zxing/csharp/oned/Code39Reader.cs

/*
* 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.
*/
namespace com.google.zxing.oned
{
    using System;
    using System.Text;
    using com.google.zxing.common;


    public sealed class Code39Reader : AbstractOneDReader 
    { 
          private static  String ALPHABET_STRING = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. *$/+%";
          private static  char[] ALPHABET = ALPHABET_STRING.ToCharArray();

          /**
           * These represent the encodings of characters, as patterns of wide and narrow bars.
           * The 9 least-significant bits of each int correspond to the pattern of wide and narrow,
           * with 1s representing "wide" and 0s representing narrow.
           */
          private static  int[] CHARACTER_ENCODINGS = {
              0x034, 0x121, 0x061, 0x160, 0x031, 0x130, 0x070, 0x025, 0x124, 0x064, // 0-9
              0x109, 0x049, 0x148, 0x019, 0x118, 0x058, 0x00D, 0x10C, 0x04C, 0x01C, // A-J
              0x103, 0x043, 0x142, 0x013, 0x112, 0x052, 0x007, 0x106, 0x046, 0x016, // K-T
              0x181, 0x0C1, 0x1C0, 0x091, 0x190, 0x0D0, 0x085, 0x184, 0x0C4, 0x094, // U-*
              0x0A8, 0x0A2, 0x08A, 0x02A // $-%
          };

          private static  int ASTERISK_ENCODING = CHARACTER_ENCODINGS[39];

          private  bool usingCheckDigit;
          private  bool extendedMode;

          /**
           * Creates a reader that assumes all encoded data is data, and does not treat the 
           * character as a check digit. It will not decoded "extended Code 39" sequences.
           */
          public Code39Reader() {
            usingCheckDigit = false;
            extendedMode = false;
          }

          /**
           * Creates a reader that can be configured to check the last character as a check digit.
           * It will not decoded "extended Code 39" sequences.
           *
           * @param usingCheckDigit if true, treat the last data character as a check digit, not
           * data, and verify that the checksum passes.
           */
          public Code39Reader(bool usingCheckDigit) {
            this.usingCheckDigit = usingCheckDigit;
            this.extendedMode = false;
          }

          /**
           * Creates a reader that can be configured to check the last character as a check digit,
           * or optionally attempt to decode "extended Code 39" sequences that are used to encode
           * the full ASCII character set.
           *
           * @param usingCheckDigit if true, treat the last data character as a check digit, not
           * data, and verify that the checksum passes.
           * @param extendedMode if true, will attempt to decode extended Code 39 sequences in the
           * text.
           */
          public Code39Reader(bool usingCheckDigit, bool extendedMode) {
            this.usingCheckDigit = usingCheckDigit;
            this.extendedMode = extendedMode;
          }

          public override Result decodeRow(int rowNumber, BitArray row, System.Collections.Hashtable hints) {

            int[] start = findAsteriskPattern(row);
            int nextStart = start[1];
            int end = row.getSize();

            // Read off white space
            while (nextStart < end && !row.get(nextStart)) {
              nextStart++;
            }

            StringBuilder result = new StringBuilder();
            int[] counters = new int[9];
            char decodedChar;
            int lastStart;
            do {
              recordPattern(row, nextStart, counters);
              int pattern = toNarrowWidePattern(counters);
              decodedChar = patternToChar(pattern);
              result.Append(decodedChar);
              lastStart = nextStart;
              for (int i = 0; i < counters.Length; i++) {
                nextStart += counters[i];
              }
              // Read off white space
              while (nextStart < end && !row.get(nextStart)) {
                nextStart++;
              }
            } while (decodedChar != '*');

            result.Remove(result.Length - 1, 1);  // remove asterisk

            // Look for whitespace after pattern:
            int lastPatternSize = 0;
            for (int i = 0; i < counters.Length; i++) {
              lastPatternSize += counters[i];
            }
            int whiteSpaceAfterEnd = nextStart - lastStart - lastPatternSize;
            // If 50% of last pattern size, following last pattern, is not whitespace, fail
            // (but if it's whitespace to the very end of the image, that's OK)
            if (nextStart != end && whiteSpaceAfterEnd / 2 < lastPatternSize) {
              throw new ReaderException();
            }

            if (usingCheckDigit) {
              int max = result.Length - 1;
              int total = 0;
              for (int i = 0; i < max; i++) {
                total += ALPHABET_STRING.IndexOf(result[i]);
              }
              if (total % 43 != ALPHABET_STRING.IndexOf(result[max]))
              {
                throw new ReaderException();
              }
              result.Remove(max,1);
            }

            String resultString = result.ToString();
            if (extendedMode) {
              resultString = decodeExtended(resultString);
            }

            if (resultString.Length == 0) {
              // Almost surely a false positive
              throw new ReaderException();
            }

            float left = (float) (start[1] + start[0]) / 2.0f;
            float right = (float) (nextStart + lastStart) / 2.0f;
            return new Result(
                resultString,
                null,
                new ResultPoint[]{
                    new GenericResultPoint(left, (float) rowNumber),
                    new GenericResultPoint(right, (float) rowNumber)},
                BarcodeFormat.CODE_39);

          }

          private static int[] findAsteriskPattern(BitArray row) {
            int width = row.getSize();
            int rowOffset = 0;
            while (rowOffset < width) {
              if (row.get(rowOffset)) {
                break;
              }
              rowOffset++;
            }

            int counterPosition = 0;
            int[] counters = new int[9];
            int patternStart = rowOffset;
            bool isWhite = false;
            int patternLength = counters.Length;

            for (int i = rowOffset; i < width; i++) {
              bool pixel = row.get(i);
              if ((!pixel && isWhite) || (pixel && !isWhite)) {
                counters[counterPosition]++;
              } else {
                if (counterPosition == patternLength - 1) {
                  try {
                    if (toNarrowWidePattern(counters) == ASTERISK_ENCODING) {
                      // Look for whitespace before start pattern, >= 50% of width of start pattern
                      if (row.isRange(Math.Max(0, patternStart - (i - patternStart) / 2), patternStart, false)) {
                        return new int[]{patternStart, i};
                      }
                    }
                  } catch (ReaderException re) {
                    // no match, continue
                  }
                  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 new ReaderException();
          }

          private static int toNarrowWidePattern(int[] counters) {
            int numCounters = counters.Length;
            int maxNarrowCounter = 0;
            int wideCounters;
            do {
              int minCounter = int.MaxValue;
              for (int i = 0; i < numCounters; i++) {
                int counter = counters[i];
                if (counter < minCounter && counter > maxNarrowCounter) {
                  minCounter = counter;
                }
              }
              maxNarrowCounter = minCounter;
              wideCounters = 0;
              int totalWideCountersWidth = 0;
              int pattern = 0;
              for (int i = 0; i < numCounters; i++) {
                int counter = counters[i];
                if (counters[i] > maxNarrowCounter) {
                  pattern |= 1 << (numCounters - 1 - i);
                  wideCounters++;
                  totalWideCountersWidth += counter;
                }
              }
              if (wideCounters == 3) {
                // Found 3 wide counters, but are they close enough in width?
                // We can perform a cheap, conservative check to see if any individual
                // counter is more than 1.5 times the average:
                for (int i = 0; i < numCounters && wideCounters > 0; i++) {
                  int counter = counters[i];
                  if (counters[i] > maxNarrowCounter) {
                    wideCounters--;
                    // totalWideCountersWidth = 3 * average, so this checks if counter >= 3/2 * average
                    if ((counter << 1) >= totalWideCountersWidth) {
                      throw new ReaderException();
                    }
                  }
                }
                return pattern;
              }
            } while (wideCounters > 3);
            throw new ReaderException();
          }

          private static char patternToChar(int pattern) {
            for (int i = 0; i < CHARACTER_ENCODINGS.Length; i++) {
              if (CHARACTER_ENCODINGS[i] == pattern) {
                return ALPHABET[i];
              }
            }
            throw new ReaderException();
          }

          private static String decodeExtended(String encoded) {
            int Length = encoded.Length;
            StringBuilder decoded = new StringBuilder(Length);
            for (int i = 0; i < Length; i++) {
              char c = encoded[i];
              if (c == '+' || c == '$' || c == '%' || c == '/') {
                char next = encoded[i + 1];
                char decodedChar = '\0';
                switch (c) {
                  case '+':
                    // +A to +Z map to a to z
                    if (next >= 'A' && next <= 'Z') {
                      decodedChar = (char) (next + 32);
                    } else {
                      throw new ReaderException();
                    }
                    break;
                  case '$':
                    // $A to $Z map to control codes SH to SB
                    if (next >= 'A' && next <= 'Z') {
                      decodedChar = (char) (next - 64);
                    } else {
                      throw new ReaderException();
                    }
                    break;
                  case '%':
                    // %A to %E map to control codes ESC to US
                    if (next >= 'A' && next <= 'E') {
                      decodedChar = (char) (next - 38);
                    } else if (next >= 'F' && next <= 'W') {
                      decodedChar = (char) (next - 11);
                    } else {
                      throw new ReaderException();
                    }
                    break;
                  case '/':
                    // /A to /O map to ! to , and /Z maps to :
                    if (next >= 'A' && next <= 'O') {
                      decodedChar = (char) (next - 32);
                    } else if (next == 'Z') {
                      decodedChar = ':';
                    } else {
                      throw new ReaderException();
                    }
                    break;
                }
                decoded.Append(decodedChar);
                // bump up i again since we read two characters
                i++;
              } else {
                decoded.Append(c);
              }
            }
            return decoded.ToString();
          }

    
    }
}