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Improve QR binary encoding compression

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This commit is contained in:
Gary Sharp
2016-09-21 19:55:00 +10:00
parent 4b866c9486
commit 85425d2a1f
4 changed files with 442 additions and 107 deletions
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Disco.Services/Documents/QRCodeBinaryEncoder.cs
+19 -9
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@@ -19,7 +19,7 @@ namespace Disco.Services.Documents
mode.getCharacterCountBits(ZXing.QrCode.Internal.Version.getVersionForNumber(1)) +
(Content.Length * 8);
var version = ChooseVersion(bitsNeeded, ecLevel);
var version = ChooseVersion(bitsNeeded, out ecLevel);
var ecBlocks = version.getECBlocksForLevel(ecLevel);
var totalByteCapacity = version.TotalCodewords - ecBlocks.TotalECCodewords;
var totalBitCapacity = totalByteCapacity << 3;
@@ -75,8 +75,11 @@ namespace Disco.Services.Documents
return scaleMatrix(matrix.Array, Width, Height);
}
private static ZXing.QrCode.Internal.Version ChooseVersion(int RequiredBits, ErrorCorrectionLevel ECLevel)
private static ZXing.QrCode.Internal.Version ChooseVersion(int RequiredBits, out ErrorCorrectionLevel ECLevel)
{
var ecls = new ErrorCorrectionLevel[] { ErrorCorrectionLevel.H, ErrorCorrectionLevel.Q, ErrorCorrectionLevel.M, ErrorCorrectionLevel.L };
int totalInputBytes = (RequiredBits + 7) / 8;
// In the following comments, we use numbers of Version 7-H.
for (int versionNum = 1; versionNum <= 40; versionNum++)
{
@@ -84,14 +87,21 @@ namespace Disco.Services.Documents
// numBytes = 196
int numBytes = version.TotalCodewords;
// getNumECBytes = 130
var ecBlocks = version.getECBlocksForLevel(ECLevel);
int numEcBytes = ecBlocks.TotalECCodewords;
// getNumDataBytes = 196 - 130 = 66
int numDataBytes = numBytes - numEcBytes;
int totalInputBytes = (RequiredBits + 7) / 8;
if (numDataBytes >= totalInputBytes)
if (numBytes >= totalInputBytes)
{
return version;
for (int ecl = 0; ecl < ecls.Length; ecl++)
{
var ecBlocks = version.getECBlocksForLevel(ecls[ecl]);
int numEcBytes = ecBlocks.TotalECCodewords;
// getNumDataBytes = 196 - 130 = 66
int numDataBytes = numBytes - numEcBytes;
if (numDataBytes >= totalInputBytes)
{
ECLevel = ecls[ecl];
return version;
}
}
}
}
throw new ArgumentException("Data too big", nameof(RequiredBits));