zxing/csharp/oned/UPCEANReader.cs

/*
* 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.
*/
using System;
using ReaderException = com.google.zxing.ReaderException;
using Result = com.google.zxing.Result;
using ResultPointCallback = com.google.zxing.ResultPointCallback;
using DecodeHintType = com.google.zxing.DecodeHintType;
using ResultPoint = com.google.zxing.ResultPoint;
using BarcodeFormat = com.google.zxing.BarcodeFormat;
using BitArray = com.google.zxing.common.BitArray;
namespace com.google.zxing.oned
{
	
	/// <summary> <p>Encapsulates functionality and implementation that is common to UPC and EAN families
	/// of one-dimensional barcodes.</p>
	/// 
	/// </summary>
	/// <author>  dswitkin@google.com (Daniel Switkin)
	/// </author>
	/// <author>  Sean Owen
	/// </author>
	/// <author>  alasdair@google.com (Alasdair Mackintosh)
	/// </author>
	/// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source 
	/// </author>
	public abstract class UPCEANReader:OneDReader
	{
		/// <summary> Get the format of this decoder.
		/// 
		/// </summary>
		/// <returns> The 1D format.
		/// </returns>
		internal abstract BarcodeFormat BarcodeFormat{get;}
		
		// These two values are critical for determining how permissive the decoding will be.
		// We've arrived at these values through a lot of trial and error. Setting them any higher
		// lets false positives creep in quickly.
		//UPGRADE_NOTE: Final was removed from the declaration of 'MAX_AVG_VARIANCE '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
		//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
		private static readonly int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.42f);
		//UPGRADE_NOTE: Final was removed from the declaration of 'MAX_INDIVIDUAL_VARIANCE '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
		//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
		private static readonly int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.7f);
		
		/// <summary> Start/end guard pattern.</summary>
		//UPGRADE_NOTE: Final was removed from the declaration of 'START_END_PATTERN'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
		internal static readonly int[] START_END_PATTERN = new int[]{1, 1, 1};
		
		/// <summary> Pattern marking the middle of a UPC/EAN pattern, separating the two halves.</summary>
		//UPGRADE_NOTE: Final was removed from the declaration of 'MIDDLE_PATTERN'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
		internal static readonly int[] MIDDLE_PATTERN = new int[]{1, 1, 1, 1, 1};
		
		/// <summary> "Odd", or "L" patterns used to encode UPC/EAN digits.</summary>
		//UPGRADE_NOTE: Final was removed from the declaration of 'L_PATTERNS'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
		internal static readonly int[][] L_PATTERNS = new int[][]{new int[]{3, 2, 1, 1}, new int[]{2, 2, 2, 1}, new int[]{2, 1, 2, 2}, new int[]{1, 4, 1, 1}, new int[]{1, 1, 3, 2}, new int[]{1, 2, 3, 1}, new int[]{1, 1, 1, 4}, new int[]{1, 3, 1, 2}, new int[]{1, 2, 1, 3}, new int[]{3, 1, 1, 2}};
		
		/// <summary> As above but also including the "even", or "G" patterns used to encode UPC/EAN digits.</summary>
		internal static int[][] L_AND_G_PATTERNS;
		
		//UPGRADE_NOTE: Final was removed from the declaration of 'decodeRowStringBuffer '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
		private System.Text.StringBuilder decodeRowStringBuffer;
		
		protected internal UPCEANReader()
		{
			decodeRowStringBuffer = new System.Text.StringBuilder(20);
		}
		
		internal static int[] findStartGuardPattern(BitArray row)
		{
			bool foundStart = false;
			int[] startRange = null;
			int nextStart = 0;
			while (!foundStart)
			{
				startRange = findGuardPattern(row, nextStart, false, START_END_PATTERN);
				int start = startRange[0];
				nextStart = startRange[1];
				// Make sure there is a quiet zone at least as big as the start pattern before the barcode.
				// If this check would run off the left edge of the image, do not accept this barcode,
				// as it is very likely to be a false positive.
				int quietStart = start - (nextStart - start);
				if (quietStart >= 0)
				{
					foundStart = row.isRange(quietStart, start, false);
				}
			}
			return startRange;
		}
		
		public override Result decodeRow(int rowNumber, BitArray row, System.Collections.Hashtable hints)
		{
			return decodeRow(rowNumber, row, findStartGuardPattern(row), hints);
		}
		
		/// <summary> <p>Like {@link #decodeRow(int, BitArray, java.util.Hashtable)}, but
		/// allows caller to inform method about where the UPC/EAN start pattern is
		/// found. This allows this to be computed once and reused across many implementations.</p>
		/// </summary>
		public virtual Result decodeRow(int rowNumber, BitArray row, int[] startGuardRange, System.Collections.Hashtable hints)
		{
			
			ResultPointCallback resultPointCallback = hints == null?null:(ResultPointCallback) hints[DecodeHintType.NEED_RESULT_POINT_CALLBACK];
			
			if (resultPointCallback != null)
			{
				resultPointCallback.foundPossibleResultPoint(new ResultPoint((startGuardRange[0] + startGuardRange[1]) / 2.0f, rowNumber));
			}
			
			System.Text.StringBuilder result = decodeRowStringBuffer;
			result.Length = 0;
			int endStart = decodeMiddle(row, startGuardRange, result);
			
			if (resultPointCallback != null)
			{
				resultPointCallback.foundPossibleResultPoint(new ResultPoint(endStart, rowNumber));
			}
			
			int[] endRange = decodeEnd(row, endStart);
			
			if (resultPointCallback != null)
			{
				resultPointCallback.foundPossibleResultPoint(new ResultPoint((endRange[0] + endRange[1]) / 2.0f, rowNumber));
			}
			
			
			// Make sure there is a quiet zone at least as big as the end pattern after the barcode. The
			// spec might want more whitespace, but in practice this is the maximum we can count on.
			int end = endRange[1];
			int quietEnd = end + (end - endRange[0]);
			if (quietEnd >= row.Size || !row.isRange(end, quietEnd, false))
			{
				throw ReaderException.Instance;
			}
			
			System.String resultString = result.ToString();
			if (!checkChecksum(resultString))
			{
				throw ReaderException.Instance;
			}
			
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			float left = (float) (startGuardRange[1] + startGuardRange[0]) / 2.0f;
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			float right = (float) (endRange[1] + endRange[0]) / 2.0f;
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			return new Result(resultString, null, new ResultPoint[]{new ResultPoint(left, (float) rowNumber), new ResultPoint(right, (float) rowNumber)}, BarcodeFormat);
		}
		
		/// <returns> {@link #checkStandardUPCEANChecksum(String)}
		/// </returns>
		//UPGRADE_NOTE: Access modifiers of method 'checkChecksum' were changed to 'protected'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1204'"
		protected internal virtual bool checkChecksum(System.String s)
		{
			return checkStandardUPCEANChecksum(s);
		}
		
		/// <summary> Computes the UPC/EAN checksum on a string of digits, and reports
		/// whether the checksum is correct or not.
		/// 
		/// </summary>
		/// <param name="s">string of digits to check
		/// </param>
		/// <returns> true iff string of digits passes the UPC/EAN checksum algorithm
		/// </returns>
		/// <throws>  ReaderException if the string does not contain only digits </throws>
		private static bool checkStandardUPCEANChecksum(System.String s)
		{
			int length = s.Length;
			if (length == 0)
			{
				return false;
			}
			
			int sum = 0;
			for (int i = length - 2; i >= 0; i -= 2)
			{
				int digit = (int) s[i] - (int) '0';
				if (digit < 0 || digit > 9)
				{
					throw ReaderException.Instance;
				}
				sum += digit;
			}
			sum *= 3;
			for (int i = length - 1; i >= 0; i -= 2)
			{
				int digit = (int) s[i] - (int) '0';
				if (digit < 0 || digit > 9)
				{
					throw ReaderException.Instance;
				}
				sum += digit;
			}
			return sum % 10 == 0;
		}
		
		//UPGRADE_NOTE: Access modifiers of method 'decodeEnd' were changed to 'protected'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1204'"
		protected internal virtual int[] decodeEnd(BitArray row, int endStart)
		{
			return findGuardPattern(row, endStart, false, START_END_PATTERN);
		}
		
		/// <param name="row">row of black/white values to search
		/// </param>
		/// <param name="rowOffset">position to start search
		/// </param>
		/// <param name="whiteFirst">if true, indicates that the pattern specifies white/black/white/...
		/// pixel counts, otherwise, it is interpreted as black/white/black/...
		/// </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>
		/// <throws>  ReaderException if pattern is not found </throws>
		internal static int[] findGuardPattern(BitArray row, int rowOffset, bool whiteFirst, int[] pattern)
		{
			int patternLength = pattern.Length;
			int[] counters = new int[patternLength];
			int width = row.Size;
			bool isWhite = false;
			while (rowOffset < width)
			{
				isWhite = !row.get_Renamed(rowOffset);
				if (whiteFirst == isWhite)
				{
					break;
				}
				rowOffset++;
			}
			
			int counterPosition = 0;
			int patternStart = rowOffset;
			for (int x = rowOffset; x < width; x++)
			{
				bool pixel = row.get_Renamed(x);
				if (pixel ^ 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];
						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 ReaderException.Instance;
		}
		
		/// <summary> Attempts to decode a single UPC/EAN-encoded digit.
		/// 
		/// </summary>
		/// <param name="row">row of black/white values to decode
		/// </param>
		/// <param name="counters">the counts of runs of observed black/white/black/... values
		/// </param>
		/// <param name="rowOffset">horizontal offset to start decoding from
		/// </param>
		/// <param name="patterns">the set of patterns to use to decode -- sometimes different encodings
		/// for the digits 0-9 are used, and this indicates the encodings for 0 to 9 that should
		/// be used
		/// </param>
		/// <returns> horizontal offset of first pixel beyond the decoded digit
		/// </returns>
		/// <throws>  ReaderException if digit cannot be decoded </throws>
		internal static int decodeDigit(BitArray row, int[] counters, int rowOffset, int[][] patterns)
		{
			recordPattern(row, rowOffset, 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 ReaderException.Instance;
			}
		}
		
		/// <summary> Subclasses override this to decode the portion of a barcode between the start
		/// and end guard patterns.
		/// 
		/// </summary>
		/// <param name="row">row of black/white values to search
		/// </param>
		/// <param name="startRange">start/end offset of start guard pattern
		/// </param>
		/// <param name="resultString">{@link StringBuffer} to append decoded chars to
		/// </param>
		/// <returns> horizontal offset of first pixel after the "middle" that was decoded
		/// </returns>
		/// <throws>  ReaderException if decoding could not complete successfully </throws>
		protected internal abstract int decodeMiddle(BitArray row, int[] startRange, System.Text.StringBuilder resultString);
		static UPCEANReader()
		{
			{
				L_AND_G_PATTERNS = new int[20][];
				for (int i = 0; i < 10; i++)
				{
					L_AND_G_PATTERNS[i] = L_PATTERNS[i];
				}
				for (int i = 10; i < 20; i++)
				{
					int[] widths = L_PATTERNS[i - 10];
					int[] reversedWidths = new int[widths.Length];
					for (int j = 0; j < widths.Length; j++)
					{
						reversedWidths[j] = widths[widths.Length - j - 1];
					}
					L_AND_G_PATTERNS[i] = reversedWidths;
				}
			}
		}
	}
}