private void WritePixelRun(Span <byte> buffer, T4BitReader bitReader, uint bitsWritten)
{
if (bitReader.IsWhiteRun)
{
BitWriterUtils.WriteBits(buffer, (int)bitsWritten, bitReader.RunLength, this.whiteValue);
}
else
{
BitWriterUtils.WriteBits(buffer, (int)bitsWritten, bitReader.RunLength, this.blackValue);
}
}
/// <inheritdoc/>
protected override void Decompress(BufferedReadStream stream, int byteCount, int stripHeight, Span <byte> buffer)
{
if (this.faxCompressionOptions.HasFlag(FaxCompressionOptions.TwoDimensionalCoding))
{
TiffThrowHelper.ThrowNotSupported("TIFF CCITT 2D compression is not yet supported");
}
bool eolPadding = this.faxCompressionOptions.HasFlag(FaxCompressionOptions.EolPadding);
using var bitReader = new T4BitReader(stream, this.FillOrder, byteCount, this.Allocator, eolPadding);
buffer.Clear();
uint bitsWritten = 0;
uint pixelWritten = 0;
while (bitReader.HasMoreData)
{
bitReader.ReadNextRun();
if (bitReader.RunLength > 0)
{
this.WritePixelRun(buffer, bitReader, bitsWritten);
bitsWritten += bitReader.RunLength;
pixelWritten += bitReader.RunLength;
}
if (bitReader.IsEndOfScanLine)
{
// Write padding bytes, if necessary.
uint pad = 8 - (bitsWritten % 8);
if (pad != 8)
{
BitWriterUtils.WriteBits(buffer, (int)bitsWritten, pad, 0);
bitsWritten += pad;
}
pixelWritten = 0;
}
}
// Edge case for when we are at the last byte, but there are still some unwritten pixels left.
if (pixelWritten > 0 && pixelWritten < this.width)
{
bitReader.ReadNextRun();
this.WritePixelRun(buffer, bitReader, bitsWritten);
}
}
