2 * Copyright 2008 ZXing authors
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4 * Licensed under the Apache License, Version 2.0 (the "License");
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5 * you may not use this file except in compliance with the License.
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6 * You may obtain a copy of the License at
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8 * http://www.apache.org/licenses/LICENSE-2.0
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10 * Unless required by applicable law or agreed to in writing, software
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11 * distributed under the License is distributed on an "AS IS" BASIS,
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12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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13 * See the License for the specific language governing permissions and
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14 * limitations under the License.
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17 package com.google.zxing.oned;
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19 import com.google.zxing.BarcodeFormat;
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20 import com.google.zxing.ReaderException;
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21 import com.google.zxing.Result;
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22 import com.google.zxing.ResultPoint;
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23 import com.google.zxing.DecodeHintType;
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24 import com.google.zxing.common.BitArray;
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25 import com.google.zxing.common.GenericResultPoint;
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27 import java.util.Hashtable;
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30 * <p>Implements decoding of the ITF format.</p>
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32 * <p>"ITF" stands for Interleaved Two of Five. This Reader will scan ITF barcode with 6, 10 or 14 digits.
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33 * The checksum is optional and is not applied by this Reader. The consumer of the decoded value
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34 * will have to apply a checksum if required.</p>
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36 * <p><a href="http://en.wikipedia.org/wiki/Interleaved_2_of_5">http://en.wikipedia.org/wiki/Interleaved_2_of_5</a>
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37 * is a great reference for Interleaved 2 of 5 information.</p>
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39 * @author kevin.osullivan@sita.aero, SITA Lab.
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41 public final class ITFReader extends AbstractOneDReader {
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43 private static final int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.42f);
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44 private static final int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.8f);
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46 private static final int W = 3; // Pixel width of a wide line
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47 private static final int N = 1; // Pixed width of a narrow line
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49 private static final int[] DEFAULT_ALLOWED_LENGTHS = { 6, 10, 14 };
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51 // Stores the actual narrow line width of the image being decoded.
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52 private int narrowLineWidth = -1;
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55 * Start/end guard pattern.
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57 * Note: The end pattern is reversed because the row is reversed before
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58 * searching for the END_PATTERN
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60 private static final int[] START_PATTERN = {N, N, N, N};
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61 private static final int[] END_PATTERN_REVERSED = {N, N, W};
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64 * Patterns of Wide / Narrow lines to indicate each digit
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66 private static final int[][] PATTERNS = {
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67 {N, N, W, W, N}, // 0
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68 {W, N, N, N, W}, // 1
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69 {N, W, N, N, W}, // 2
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70 {W, W, N, N, N}, // 3
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71 {N, N, W, N, W}, // 4
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72 {W, N, W, N, N}, // 5
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73 {N, W, W, N, N}, // 6
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74 {N, N, N, W, W}, // 7
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75 {W, N, N, W, N}, // 8
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76 {N, W, N, W, N} // 9
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79 public Result decodeRow(int rowNumber, BitArray row, Hashtable hints) throws ReaderException {
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81 StringBuffer result = new StringBuffer(20);
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83 // Find out where the Middle section (payload) starts & ends
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84 int[] startRange = decodeStart(row);
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85 int[] endRange = decodeEnd(row);
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87 decodeMiddle(row, startRange[1], endRange[0], result);
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89 String resultString = result.toString();
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91 int[] allowedLengths = null;
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92 if (hints != null) {
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93 allowedLengths = (int[]) hints.get(DecodeHintType.ALLOWED_LENGTHS);
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96 if (allowedLengths == null) {
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97 allowedLengths = DEFAULT_ALLOWED_LENGTHS;
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100 // To avoid false positives with 2D barcodes (and other patterns), make
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101 // an assumption that the decoded string must be 6, 10 or 14 digits.
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102 int length = resultString.length();
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103 boolean lengthOK = false;
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104 for (int i = 0; i < allowedLengths.length; i++) {
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105 if (length == allowedLengths[i]) {
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112 throw ReaderException.getInstance();
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117 null, // no natural byte representation for these barcodes
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118 new ResultPoint[] { new GenericResultPoint(startRange[1], (float) rowNumber),
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119 new GenericResultPoint(endRange[0], (float) rowNumber)},
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120 BarcodeFormat.ITF);
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124 * @param row row of black/white values to search
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125 * @param payloadStart offset of start pattern
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126 * @param resultString {@link StringBuffer} to append decoded chars to
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127 * @throws ReaderException if decoding could not complete successfully
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129 static void decodeMiddle(BitArray row, int payloadStart, int payloadEnd, StringBuffer resultString) throws ReaderException {
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131 // Digits are interleaved in pairs - 5 black lines for one digit, and the
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133 // interleaved white lines for the second digit.
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134 // Therefore, need to scan 10 lines and then
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135 // split these into two arrays
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136 int[] counterDigitPair = new int[10];
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137 int[] counterBlack = new int[5];
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138 int[] counterWhite = new int[5];
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140 while (payloadStart < payloadEnd) {
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142 // Get 10 runs of black/white.
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143 recordPattern(row, payloadStart, counterDigitPair);
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144 // Split them into each array
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145 for (int k = 0; k < 5; k++) {
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147 counterBlack[k] = counterDigitPair[twoK];
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148 counterWhite[k] = counterDigitPair[twoK + 1];
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151 int bestMatch = decodeDigit(counterBlack);
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152 resultString.append((char) ('0' + bestMatch));
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153 bestMatch = decodeDigit(counterWhite);
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154 resultString.append((char) ('0' + bestMatch));
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156 for (int i = 0; i < counterDigitPair.length; i++) {
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157 payloadStart += counterDigitPair[i];
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163 * Identify where the start of the middle / payload section starts.
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165 * @param row row of black/white values to search
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166 * @return Array, containing index of start of 'start block' and end of
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168 * @throws ReaderException
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170 int[] decodeStart(BitArray row) throws ReaderException {
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171 int endStart = skipWhiteSpace(row);
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172 int[] startPattern = findGuardPattern(row, endStart, START_PATTERN);
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174 // Determine the width of a narrow line in pixels. We can do this by
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175 // getting the width of the start pattern and dividing by 4 because its
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176 // made up of 4 narrow lines.
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177 this.narrowLineWidth = (startPattern[1] - startPattern[0]) >> 2;
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179 validateQuietZone(row, startPattern[0]);
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181 return startPattern;
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185 * The start & end patterns must be pre/post fixed by a quiet zone. This
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186 * zone must be at least 10 times the width of a narrow line. Scan back until
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187 * we either get to the start of the barcode or match the necessary number of
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188 * quiet zone pixels.
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190 * Note: Its assumed the row is reversed when using this method to find
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191 * quiet zone after the end pattern.
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193 * ref: http://www.barcode-1.net/i25code.html
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195 * @param row bit array representing the scanned barcode.
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196 * @param startPattern index into row of the start or end pattern.
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197 * @throws ReaderException if the quiet zone cannot be found, a ReaderException is thrown.
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199 private void validateQuietZone(BitArray row, int startPattern) throws ReaderException {
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201 int quietCount = this.narrowLineWidth * 10; // expect to find this many pixels of quiet zone
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203 for (int i = startPattern - 1; quietCount > 0 && i >= 0; i--) {
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209 if (quietCount != 0) {
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210 // Unable to find the necessary number of quiet zone pixels.
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211 throw ReaderException.getInstance();
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216 * Skip all whitespace until we get to the first black line.
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218 * @param row row of black/white values to search
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219 * @return index of the first black line.
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220 * @throws ReaderException Throws exception if no black lines are found in the row
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222 private static int skipWhiteSpace(BitArray row) throws ReaderException {
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223 int width = row.getSize();
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225 while (endStart < width) {
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226 if (row.get(endStart)) {
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231 if (endStart == width) {
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232 throw ReaderException.getInstance();
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239 * Identify where the end of the middle / payload section ends.
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241 * @param row row of black/white values to search
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242 * @return Array, containing index of start of 'end block' and end of 'end
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244 * @throws ReaderException
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247 int[] decodeEnd(BitArray row) throws ReaderException {
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249 // For convenience, reverse the row and then
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250 // search from 'the start' for the end block
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253 int endStart = skipWhiteSpace(row);
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254 int[] endPattern = findGuardPattern(row, endStart, END_PATTERN_REVERSED);
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256 // The start & end patterns must be pre/post fixed by a quiet zone. This
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257 // zone must be at least 10 times the width of a narrow line.
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258 // ref: http://www.barcode-1.net/i25code.html
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259 validateQuietZone(row, endPattern[0]);
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261 // Now recalc the indicies of where the 'endblock' starts & stops to
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263 // the reversed nature of the search
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264 int temp = endPattern[0];
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265 endPattern[0] = row.getSize() - endPattern[1];
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266 endPattern[1] = row.getSize() - temp;
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270 // Put the row back the righ way.
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276 * @param row row of black/white values to search
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277 * @param rowOffset position to start search
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278 * @param pattern pattern of counts of number of black and white pixels that are
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279 * being searched for as a pattern
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280 * @return start/end horizontal offset of guard pattern, as an array of two
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282 * @throws ReaderException if pattern is not found
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284 static int[] findGuardPattern(BitArray row, int rowOffset, int[] pattern) throws ReaderException {
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286 // TODO: This is very similar to implementation in AbstractUPCEANReader. Consider if they can be merged to
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287 // a single method.
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289 int patternLength = pattern.length;
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290 int[] counters = new int[patternLength];
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291 int width = row.getSize();
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292 boolean isWhite = false;
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294 int counterPosition = 0;
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295 int patternStart = rowOffset;
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296 for (int x = rowOffset; x < width; x++) {
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297 boolean pixel = row.get(x);
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298 if (pixel ^ isWhite) {
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299 counters[counterPosition]++;
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301 if (counterPosition == patternLength - 1) {
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302 if (patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE) {
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303 return new int[]{patternStart, x};
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305 patternStart += counters[0] + counters[1];
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306 for (int y = 2; y < patternLength; y++) {
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307 counters[y - 2] = counters[y];
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309 counters[patternLength - 2] = 0;
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310 counters[patternLength - 1] = 0;
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315 counters[counterPosition] = 1;
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316 isWhite ^= true; // isWhite = !isWhite;
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319 throw ReaderException.getInstance();
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323 * Attempts to decode a sequence of ITF black/white lines into single
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326 * @param counters the counts of runs of observed black/white/black/... values
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327 * @return The decoded digit
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328 * @throws ReaderException if digit cannot be decoded
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330 private static int decodeDigit(int[] counters) throws ReaderException {
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332 int bestVariance = MAX_AVG_VARIANCE; // worst variance we'll accept
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333 int bestMatch = -1;
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334 int max = PATTERNS.length;
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335 for (int i = 0; i < max; i++) {
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336 int[] pattern = PATTERNS[i];
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337 int variance = patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE);
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338 if (variance < bestVariance) {
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339 bestVariance = variance;
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343 if (bestMatch >= 0) {
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346 throw ReaderException.getInstance();
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