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Decode fix for CCITTFax Group 3 (1 dimensional version)

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This commit is contained in:
Kasper Frank
2021-05-09 18:45:26 +02:00
parent 264cf7b8a8
commit 30039aa6d3
3 changed files with 17 additions and 27 deletions
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14
src/UglyToad.PdfPig/Filters/CcittFaxCompressionType.cs
View File

@@ -6,16 +6,20 @@
internal enum CcittFaxCompressionType
{
/// <summary>
/// Modified Huffman - Group 3 (T4)
/// Modified Huffman (MH) - Group 3 variation (T2)
/// </summary>
ModifiedHuffman,
/// <summary>
/// Modified Read - Group 3 (optional T4)
/// Modified Huffman (MH) - Group 3 (T4)
/// </summary>
T4,
Group3_1D,
/// <summary>
/// Modified Modified Read - Group 4 (T6)
/// Modified Read (MR) - Group 3 (T4)
/// </summary>
T6
Group3_2D,
/// <summary>
/// Modified Modified Read (MMR) - Group 4 (T6)
/// </summary>
Group4_2D
}
}

8
src/UglyToad.PdfPig/Filters/CcittFaxDecodeFilter.cs
View File

@@ -60,7 +60,7 @@
{
if (k == 0)
{
var compressionType = CcittFaxCompressionType.T4; // Group 3 1D
var compressionType = CcittFaxCompressionType.Group3_1D; // Group 3 1D
if (input.Count < 20)
{
@@ -78,7 +78,7 @@
b = (short)((b << 1) + ((input[(i / 8)] >> (7 - (i % 8))) & 0x01));
if ((b & 0xFFF) == 1)
{
return CcittFaxCompressionType.T4;
return CcittFaxCompressionType.Group3_1D;
}
}
}
@@ -88,11 +88,11 @@
else if (k > 0)
{
// Group 3 2D
return CcittFaxCompressionType.T4;
return CcittFaxCompressionType.Group3_2D;
}
else
{
return CcittFaxCompressionType.T6;
return CcittFaxCompressionType.Group4_2D;
}
}

22
src/UglyToad.PdfPig/Filters/CcittFaxDecoderStream.cs
View File

@@ -17,7 +17,6 @@
private readonly int columns;
private readonly byte[] decodedRow;
private readonly bool optionG32D;
private readonly bool optionByteAligned;
private readonly CcittFaxCompressionType type;
@@ -52,20 +51,6 @@
changesCurrentRow = new int[columns + 2];
optionByteAligned = byteAligned;
switch (type)
{
case CcittFaxCompressionType.ModifiedHuffman:
optionG32D = false;
break;
case CcittFaxCompressionType.T4:
optionG32D = true;
break;
case CcittFaxCompressionType.T6:
optionG32D = false;
break;
default:
throw new ArgumentOutOfRangeException(nameof(type), type, "Illegal parameter");
}
}
private void Fetch()
@@ -252,7 +237,7 @@
}
done:
if (!optionG32D || ReadBit())
if (type == CcittFaxCompressionType.Group3_1D || ReadBit())
{
Decode1D();
}
@@ -279,10 +264,11 @@
case CcittFaxCompressionType.ModifiedHuffman:
DecodeRowType2();
break;
case CcittFaxCompressionType.T4:
case CcittFaxCompressionType.Group3_1D:
case CcittFaxCompressionType.Group3_2D:
DecodeRowType4();
break;
case CcittFaxCompressionType.T6:
case CcittFaxCompressionType.Group4_2D:
DecodeRowType6();
break;
default: