private void WriteCode(uint codeLength, uint code, Span <byte> compressedData)
{
while (codeLength > 0)
{
int bitNumber = (int)codeLength;
bool bit = (code & (1 << (bitNumber - 1))) != 0;
if (bit)
{
BitWriterUtils.WriteBit(compressedData, this.bytePosition, this.bitPosition);
}
else
{
BitWriterUtils.WriteZeroBit(compressedData, this.bytePosition, this.bitPosition);
}
this.bitPosition++;
if (this.bitPosition == 8)
{
this.bytePosition++;
this.bitPosition = 0;
}
codeLength--;
}
}
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);
}
}
/// <inheritdoc/>
protected override void Decompress(BufferedReadStream stream, int byteCount, int stripHeight, Span <byte> buffer)
{
using var bitReader = new ModifiedHuffmanBitReader(stream, this.FillOrder, byteCount, this.Allocator);
buffer.Clear();
uint bitsWritten = 0;
uint pixelsWritten = 0;
while (bitReader.HasMoreData)
{
bitReader.ReadNextRun();
if (bitReader.RunLength > 0)
{
if (bitReader.IsWhiteRun)
{
BitWriterUtils.WriteBits(buffer, (int)bitsWritten, bitReader.RunLength, this.whiteValue);
}
else
{
BitWriterUtils.WriteBits(buffer, (int)bitsWritten, bitReader.RunLength, this.blackValue);
}
bitsWritten += bitReader.RunLength;
pixelsWritten += bitReader.RunLength;
}
if (pixelsWritten == this.Width)
{
bitReader.StartNewRow();
pixelsWritten = 0;
// Write padding bits, if necessary.
uint pad = 8 - (bitsWritten % 8);
if (pad != 8)
{
BitWriterUtils.WriteBits(buffer, (int)bitsWritten, pad, 0);
bitsWritten += pad;
}
}
if (pixelsWritten > this.Width)
{
TiffThrowHelper.ThrowImageFormatException("ccitt compression parsing error, decoded more pixels then image width");
}
}
}
private uint WriteScanLine(Span <byte> buffer, Span <byte> scanLine, uint bitsWritten)
{
byte white = (byte)(this.isWhiteZero ? 0 : 255);
for (int i = 0; i < scanLine.Length; i++)
{
BitWriterUtils.WriteBits(buffer, (int)bitsWritten, 1, scanLine[i] == white ? this.whiteValue : this.blackValue);
bitsWritten++;
}
// Write padding bytes, if necessary.
uint remainder = bitsWritten % 8;
if (remainder != 0)
{
uint padding = 8 - remainder;
BitWriterUtils.WriteBits(buffer, (int)bitsWritten, padding, 0);
bitsWritten += padding;
}
return(bitsWritten);
}
