TheXamlGuy
115 lines
3.0 KiB
C#
115 lines
3.0 KiB
C#
using System;
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using Gma.QrCodeNet.Encoding.Masking;
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namespace Gma.QrCodeNet.Encoding.EncodingRegion;
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/// <summary>
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/// 6.9 Format information
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/// The Format Information is a 15 bit sequence containing 5 data bits, with 10 error correction bits calculated using the (15, 5) BCH code.
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/// </summary>
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/// <remarks>ISO/IEC 18004:2000 Chapter 8.9 Page 53</remarks>
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internal static class FormatInformation
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{
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/// <summary>
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/// From Appendix C in JISX0510:2004 (p.65).
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/// </summary>
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private const int FormatInfoPoly = 0x537;
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/// <summary>
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/// From Appendix C in JISX0510:2004 (p.65).
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/// </summary>
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private const int FormatInfoMaskPattern = 0x5412;
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/// <summary>
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/// Embed format information to tristatematrix.
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/// Process combination of create info bits, BCH error correction bits calculation, embed towards matrix.
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/// </summary>
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/// <remarks>ISO/IEC 18004:2000 Chapter 8.9 Page 53</remarks>
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internal static void EmbedFormatInformation(this TriStateMatrix triMatrix, ErrorCorrectionLevel errorLevel, Pattern pattern)
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{
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BitList formatInfo = GetFormatInfoBits(errorLevel, pattern);
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int width = triMatrix.Width;
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for (int index = 0; index < 15; index++)
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{
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MatrixPoint point = PointForInfo1(index);
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bool bit = formatInfo[index];
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triMatrix[point.X, point.Y, MatrixStatus.NoMask] = bit;
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if (index < 7)
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{
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triMatrix[8, width - 1 - index, MatrixStatus.NoMask] = bit;
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}
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else
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{
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triMatrix[width - 8 + (index - 7), 8, MatrixStatus.NoMask] = bit;
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}
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}
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}
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private static MatrixPoint PointForInfo1(int bitsIndex)
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{
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if (bitsIndex <= 7)
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{
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return bitsIndex >= 6
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? new MatrixPoint(bitsIndex + 1, 8)
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: new MatrixPoint(bitsIndex, 8);
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}
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else
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{
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return bitsIndex == 8
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? new MatrixPoint(8, 8 - (bitsIndex - 7))
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: new MatrixPoint(8, 8 - (bitsIndex - 7) - 1);
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}
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}
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private static BitList GetFormatInfoBits(ErrorCorrectionLevel errorLevel, Pattern pattern)
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{
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int formatInfo = (int)pattern.MaskPatternType;
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// Pattern bits length = 3
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formatInfo |= GetErrorCorrectionIndicatorBits(errorLevel) << 3;
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int bchCode = BCHCalculator.CalculateBCH(formatInfo, FormatInfoPoly);
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// bchCode length = 10
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formatInfo = (formatInfo << 10) | bchCode;
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// xor maskPattern
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formatInfo ^= FormatInfoMaskPattern;
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BitList resultBits = new()
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{
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{ formatInfo, 15 }
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};
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if (resultBits.Count != 15)
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{
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throw new Exception("FormatInfoBits length is not 15");
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}
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else
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{
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return resultBits;
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}
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}
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/// <summary>
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/// According Table 25 — Error correction level indicators
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/// Using these bits as enum values would destroy their order which currently corresponds to error correction strength.
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/// </summary>
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internal static int GetErrorCorrectionIndicatorBits(ErrorCorrectionLevel errorLevel)
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{
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// L 01
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// M 00
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// Q 11
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// H 10
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return errorLevel switch
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{
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ErrorCorrectionLevel.H => 0x02,
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ErrorCorrectionLevel.L => 0x01,
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ErrorCorrectionLevel.M => 0x00,
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ErrorCorrectionLevel.Q => 0x03,
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_ => throw new ArgumentException($"Unsupported error correction level [{errorLevel}]", nameof(errorLevel))
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};
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}
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}
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