zxing/csharp/oned/EAN13Reader.cs

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/*
* 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 BarcodeFormat = com.google.zxing.BarcodeFormat;
using ReaderException = com.google.zxing.ReaderException;
using BitArray = com.google.zxing.common.BitArray;
namespace com.google.zxing.oned
{
/// <summary> <p>Implements decoding of the EAN-13 format.</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 sealed class EAN13Reader:UPCEANReader
{
override internal BarcodeFormat BarcodeFormat
{
get
{
return BarcodeFormat.EAN_13;
}
}
// For an EAN-13 barcode, the first digit is represented by the parities used
// to encode the next six digits, according to the table below. For example,
// if the barcode is 5 123456 789012 then the value of the first digit is
// signified by using odd for '1', even for '2', even for '3', odd for '4',
// odd for '5', and even for '6'. See http://en.wikipedia.org/wiki/EAN-13
//
// Parity of next 6 digits
// Digit 0 1 2 3 4 5
// 0 Odd Odd Odd Odd Odd Odd
// 1 Odd Odd Even Odd Even Even
// 2 Odd Odd Even Even Odd Even
// 3 Odd Odd Even Even Even Odd
// 4 Odd Even Odd Odd Even Even
// 5 Odd Even Even Odd Odd Even
// 6 Odd Even Even Even Odd Odd
// 7 Odd Even Odd Even Odd Even
// 8 Odd Even Odd Even Even Odd
// 9 Odd Even Even Odd Even Odd
//
// Note that the encoding for '0' uses the same parity as a UPC barcode. Hence
// a UPC barcode can be converted to an EAN-13 barcode by prepending a 0.
//
// The encoding is represented by the following array, which is a bit pattern
// using Odd = 0 and Even = 1. For example, 5 is represented by:
//
// Odd Even Even Odd Odd Even
// in binary:
// 0 1 1 0 0 1 == 0x19
//
//UPGRADE_NOTE: Final was removed from the declaration of 'FIRST_DIGIT_ENCODINGS'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
internal static readonly int[] FIRST_DIGIT_ENCODINGS = new int[]{0x00, 0x0B, 0x0D, 0xE, 0x13, 0x19, 0x1C, 0x15, 0x16, 0x1A};
//UPGRADE_NOTE: Final was removed from the declaration of 'decodeMiddleCounters '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
private int[] decodeMiddleCounters;
public EAN13Reader()
{
decodeMiddleCounters = new int[4];
}
protected internal override int decodeMiddle(BitArray row, int[] startRange, System.Text.StringBuilder resultString)
{
int[] counters = decodeMiddleCounters;
counters[0] = 0;
counters[1] = 0;
counters[2] = 0;
counters[3] = 0;
int end = row.Size;
int rowOffset = startRange[1];
int lgPatternFound = 0;
for (int x = 0; x < 6 && rowOffset < end; x++)
{
int bestMatch = decodeDigit(row, counters, rowOffset, L_AND_G_PATTERNS);
resultString.Append((char) ('0' + bestMatch % 10));
for (int i = 0; i < counters.Length; i++)
{
rowOffset += counters[i];
}
if (bestMatch >= 10)
{
lgPatternFound |= 1 << (5 - x);
}
}
determineFirstDigit(resultString, lgPatternFound);
int[] middleRange = findGuardPattern(row, rowOffset, true, MIDDLE_PATTERN);
rowOffset = middleRange[1];
for (int x = 0; x < 6 && rowOffset < end; x++)
{
int bestMatch = decodeDigit(row, counters, rowOffset, L_PATTERNS);
resultString.Append((char) ('0' + bestMatch));
for (int i = 0; i < counters.Length; i++)
{
rowOffset += counters[i];
}
}
return rowOffset;
}
/// <summary> Based on pattern of odd-even ('L' and 'G') patterns used to encoded the explicitly-encoded
/// digits in a barcode, determines the implicitly encoded first digit and adds it to the
/// result string.
///
/// </summary>
/// <param name="resultString">string to insert decoded first digit into
/// </param>
/// <param name="lgPatternFound">int whose bits indicates the pattern of odd/even L/G patterns used to
/// encode digits
/// </param>
/// <throws> ReaderException if first digit cannot be determined </throws>
private static void determineFirstDigit(System.Text.StringBuilder resultString, int lgPatternFound)
{
for (int d = 0; d < 10; d++)
{
if (lgPatternFound == FIRST_DIGIT_ENCODINGS[d])
{
resultString.Insert(0, (char) ('0' + d));
return ;
}
}
throw ReaderException.Instance;
}
}
}