ITFReader.cpp Example File

 // -*- mode:c++; tab-width:2; indent-tabs-mode:nil; c-basic-offset:2 -*-
 /*
  *  Copyright 2010 ZXing authors All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include <zxing/ZXing.h>
 #include <zxing/oned/ITFReader.h>
 #include <zxing/oned/OneDResultPoint.h>
 #include <zxing/common/Array.h>
 #include <zxing/ReaderException.h>
 #include <zxing/FormatException.h>
 #include <zxing/NotFoundException.h>
 #include <math.h>

 using std::vector;
 using zxing::Ref;
 using zxing::ArrayRef;
 using zxing::Array;
 using zxing::Result;
 using zxing::FormatException;
 using zxing::NotFoundException;
 using zxing::oned::ITFReader;

 // VC++
 using zxing::BitArray;

 #define VECTOR_INIT(v) v, v + sizeof(v)/sizeof(v[0])

 namespace {

 const int W = 3; // Pixel width of a wide line
 const int N = 1; // Pixed width of a narrow line

 const int DEFAULT_ALLOWED_LENGTHS_[] =
 { 48, 44, 24, 20, 18, 16, 14, 12, 10, 8, 6 };
 const ArrayRef<int> DEFAULT_ALLOWED_LENGTHS (new Array<int>(VECTOR_INIT(DEFAULT_ALLOWED_LENGTHS_)));

 /**
  * Start/end guard pattern.
  *
  * Note: The end pattern is reversed because the row is reversed before
  * searching for the END_PATTERN
  */
 const int START_PATTERN_[] = {N, N, N, N};
 const vector<int> START_PATTERN (VECTOR_INIT(START_PATTERN_));

 const int END_PATTERN_REVERSED_[] = {N, N, W};
 const vector<int> END_PATTERN_REVERSED (VECTOR_INIT(END_PATTERN_REVERSED_));

 /**
  * Patterns of Wide / Narrow lines to indicate each digit
  */
 const int PATTERNS[][5] = {
   {N, N, W, W, N}, // 0
   {W, N, N, N, W}, // 1
   {N, W, N, N, W}, // 2
   {W, W, N, N, N}, // 3
   {N, N, W, N, W}, // 4
   {W, N, W, N, N}, // 5
   {N, W, W, N, N}, // 6
   {N, N, N, W, W}, // 7
   {W, N, N, W, N}, // 8
   {N, W, N, W, N}  // 9
 };

 }

 ITFReader::ITFReader() : narrowLineWidth(-1) {
 }

 Ref<Result> ITFReader::decodeRow(int rowNumber, Ref<BitArray> row, zxing::DecodeHints /*hints*/) {
   // Find out where the Middle section (payload) starts & ends

   Range startRange = decodeStart(row);
   Range endRange = decodeEnd(row);

   std::string result;
   decodeMiddle(row, startRange[1], endRange[0], result);
   Ref<String> resultString(new String(result));

   ArrayRef<int> allowedLengths;
   // Java hints stuff missing
   if (!allowedLengths) {
     allowedLengths = DEFAULT_ALLOWED_LENGTHS;
   }

   // To avoid false positives with 2D barcodes (and other patterns), make
   // an assumption that the decoded string must be 6, 10 or 14 digits.
   int length = resultString->size();
   bool lengthOK = false;
   for (int i = 0, e = allowedLengths->size(); i < e; i++) {
     if (length == allowedLengths[i]) {
       lengthOK = true;
       break;
     }
   }

   if (!lengthOK) {
     throw FormatException();
   }

   ArrayRef< Ref<ResultPoint> > resultPoints(2);
   resultPoints[0] =
       Ref<OneDResultPoint>(new OneDResultPoint(float(startRange[1]), float(rowNumber)));
   resultPoints[1] =
       Ref<OneDResultPoint>(new OneDResultPoint(float(endRange[0]), float(rowNumber)));
   return Ref<Result>(new Result(resultString, ArrayRef<byte>(), resultPoints, BarcodeFormat::ITF));
 }

 /**
  * @param row          row of black/white values to search
  * @param payloadStart offset of start pattern
  * @param resultString {@link StringBuffer} to append decoded chars to
  * @throws ReaderException if decoding could not complete successfully
  */
 void ITFReader::decodeMiddle(Ref<BitArray> row,
                              int payloadStart,
                              int payloadEnd,
                              std::string& resultString) {
   // Digits are interleaved in pairs - 5 black lines for one digit, and the
   // 5
   // interleaved white lines for the second digit.
   // Therefore, need to scan 10 lines and then
   // split these into two arrays
   vector<int> counterDigitPair(10, 0);
   vector<int> counterBlack(5, 0);
   vector<int> counterWhite(5, 0);

   while (payloadStart < payloadEnd) {

     // Get 10 runs of black/white.
     recordPattern(row, payloadStart, counterDigitPair);
     // Split them into each array
     for (int k = 0; k < 5; k++) {
       int twoK = k << 1;
       counterBlack[k] = counterDigitPair[twoK];
       counterWhite[k] = counterDigitPair[twoK + 1];
     }

     int bestMatch = decodeDigit(counterBlack);
     resultString.append(1, (byte) ('0' + bestMatch));
     bestMatch = decodeDigit(counterWhite);
     resultString.append(1, (byte) ('0' + bestMatch));

     for (int i = 0, e = counterDigitPair.size(); i < e; i++) {
       payloadStart += counterDigitPair[i];
     }
   }
 }

 /**
  * Identify where the start of the middle / payload section starts.
  *
  * @param row row of black/white values to search
  * @return Array, containing index of start of 'start block' and end of
  *         'start block'
  * @throws ReaderException
  */
 ITFReader::Range ITFReader::decodeStart(Ref<BitArray> row) {
   int endStart = skipWhiteSpace(row);
   Range startPattern = findGuardPattern(row, endStart, START_PATTERN);

   // Determine the width of a narrow line in pixels. We can do this by
   // getting the width of the start pattern and dividing by 4 because its
   // made up of 4 narrow lines.
   narrowLineWidth = (startPattern[1] - startPattern[0]) >> 2;

   validateQuietZone(row, startPattern[0]);
   return startPattern;
 }

 /**
  * Identify where the end of the middle / payload section ends.
  *
  * @param row row of black/white values to search
  * @return Array, containing index of start of 'end block' and end of 'end
  *         block'
  * @throws ReaderException
  */

 ITFReader::Range ITFReader::decodeEnd(Ref<BitArray> row) {
   // For convenience, reverse the row and then
   // search from 'the start' for the end block
   BitArray::Reverse r (row);

   int endStart = skipWhiteSpace(row);
   Range endPattern = findGuardPattern(row, endStart, END_PATTERN_REVERSED);

   // The start & end patterns must be pre/post fixed by a quiet zone. This
   // zone must be at least 10 times the width of a narrow line.
   // ref: http://www.barcode-1.net/i25code.html
   validateQuietZone(row, endPattern[0]);

   // Now recalculate the indices of where the 'endblock' starts & stops to
   // accommodate
   // the reversed nature of the search
   int temp = endPattern[0];
   endPattern[0] = row->getSize() - endPattern[1];
   endPattern[1] = row->getSize() - temp;

   return endPattern;
 }

 /**
  * The start & end patterns must be pre/post fixed by a quiet zone. This
  * zone must be at least 10 times the width of a narrow line.  Scan back until
  * we either get to the start of the barcode or match the necessary number of
  * quiet zone pixels.
  *
  * Note: Its assumed the row is reversed when using this method to find
  * quiet zone after the end pattern.
  *
  * ref: http://www.barcode-1.net/i25code.html
  *
  * @param row bit array representing the scanned barcode.
  * @param startPattern index into row of the start or end pattern.
  * @throws ReaderException if the quiet zone cannot be found, a ReaderException is thrown.
  */
 void ITFReader::validateQuietZone(Ref<BitArray> row, int startPattern) {
   int quietCount = this->narrowLineWidth * 10;  // expect to find this many pixels of quiet zone

   for (int i = startPattern - 1; quietCount > 0 && i >= 0; i--) {
     if (row->get(i)) {
       break;
     }
     quietCount--;
   }
   if (quietCount != 0) {
     // Unable to find the necessary number of quiet zone pixels.
     throw NotFoundException();
   }
 }

 /**
  * Skip all whitespace until we get to the first black line.
  *
  * @param row row of black/white values to search
  * @return index of the first black line.
  * @throws ReaderException Throws exception if no black lines are found in the row
  */
 int ITFReader::skipWhiteSpace(Ref<BitArray> row) {
   int width = row->getSize();
   int endStart = row->getNextSet(0);
   if (endStart == width) {
     throw NotFoundException();
   }
   return endStart;
 }

 /**
  * @param row       row of black/white values to search
  * @param rowOffset position to start search
  * @param pattern   pattern of counts of number of black and white pixels that are
  *                  being searched for as a pattern
  * @return start/end horizontal offset of guard pattern, as an array of two
  *         ints
  * @throws ReaderException if pattern is not found
  */
 ITFReader::Range ITFReader::findGuardPattern(Ref<BitArray> row,
                                              int rowOffset,
                                              vector<int> const& pattern) {
   // TODO: This is very similar to implementation in UPCEANReader. Consider if they can be
   // merged to a single method.
   int patternLength = pattern.size();
   vector<int> counters(patternLength);
   int width = row->getSize();
   bool isWhite = false;

   int counterPosition = 0;
   int patternStart = rowOffset;
   for (int x = rowOffset; x < width; x++) {
     if (row->get(x) ^ isWhite) {
       counters[counterPosition]++;
     } else {
       if (counterPosition == patternLength - 1) {
         if (patternMatchVariance(counters, &pattern[0], MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE) {
           return Range(patternStart, x);
         }
         patternStart += counters[0] + counters[1];
         for (int y = 2; y < patternLength; y++) {
           counters[y - 2] = counters[y];
         }
         counters[patternLength - 2] = 0;
         counters[patternLength - 1] = 0;
         counterPosition--;
       } else {
         counterPosition++;
       }
       counters[counterPosition] = 1;
       isWhite = !isWhite;
     }
   }
   throw NotFoundException();
 }

 /**
  * Attempts to decode a sequence of ITF black/white lines into single
  * digit.
  *
  * @param counters the counts of runs of observed black/white/black/... values
  * @return The decoded digit
  * @throws ReaderException if digit cannot be decoded
  */
 int ITFReader::decodeDigit(vector<int>& counters){

   int bestVariance = MAX_AVG_VARIANCE; // worst variance we'll accept
   int bestMatch = -1;
   int max = sizeof(PATTERNS)/sizeof(PATTERNS[0]);
   for (int i = 0; i < max; i++) {
     int const* pattern = PATTERNS[i];
     int variance = patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE);
     if (variance < bestVariance) {
       bestVariance = variance;
       bestMatch = i;
     }
   }
   if (bestMatch >= 0) {
     return bestMatch;
   } else {
     throw NotFoundException();
   }
 }

 ITFReader::~ITFReader(){}