zxing/csharp/oned/ITFReader.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;

/*
 * Copyright 2008 ZXing authors
 *
 * 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 BarcodeFormat = com.google.zxing.BarcodeFormat;
	using DecodeHintType = com.google.zxing.DecodeHintType;
	using FormatException = com.google.zxing.FormatException;
	using NotFoundException = com.google.zxing.NotFoundException;
	using Result = com.google.zxing.Result;
	using ResultPoint = com.google.zxing.ResultPoint;
	using BitArray = com.google.zxing.common.BitArray;


	/// <summary>
	/// <p>Implements decoding of the ITF format, or Interleaved Two of Five.</p>
	/// 
	/// <p>This Reader will scan ITF barcodes of certain lengths only.
	/// At the moment it reads length 6, 10, 12, 14, 16, 24, and 44 as these have appeared "in the wild". Not all
	/// lengths are scanned, especially shorter ones, to avoid false positives. This in turn is due to a lack of
	/// required checksum function.</p>
	/// 
	/// <p>The checksum is optional and is not applied by this Reader. The consumer of the decoded
	/// value will have to apply a checksum if required.</p>
	/// 
	/// <p><a href="http://en.wikipedia.org/wiki/Interleaved_2_of_5">http://en.wikipedia.org/wiki/Interleaved_2_of_5</a>
	/// is a great reference for Interleaved 2 of 5 information.</p>
	/// 
	/// @author kevin.osullivan@sita.aero, SITA Lab.
	/// </summary>
	public sealed class ITFReader : OneDReader
	{

	  private static readonly int MAX_AVG_VARIANCE = (int)(PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.42f);
	  private static readonly int MAX_INDIVIDUAL_VARIANCE = (int)(PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.8f);

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

	  private static readonly int[] DEFAULT_ALLOWED_LENGTHS = {44, 24, 20, 18, 16, 14, 12, 10, 8, 6};

	  // Stores the actual narrow line width of the image being decoded.
	  private int narrowLineWidth = -1;

	  /// <summary>
	  /// Start/end guard pattern.
	  /// 
	  /// Note: The end pattern is reversed because the row is reversed before
	  /// searching for the END_PATTERN
	  /// </summary>
	  private static readonly int[] START_PATTERN = {N, N, N, N};
	  private static readonly int[] END_PATTERN_REVERSED = {N, N, W};

	  /// <summary>
	  /// Patterns of Wide / Narrow lines to indicate each digit
	  /// </summary>
	  internal static readonly int[][] PATTERNS = {new int[] {N, N, W, W, N}, new int[] {W, N, N, N, W}, new int[] {N, W, N, N, W}, new int[] {W, W, N, N, N}, new int[] {N, N, W, N, W}, new int[] {W, N, W, N, N}, new int[] {N, W, W, N, N}, new int[] {N, N, N, W, W}, new int[] {W, N, N, W, N}, new int[] {N, W, N, W, N}};

//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: public com.google.zxing.Result decodeRow(int rowNumber, com.google.zxing.common.BitArray row, java.util.Map<com.google.zxing.DecodeHintType,?> hints) throws com.google.zxing.FormatException, com.google.zxing.NotFoundException
      public override Result decodeRow(int rowNumber, BitArray row, IDictionary<DecodeHintType, object> hints)
	  {

		// Find out where the Middle section (payload) starts & ends
		int[] startRange = decodeStart(row);
		int[] endRange = decodeEnd(row);

		StringBuilder result = new StringBuilder(20);
		decodeMiddle(row, startRange[1], endRange[0], result);
		string resultString = result.ToString();

		int[] allowedLengths = null;
		if (hints != null && hints.ContainsKey(DecodeHintType.ALLOWED_LENGTHS))
		{
		  allowedLengths = (int[]) hints[DecodeHintType.ALLOWED_LENGTHS];

		}
		if (allowedLengths == null)
		{
		  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.Length;
		bool lengthOK = false;
		foreach (int allowedLength in allowedLengths)
		{
		  if (length == allowedLength)
		  {
			lengthOK = true;
			break;
		  }
		}
		if (!lengthOK)
		{
		  throw FormatException.FormatInstance;
		}

		return new Result(resultString, null, new ResultPoint[] {new ResultPoint(startRange[1], (float) rowNumber), new ResultPoint(endRange[0], (float) rowNumber)}, BarcodeFormat.ITF); // no natural byte representation for these barcodes
	  }

	  /// <param name="row">          row of black/white values to search </param>
	  /// <param name="payloadStart"> offset of start pattern </param>
	  /// <param name="resultString"> <seealso cref="StringBuilder"/> to append decoded chars to </param>
	  /// <exception cref="NotFoundException"> if decoding could not complete successfully </exception>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: private static void decodeMiddle(com.google.zxing.common.BitArray row, int payloadStart, int payloadEnd, StringBuilder resultString) throws com.google.zxing.NotFoundException
	  private static void decodeMiddle(BitArray row, int payloadStart, int payloadEnd, StringBuilder 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
		int[] counterDigitPair = new int[10];
		int[] counterBlack = new int[5];
		int[] counterWhite = new int[5];

		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((char)('0' + bestMatch));
		  bestMatch = decodeDigit(counterWhite);
		  resultString.Append((char)('0' + bestMatch));

		  foreach (int counterDigit in counterDigitPair)
		  {
			payloadStart += counterDigit;
		  }
		}
	  }

	  /// <summary>
	  /// Identify where the start of the middle / payload section starts.
	  /// </summary>
	  /// <param name="row"> row of black/white values to search </param>
	  /// <returns> Array, containing index of start of 'start block' and end of
	  ///         'start block' </returns>
	  /// <exception cref="NotFoundException"> </exception>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: int[] decodeStart(com.google.zxing.common.BitArray row) throws com.google.zxing.NotFoundException
	  internal int[] decodeStart(BitArray row)
	  {
		int endStart = skipWhiteSpace(row);
		int[] 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.
		this.narrowLineWidth = (startPattern[1] - startPattern[0]) >> 2;

		validateQuietZone(row, startPattern[0]);

		return startPattern;
	  }

	  /// <summary>
	  /// 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
	  /// </summary>
	  /// <param name="row"> bit array representing the scanned barcode. </param>
	  /// <param name="startPattern"> index into row of the start or end pattern. </param>
	  /// <exception cref="NotFoundException"> if the quiet zone cannot be found, a ReaderException is thrown. </exception>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: private void validateQuietZone(com.google.zxing.common.BitArray row, int startPattern) throws com.google.zxing.NotFoundException
	  private void validateQuietZone(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.NotFoundInstance;
		}
	  }

	  /// <summary>
	  /// Skip all whitespace until we get to the first black line.
	  /// </summary>
	  /// <param name="row"> row of black/white values to search </param>
	  /// <returns> index of the first black line. </returns>
	  /// <exception cref="NotFoundException"> Throws exception if no black lines are found in the row </exception>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: private static int skipWhiteSpace(com.google.zxing.common.BitArray row) throws com.google.zxing.NotFoundException
	  private static int skipWhiteSpace(BitArray row)
	  {
		int width = row.Size;
		int endStart = row.getNextSet(0);
		if (endStart == width)
		{
		  throw NotFoundException.NotFoundInstance;
		}

		return endStart;
	  }

	  /// <summary>
	  /// Identify where the end of the middle / payload section ends.
	  /// </summary>
	  /// <param name="row"> row of black/white values to search </param>
	  /// <returns> Array, containing index of start of 'end block' and end of 'end
	  ///         block' </returns>
	  /// <exception cref="NotFoundException"> </exception>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: int[] decodeEnd(com.google.zxing.common.BitArray row) throws com.google.zxing.NotFoundException
	  internal int[] decodeEnd(BitArray row)
	  {

		// For convenience, reverse the row and then
		// search from 'the start' for the end block
		row.reverse();
		try
		{
		  int endStart = skipWhiteSpace(row);
		  int[] 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.Size - endPattern[1];
		  endPattern[1] = row.Size - temp;

		  return endPattern;
		}
		finally
		{
		  // Put the row back the right way.
		  row.reverse();
		}
	  }

	  /// <param name="row">       row of black/white values to search </param>
	  /// <param name="rowOffset"> position to start search </param>
	  /// <param name="pattern">   pattern of counts of number of black and white pixels that are
	  ///                  being searched for as a pattern </param>
	  /// <returns> start/end horizontal offset of guard pattern, as an array of two
	  ///         ints </returns>
	  /// <exception cref="NotFoundException"> if pattern is not found </exception>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: private static int[] findGuardPattern(com.google.zxing.common.BitArray row, int rowOffset, int[] pattern) throws com.google.zxing.NotFoundException
	  private static int[] findGuardPattern(BitArray row, int rowOffset, int[] pattern)
	  {

		// TODO: This is very similar to implementation in UPCEANReader. Consider if they can be
		// merged to a single method.
		int patternLength = pattern.Length;
		int[] counters = new int[patternLength];
		int width = row.Size;
		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, MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE)
			  {
				return new int[]{patternStart, x};
			  }
			  patternStart += counters[0] + counters[1];
			  Array.Copy(counters, 2, counters, 0, patternLength - 2);
			  counters[patternLength - 2] = 0;
			  counters[patternLength - 1] = 0;
			  counterPosition--;
			}
			else
			{
			  counterPosition++;
			}
			counters[counterPosition] = 1;
			isWhite = !isWhite;
		  }
		}
		throw NotFoundException.NotFoundInstance;
	  }

	  /// <summary>
	  /// Attempts to decode a sequence of ITF black/white lines into single
	  /// digit.
	  /// </summary>
	  /// <param name="counters"> the counts of runs of observed black/white/black/... values </param>
	  /// <returns> The decoded digit </returns>
	  /// <exception cref="NotFoundException"> if digit cannot be decoded </exception>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: private static int decodeDigit(int[] counters) throws com.google.zxing.NotFoundException
	  private static int decodeDigit(int[] counters)
	  {

		int bestVariance = MAX_AVG_VARIANCE; // worst variance we'll accept
		int bestMatch = -1;
		int max = PATTERNS.Length;
		for (int i = 0; i < max; i++)
		{
		  int[] 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.NotFoundInstance;
		}
	  }

	}

}