startGuardRange, Hashtable hints)
132 throws NotFoundException, ChecksumException, FormatException {
134 ResultPointCallback resultPointCallback = hints == null ? null :
135 (ResultPointCallback) hints.get(DecodeHintType.NEED_RESULT_POINT_CALLBACK);
137 if (resultPointCallback != null) {
138 resultPointCallback.foundPossibleResultPoint(new ResultPoint(
139 (startGuardRange[0] + startGuardRange[1]) / 2.0f, rowNumber
143 StringBuffer result = decodeRowStringBuffer;
145 int endStart = decodeMiddle(row, startGuardRange, result);
147 if (resultPointCallback != null) {
148 resultPointCallback.foundPossibleResultPoint(new ResultPoint(
153 int[] endRange = decodeEnd(row, endStart);
155 if (resultPointCallback != null) {
156 resultPointCallback.foundPossibleResultPoint(new ResultPoint(
157 (endRange[0] + endRange[1]) / 2.0f, rowNumber
162 // Make sure there is a quiet zone at least as big as the end pattern after the barcode. The
163 // spec might want more whitespace, but in practice this is the maximum we can count on.
164 int end = endRange[1];
165 int quietEnd = end + (end - endRange[0]);
166 if (quietEnd >= row.getSize() || !row.isRange(end, quietEnd, false)) {
167 throw NotFoundException.getNotFoundInstance();
170 String resultString = result.toString();
171 if (!checkChecksum(resultString)) {
172 throw ChecksumException.getChecksumInstance();
175 float left = (float) (startGuardRange[1] + startGuardRange[0]) / 2.0f;
176 float right = (float) (endRange[1] + endRange[0]) / 2.0f;
177 Result decodeResult = new Result(resultString,
178 null, // no natural byte representation for these barcodes
180 new ResultPoint(left, (float) rowNumber),
181 new ResultPoint(right, (float) rowNumber)},
185 Result extensionResult = extensionReader.decodeRow(row, endRange[1]);
186 decodeResult.putAllMetadata(extensionResult.getResultMetadata());
187 } catch (ReaderException re) {
194 * @return {@link #checkStandardUPCEANChecksum(String)}
196 boolean checkChecksum(String s) throws ChecksumException, FormatException {
197 return checkStandardUPCEANChecksum(s);
201 * Computes the UPC/EAN checksum on a string of digits, and reports
202 * whether the checksum is correct or not.
204 * @param s string of digits to check
205 * @return true iff string of digits passes the UPC/EAN checksum algorithm
206 * @throws FormatException if the string does not contain only digits
208 private static boolean checkStandardUPCEANChecksum(String s) throws FormatException {
209 int length = s.length();
215 for (int i = length - 2; i >= 0; i -= 2) {
216 int digit = (int) s.charAt(i) - (int) '0';
217 if (digit < 0 || digit > 9) {
218 throw FormatException.getFormatInstance();
223 for (int i = length - 1; i >= 0; i -= 2) {
224 int digit = (int) s.charAt(i) - (int) '0';
225 if (digit < 0 || digit > 9) {
226 throw FormatException.getFormatInstance();
230 return sum % 10 == 0;
233 int[] decodeEnd(BitArray row, int endStart) throws NotFoundException {
234 return findGuardPattern(row, endStart, false, START_END_PATTERN);
238 * @param row row of black/white values to search
239 * @param rowOffset position to start search
240 * @param whiteFirst if true, indicates that the pattern specifies white/black/white/...
241 * pixel counts, otherwise, it is interpreted as black/white/black/...
242 * @param pattern pattern of counts of number of black and white pixels that are being
243 * searched for as a pattern
244 * @return start/end horizontal offset of guard pattern, as an array of two ints
245 * @throws NotFoundException if pattern is not found
247 static int[] findGuardPattern(BitArray row, int rowOffset, boolean whiteFirst, int[] pattern)
248 throws NotFoundException {
249 int patternLength = pattern.length;
250 int[] counters = new int[patternLength];
251 int width = row.getSize();
252 boolean isWhite = false;
253 while (rowOffset < width) {
254 isWhite = !row.get(rowOffset);
255 if (whiteFirst == isWhite) {
261 int counterPosition = 0;
262 int patternStart = rowOffset;
263 for (int x = rowOffset; x < width; x++) {
264 boolean pixel = row.get(x);
265 if (pixel ^ isWhite) {
266 counters[counterPosition]++;
268 if (counterPosition == patternLength - 1) {
269 if (patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE) {
270 return new int[]{patternStart, x};
272 patternStart += counters[0] + counters[1];
273 for (int y = 2; y < patternLength; y++) {
274 counters[y - 2] = counters[y];
276 counters[patternLength - 2] = 0;
277 counters[patternLength - 1] = 0;
282 counters[counterPosition] = 1;
286 throw NotFoundException.getNotFoundInstance();
290 * Attempts to decode a single UPC/EAN-encoded digit.
292 * @param row row of black/white values to decode
293 * @param counters the counts of runs of observed black/white/black/... values
294 * @param rowOffset horizontal offset to start decoding from
295 * @param patterns the set of patterns to use to decode -- sometimes different encodings
296 * for the digits 0-9 are used, and this indicates the encodings for 0 to 9 that should
298 * @return horizontal offset of first pixel beyond the decoded digit
299 * @throws NotFoundException if digit cannot be decoded
301 static int decodeDigit(BitArray row, int[] counters, int rowOffset, int[][] patterns)
302 throws NotFoundException {
303 recordPattern(row, rowOffset, counters);
304 int bestVariance = MAX_AVG_VARIANCE; // worst variance we'll accept
306 int max = patterns.length;
307 for (int i = 0; i < max; i++) {
308 int[] pattern = patterns[i];
309 int variance = patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE);
310 if (variance < bestVariance) {
311 bestVariance = variance;
315 if (bestMatch >= 0) {
318 throw NotFoundException.getNotFoundInstance();
323 * Get the format of this decoder.
325 * @return The 1D format.
327 abstract BarcodeFormat getBarcodeFormat();
330 * Subclasses override this to decode the portion of a barcode between the start
331 * and end guard patterns.
333 * @param row row of black/white values to search
334 * @param startRange start/end offset of start guard pattern
335 * @param resultString {@link StringBuffer} to append decoded chars to
336 * @return horizontal offset of first pixel after the "middle" that was decoded
337 * @throws NotFoundException if decoding could not complete successfully
339 protected abstract int decodeMiddle(BitArray row, int[] startRange, StringBuffer resultString)
340 throws NotFoundException;