/// <inheritdoc />
public void Compress(TiffCompressionContext context, ReadOnlyMemory <byte> input, IBufferWriter <byte> outputWriter)
{
if (context is null)
{
throw new ArgumentNullException(nameof(context));
}
if (context.PhotometricInterpretation != TiffPhotometricInterpretation.WhiteIsZero && context.PhotometricInterpretation != TiffPhotometricInterpretation.BlackIsZero)
{
throw new NotSupportedException("Modified Huffman compression does not support this photometric interpretation.");
}
if (context.BitsPerSample.Count != 1 || context.BitsPerSample[0] != 8)
{
throw new NotSupportedException("Unsupported bits per sample.");
}
context.BitsPerSample = TiffValueCollection.Single <ushort>(1);
ReadOnlySpan <byte> inputSpan = input.Span;
int width = context.ImageSize.Width;
int height = context.ImageSize.Height;
var bitWriter = new BitWriter2(outputWriter, 4096);
// Process every scanline
for (int row = 0; row < height; row++)
{
ReadOnlySpan <byte> rowSpan = inputSpan.Slice(0, width);
inputSpan = inputSpan.Slice(width);
CcittEncodingTable currentTable = CcittEncodingTable.WhiteInstance;
CcittEncodingTable otherTable = CcittEncodingTable.BlackInstance;
// ModifiedHuffman compression assumes WhiteIsZero photometric interpretation is used.
// Since the first run is white run, we look for black pixel in the first iteration.
byte nextRunPixel = 255;
while (!rowSpan.IsEmpty)
{
// Get the length of the current run
int runLength = rowSpan.IndexOf(nextRunPixel);
if (runLength < 0)
{
runLength = rowSpan.Length;
}
currentTable.EncodeRun(ref bitWriter, runLength);
rowSpan = rowSpan.Slice(runLength);
// Switch to the other color
CcittHelper.SwapTable(ref currentTable, ref otherTable);
nextRunPixel = (byte)~nextRunPixel;
}
bitWriter.AdvanceAlignByte();
}
bitWriter.Flush();
}
/// <inheritdoc />
public void Compress(TiffCompressionContext context, ReadOnlyMemory <byte> input, IBufferWriter <byte> outputWriter)
{
if (context is null)
{
throw new ArgumentNullException(nameof(context));
}
if (context.PhotometricInterpretation != TiffPhotometricInterpretation.WhiteIsZero && context.PhotometricInterpretation != TiffPhotometricInterpretation.BlackIsZero)
{
throw new NotSupportedException("Modified Huffman compression does not support this photometric interpretation.");
}
if (context.BitsPerSample.Count != 1 || context.BitsPerSample[0] != 8)
{
throw new NotSupportedException("Unsupported bits per sample.");
}
context.BitsPerSample = TiffValueCollection.Single <ushort>(1);
ReadOnlySpan <byte> inputSpan = input.Span;
int width = context.ImageSize.Width;
int height = context.ImageSize.Height;
var bitWriter = new BitWriter2(outputWriter, 4096);
ReferenceScanline referenceScanline = new ReferenceScanline(whiteIsZero: true, width);
// Process every scanline
for (int row = 0; row < height; row++)
{
ReadOnlySpan <byte> scanline = inputSpan.Slice(0, width);
inputSpan = inputSpan.Slice(width);
Encode2DScanline(ref bitWriter, referenceScanline, scanline);
referenceScanline = new ReferenceScanline(whiteIsZero: true, scanline);
}
bitWriter.Flush();
}
